Contact Details
Michael G. Ruppert
School of Electrical Engineering and Computing
The University of Newcastle
Callaghan, NSW 2308, Australia
+61 2 4921 7345
Michael(dot)Ruppert(at)newcastle.edu.au
Biography
Michael Ruppert received the Dipl.-Ing. Degree in automation technology in production, with a specialization in systems theory and automatic control, from the University of Stuttgart, Germany, in 2013. In 2017, he received the Ph.D. degree with Excellence Award in electrical engineering from The University of Newcastle, Australia where he is now a Postdoctoral Research Fellow with the School of Electrical Engineering and Computing.
Dr Ruppert’s research topics are situated within the area of Micro Precision Mechatronics and as such bridge the gap between classical electrical / control engineering and emerging applications in the field of microelectromechanical systems, high performance microscopy and nanotechnology. His recent work has focused on the development of estimation, control and self-sensing approaches for microelectromechanical (MEMS) systems such as piezoelectric microcantilevers and nanopositioning systems for multifrequency and single-chip atomic force microscopy.
As a Visiting Researcher, he was with the Mechanical Engineering Department, University of Texas at Dallas, USA. During his research visit he worked on the fabrication of piezoelectric microcantilevers in the clean room and lead-authored the publication on the first silicon-on-insulator MEMS on-chip atomic force microscope, recently published and identified as a JMEMS RightNow paper in the IEEE Journal of Microelectromechanical Systems, and which was highlighted in the IEEE Spectrum magazine. During his visit, Dr. Ruppert also consulted to Zyvex LABS, Richardson, USA on the analysis of process stability of scanning tunneling microscope enabled nanolithography.
Dr Ruppert received the Academic Merit Scholarship from the University of Stuttgart, the Baden-Württemberg Scholarship, and held Postgraduate Research Scholarships with the University of Newcastle and with the CSIRO, Clayton, VIC, Australia. Dr Ruppert’s research has been recognized with Best Conference Paper Finalist Awards at the 2018 International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS) and a the 2013 IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM). In 2018, the article Multimode Q Control in Tapping-Mode AFM: Enabling Imaging on Higher Flexural Eigenmodes published in IEEE Transactions on Control Systems Technology received the 2018 IEEE TCST Outstanding Paper Award.
Professional Activities
Editorial and Reviewer Roles
- 2020-present: Associate Editor for IEEE Control Systems Letters
- 2020-present: Program Committee for MARSS
- 2018-present: IEEE Control Systems Society Conference Editorial Board: Associate Editor for ACC2019, CDC2019, ACC2020
- 2018-present: Detailed assessor for ARC grant proposals.
- 2013-present: Reviewer for Journals IEEE TNANO, IEEE TMEC, IEEE TCST, IEEE JMEMS, AJC
Organization of Special Session
Theme: Design and Control of Micro and Nano Precision Mechatronic Systems
- July 2019: International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS), Helsinki, Finland
- July 2018: IEEE Advanced Intelligent Mechatronics (AIM), Auckland, New Zealand, 2018
- July 2017: IEEE Advanced Intelligent Mechatronics (AIM), Munich, Germany, 2017
Speaker Invitations
- April 2018: Invited seminars at EPFL, Switzerland and TNO, The Netherlands on ‘Integrated Sensing, Estimation and Control in Multifrequency Atomic Force Microscopy’
- May 2017: IEEE Seminar at University of Western Australia on ‘Self-Sensing, Estimation and Control in Multifrequency Atomic Force Microscopy’
Awards, Prizes and Scholarships
Awards
- 2019 Best Conference Paper, IEEE MARSS Conference
- 2018 IEEE TCST Outstanding Paper Award, IEEE Control Systems Society
- 2018 Best Conference Paper Finalist, IEEE MARSS Conference
- 2017 HDR Excellence Award, The University of Newcastle
- 2013 Best Student Conference Paper Finalist, IEEE/ASME AIM International Conference
Prizes
- 2016 FEBE Postgraduate Research Prize, The University of Newcastle
- 2015 Student Paper Competition, Zurich Instruments AG
- 2014 FEBE Postgraduate Research Prize, The University of Newcastle
Publications
2020 |
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| 40. |  | M. G. Ruppert; N. J. Bartlett; Y. K. Yong; A. J. Fleming Amplitude Noise Spectrum of a Lock-in Amplifier: Application to Microcantilever Noise Measurements Journal Article Sensors and Actuators A: Physical, 2020. @article{Ruppert2020, title = {Amplitude Noise Spectrum of a Lock-in Amplifier: Application to Microcantilever Noise Measurements}, author = {M. G. Ruppert and N. J. Bartlett and Y. K. Yong and A. J. Fleming}, url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2020/06/1-s2.0-S0924424719322873-main.pdf}, doi = {10.1016/j.sna.2020.112092}, year = {2020}, date = {2020-05-29}, journal = {Sensors and Actuators A: Physical}, abstract = {The lock-in amplifier is a crucial component in many applications requiring high-resolution displacement sensing; it's purpose is to estimate the amplitude and phase of a periodic signal, potentially corrupted by noise, at a frequency determined by a reference signal. Where the noise can be approximated by a stationary Gaussian process, such as thermal force noise and electronic sensor noise, this article derives the amplitude noise spectral density of the lock-in-amplifier output. The proposed method is demonstrated by predicting the demodulated noise spectrum of a microcantilever for dynamic-mode atomic force microscopy to determine the cantilever on-resonance thermal noise, the cantilever tracking bandwidth and the electronic noise floor. The estimates are shown to closely match experimental results over a wide range of operating conditions.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The lock-in amplifier is a crucial component in many applications requiring high-resolution displacement sensing; it's purpose is to estimate the amplitude and phase of a periodic signal, potentially corrupted by noise, at a frequency determined by a reference signal. Where the noise can be approximated by a stationary Gaussian process, such as thermal force noise and electronic sensor noise, this article derives the amplitude noise spectral density of the lock-in-amplifier output. The proposed method is demonstrated by predicting the demodulated noise spectrum of a microcantilever for dynamic-mode atomic force microscopy to determine the cantilever on-resonance thermal noise, the cantilever tracking bandwidth and the electronic noise floor. The estimates are shown to closely match experimental results over a wide range of operating conditions. |
| 39. |  | S. I. Moore; M. G. Ruppert; Y. K. Yong AFM Cantilever Design for Multimode Q Control: Arbitrary Placement of Higher-Order Modes Journal Article IEEE/ASME Transactions on Mechatronics, pp. 1-6, 2020, (Early Access). @article{Moore2020, title = {AFM Cantilever Design for Multimode Q Control: Arbitrary Placement of Higher-Order Modes}, author = {S. I. Moore and M. G. Ruppert and Y. K. Yong}, url = {https://ieeexplore.ieee.org/document/9006926}, doi = {10.1109/TMECH.2020.2975627}, year = {2020}, date = {2020-02-21}, journal = { IEEE/ASME Transactions on Mechatronics}, pages = {1-6}, abstract = {In the fast growing field of multifrequency atomic force microscopy (AFM), the benefits of using higher-order modes has been extensively reported on. However, higher modes of AFM cantilevers are difficult to instrument and Q control is challenging owing to their high frequency nature. At these high frequencies, the latencies in the computations and analog conversions of digital signal processing platforms become significant and limit the effective bandwidth of digital feedback controller implementations. To address this issue, this article presents a novel cantilever design for which the first five modes are placed within a 200 kHz bandwidth. The proposed cantilever is designed using a structural optimization routine. The close spacing and low mechanical bandwidth of the resulting cantilever allows for the implementation of Q controllers for all five modes using a standard FPGA development board for bimodal AFM and imaging on higher-order modes.}, note = {Early Access}, keywords = {}, pubstate = {published}, tppubtype = {article} } In the fast growing field of multifrequency atomic force microscopy (AFM), the benefits of using higher-order modes has been extensively reported on. However, higher modes of AFM cantilevers are difficult to instrument and Q control is challenging owing to their high frequency nature. At these high frequencies, the latencies in the computations and analog conversions of digital signal processing platforms become significant and limit the effective bandwidth of digital feedback controller implementations. To address this issue, this article presents a novel cantilever design for which the first five modes are placed within a 200 kHz bandwidth. The proposed cantilever is designed using a structural optimization routine. The close spacing and low mechanical bandwidth of the resulting cantilever allows for the implementation of Q controllers for all five modes using a standard FPGA development board for bimodal AFM and imaging on higher-order modes. |
| 38. |  | D. M. Harcombe; M. G. Ruppert; A. J. Fleming A review of demodulation techniques for multifrequency atomic force microscopy Journal Article Beilstein Journal of Nanotechnology, 11 , pp. 76-97, 2020, ISSN: 21904286. @article{Harcombe2020, title = {A review of demodulation techniques for multifrequency atomic force microscopy}, author = {D. M. Harcombe and M. G. Ruppert and A. J. Fleming}, editor = {T. Glatzel}, url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2020/02/J20b-reducedSize.pdf}, doi = {doi:10.3762/bjnano.11.8}, issn = {21904286}, year = {2020}, date = {2020-01-07}, journal = {Beilstein Journal of Nanotechnology}, volume = {11}, pages = {76-97}, abstract = {This article compares the performance of traditional and recently proposed demodulators for multifrequency atomic force microscopy. The compared methods include the lock-in amplifier, coherent demodulator, Kalman filter, Lyapunov filter, and direct-design demodulator. Each method is implemented on a field-programmable gate array (FPGA) with a sampling rate of 1.5 MHz. The metrics for comparison include the sensitivity to other frequency components and the magnitude of demodulation artifacts for a range of demodulator bandwidths. Performance differences are demonstrated through higher harmonic atomic force microscopy imaging.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This article compares the performance of traditional and recently proposed demodulators for multifrequency atomic force microscopy. The compared methods include the lock-in amplifier, coherent demodulator, Kalman filter, Lyapunov filter, and direct-design demodulator. Each method is implemented on a field-programmable gate array (FPGA) with a sampling rate of 1.5 MHz. The metrics for comparison include the sensitivity to other frequency components and the magnitude of demodulation artifacts for a range of demodulator bandwidths. Performance differences are demonstrated through higher harmonic atomic force microscopy imaging. |
2019 |
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| 37. |  | M. G. Ruppert; N. F. S. D. Bem; A. J. Fleming; Y. K. Yong Characterization of Active Microcantilevers Using Laser Doppler Vibrometry Inproceedings 18th Asian Pacific Vibration Conference, Sydney, Australia, 2019. @inproceedings{Ruppert2019b, title = {Characterization of Active Microcantilevers Using Laser Doppler Vibrometry}, author = {M. G. Ruppert and N. F. S. D. Bem and A. J. Fleming and Y. K. Yong}, year = {2019}, date = {2019-11-18}, booktitle = {18th Asian Pacific Vibration Conference}, address = {Sydney, Australia}, abstract = {Active atomic force microscope cantilevers with on-chip actuation and sensing provide several advantages over passive cantilevers which rely on piezoacoustic base-excitation and the optical beam deflection measurement. Most importantly, these cantilevers provide clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interferences. In this paper, we demonstrate the analysis and calibration steps for three active cantilever geometries with integrated piezoelectric actuation. For this purpose, laser Doppler vibrometry (LDV) is used to experimentally obtain the deflection mode shapes of the first three eigenmodes, calibrate actuation gains, and to determine the dynamic modal stiffnesses using the Brownian spectrum of the cantilever. The experimental values are compared with finite element simulations.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Active atomic force microscope cantilevers with on-chip actuation and sensing provide several advantages over passive cantilevers which rely on piezoacoustic base-excitation and the optical beam deflection measurement. Most importantly, these cantilevers provide clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interferences. In this paper, we demonstrate the analysis and calibration steps for three active cantilever geometries with integrated piezoelectric actuation. For this purpose, laser Doppler vibrometry (LDV) is used to experimentally obtain the deflection mode shapes of the first three eigenmodes, calibrate actuation gains, and to determine the dynamic modal stiffnesses using the Brownian spectrum of the cantilever. The experimental values are compared with finite element simulations. |
| 36. |  | M. G. Ruppert; S. O. R. Moheimani Dynamics and Control of Active Microcantilevers Book Chapter Baillieul, John ; Samad, Tariq (Ed.): Encyclopedia of Systems and Control, 2 , Springer London, 2019, ISBN: 978-1-4471-5102-9. @inbook{Ruppert2019b, title = {Dynamics and Control of Active Microcantilevers}, author = {M. G. Ruppert and S. O. R. Moheimani}, editor = {Baillieul, John and Samad, Tariq}, url = {https://rd.springer.com/referenceworkentry/10.1007%2F978-1-4471-5102-9_184-2}, doi = {10.1007/978-1-4471-5102-9_184-2}, isbn = {978-1-4471-5102-9}, year = {2019}, date = {2019-11-16}, booktitle = {Encyclopedia of Systems and Control}, volume = {2}, publisher = {Springer London}, abstract = {The microcantilever is a key precision mechatronic component of many technologies for characterization and manipulation of matter at the nanoscale, particularly in the atomic force microscope. When a cantilever is operated in a regime that requires the direct excitation and measurement of its resonance frequencies, appropriate instrumentation and control is crucial for high-performance operation. In this entry, we discuss integrated cantilever actuation and present the cantilever transfer function model and its properties. As a result of using these active cantilevers, the ability to control the quality factor in order to manipulate the cantilever tracking bandwidth is demonstrated.}, keywords = {}, pubstate = {published}, tppubtype = {inbook} } The microcantilever is a key precision mechatronic component of many technologies for characterization and manipulation of matter at the nanoscale, particularly in the atomic force microscope. When a cantilever is operated in a regime that requires the direct excitation and measurement of its resonance frequencies, appropriate instrumentation and control is crucial for high-performance operation. In this entry, we discuss integrated cantilever actuation and present the cantilever transfer function model and its properties. As a result of using these active cantilevers, the ability to control the quality factor in order to manipulate the cantilever tracking bandwidth is demonstrated. |
| 35. |  | K. Wang; M. G. Ruppert; C. Manzie; D. Nesic; Y. K. Yong Scan Rate Adaptation for AFM Imaging Based on Performance Metric Optimisation Journal Article IEEE/ASME Transactions on Mechatronics, 2019, (early access). @article{Wang2019b, title = {Scan Rate Adaptation for AFM Imaging Based on Performance Metric Optimisation}, author = {K. Wang and M. G. Ruppert and C. Manzie and D. Nesic and Y. K. Yong }, url = {https://ieeexplore.ieee.org/document/8867937}, doi = {10.1109/TMECH.2019.2947203}, year = {2019}, date = {2019-10-14}, journal = { IEEE/ASME Transactions on Mechatronics}, abstract = {Constant-force contact-mode atomic force microscopy (AFM) relies on a feedback control system to regulate the tip-sample interaction during imaging. Due to limitations in actuators and control, the bandwidth of the regulation system is typically small. Therefore, the scan rate is usually limited in order to guarantee a desirable image quality for a constant-rate scan. By adapting the scan rate online, further performance improvement is possible, and the conditions to this improvement has been explored qualitatively in a previous study for a wide class of possible scan patterns. In this paper, a quantitative assessment of the previously proposed adaptive scan scheme is investigated through experiments that explore the impact of various degrees of freedom in the algorithm. Further modifications to the existing scheme are proposed and shown to improve the closed-loop performance. The flexibility of the proposed approach is further demonstrated by applying the algorithm to tapping-mode AFM.}, note = {early access}, keywords = {}, pubstate = {published}, tppubtype = {article} } Constant-force contact-mode atomic force microscopy (AFM) relies on a feedback control system to regulate the tip-sample interaction during imaging. Due to limitations in actuators and control, the bandwidth of the regulation system is typically small. Therefore, the scan rate is usually limited in order to guarantee a desirable image quality for a constant-rate scan. By adapting the scan rate online, further performance improvement is possible, and the conditions to this improvement has been explored qualitatively in a previous study for a wide class of possible scan patterns. In this paper, a quantitative assessment of the previously proposed adaptive scan scheme is investigated through experiments that explore the impact of various degrees of freedom in the algorithm. Further modifications to the existing scheme are proposed and shown to improve the closed-loop performance. The flexibility of the proposed approach is further demonstrated by applying the algorithm to tapping-mode AFM. |
| 34. |  | M. R. P. Ragazzon; S. Messineo; J. T. Gravdahl; D. M. Harcombe; M. G. Ruppert Generalized Lyapunov Demodulator for Amplitude and Phase Estimation by the Internal Model Principle Inproceedings 8th IFAC Symposium on Mechatronic Systems, 2019, (accepted for publication). @inproceedings{Ragazzon2019, title = {Generalized Lyapunov Demodulator for Amplitude and Phase Estimation by the Internal Model Principle}, author = {M. R. P. Ragazzon and S. Messineo and J. T. Gravdahl and D. M. Harcombe and M. G. Ruppert}, year = {2019}, date = {2019-09-04}, booktitle = {8th IFAC Symposium on Mechatronic Systems}, abstract = {Effective demodulation of amplitude and phase is a requirement in a wide array of applications. Recent efforts have increased the demodulation performance, in particular, the Lyapunov demodulator allows bandwidths up to the carrier frequency of the signal. However, being inherently restricted to a single order filtering of the input signal, signal components outside its passband are not sufficiently attenuated for all applications, such as in multifrequency atomic force microscopy. In this article, the structure of the Lyapunov demodulator is transformed to an equivalent form, taking advantage of the internal model representation of the sinusoid to be tracked. A generalization of this formulation allows the application of standard filtering techniques in order to shape the characteristics of the demodulator, while retaining the perfect tracking condition provided by the internal model. Guidelines for the filter design are provided in order to achieve the desired characteristics, such as filtering order, tracking bandwidth, and transient performance. The resulting generalized Lyapunov demodulator structure is highly flexible, allows for direct employment of any standard filter type, is computationally simple, and easy to implement requiring only a bandpass filter, a single integrator, and two nonlinear transformations. Numerical results demonstrate the effectiveness of the approach, and provide a comparison of the various filters considered.}, note = {accepted for publication}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Effective demodulation of amplitude and phase is a requirement in a wide array of applications. Recent efforts have increased the demodulation performance, in particular, the Lyapunov demodulator allows bandwidths up to the carrier frequency of the signal. However, being inherently restricted to a single order filtering of the input signal, signal components outside its passband are not sufficiently attenuated for all applications, such as in multifrequency atomic force microscopy. In this article, the structure of the Lyapunov demodulator is transformed to an equivalent form, taking advantage of the internal model representation of the sinusoid to be tracked. A generalization of this formulation allows the application of standard filtering techniques in order to shape the characteristics of the demodulator, while retaining the perfect tracking condition provided by the internal model. Guidelines for the filter design are provided in order to achieve the desired characteristics, such as filtering order, tracking bandwidth, and transient performance. The resulting generalized Lyapunov demodulator structure is highly flexible, allows for direct employment of any standard filter type, is computationally simple, and easy to implement requiring only a bandpass filter, a single integrator, and two nonlinear transformations. Numerical results demonstrate the effectiveness of the approach, and provide a comparison of the various filters considered. |
| 33. |  | L. McCourt; B. S. Routley; M. G. Ruppert; A. J. Fleming Resolution and Enhancement of Probes for Tip Enhanced Raman Spectroscopy Conference International Conference on Nanophotonics and Micro/Nano Optics (NANOP), Munich, Germany, 2019. @conference{McCourt2019, title = {Resolution and Enhancement of Probes for Tip Enhanced Raman Spectroscopy}, author = {L. McCourt and B. S. Routley and M. G. Ruppert and A. J. Fleming}, year = {2019}, date = {2019-09-04}, booktitle = {International Conference on Nanophotonics and Micro/Nano Optics (NANOP)}, journal = {International Conference Nanophotonics and Micro/Nano Optics}, address = {Munich, Germany}, abstract = {Two photon apertureless nearfield lithography allows sub diffraction limited features for integrated circuit production. It involves exciting surface plasmons on a metallic atomic force microscopy probe, which generates an enhancement of the localised electric field, exposing a photoresist. Costing less than extreme ultra violet lithography, and reducing exposure from scattered light compared to one photon nearfield lithography, this technique is suited for device prototyping or low volume production. The work here considers the material and geometry of an ideal AFM probe in terms of resolution (producing the smallest features) and electric field enhancement.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } Two photon apertureless nearfield lithography allows sub diffraction limited features for integrated circuit production. It involves exciting surface plasmons on a metallic atomic force microscopy probe, which generates an enhancement of the localised electric field, exposing a photoresist. Costing less than extreme ultra violet lithography, and reducing exposure from scattered light compared to one photon nearfield lithography, this technique is suited for device prototyping or low volume production. The work here considers the material and geometry of an ideal AFM probe in terms of resolution (producing the smallest features) and electric field enhancement. |
| 32. |  | S. I. Moore; M. G. Ruppert; Y. K. Yong An optimization framework for the design of piezoelectric AFM cantilevers Journal Article Precision Engineering, 60 , pp. 130-142, 2019. @article{Moore2019c, title = {An optimization framework for the design of piezoelectric AFM cantilevers}, author = {S. I. Moore and M. G. Ruppert and Y. K. Yong}, url = {https://www.sciencedirect.com/science/article/pii/S0141635919302260}, year = {2019}, date = {2019-08-15}, journal = {Precision Engineering}, volume = {60}, pages = {130-142}, abstract = {To facilitate further miniaturization of atomic force microscopy (AFM) cantilevers and to eliminate the standard optical beam deflection sensor, integrated piezoelectric actuation and sensing on the chip level is a promising option. This article presents a topology optimization method for dynamic mode AFM cantilevers that maximizes the sensitivity of an integrated piezoelectric sensor under stiffness and resonance frequency constraints. Included in the formulation is a new material model C-SIMP (connectivity and solid isotropic material with penalization) that extends the SIMP model to explicitly include the penalization of unconnected structures. Example cantilever designs demonstrate the potential of the topology optimization method. The results show, firstly, the C-SIMP material model significantly reduces connectivity issues and, secondly, arbitrary cantilever topologies can produce increases in sensor sensitivity or resonance frequency compared to a rectangular topology.}, keywords = {}, pubstate = {published}, tppubtype = {article} } To facilitate further miniaturization of atomic force microscopy (AFM) cantilevers and to eliminate the standard optical beam deflection sensor, integrated piezoelectric actuation and sensing on the chip level is a promising option. This article presents a topology optimization method for dynamic mode AFM cantilevers that maximizes the sensitivity of an integrated piezoelectric sensor under stiffness and resonance frequency constraints. Included in the formulation is a new material model C-SIMP (connectivity and solid isotropic material with penalization) that extends the SIMP model to explicitly include the penalization of unconnected structures. Example cantilever designs demonstrate the potential of the topology optimization method. The results show, firstly, the C-SIMP material model significantly reduces connectivity issues and, secondly, arbitrary cantilever topologies can produce increases in sensor sensitivity or resonance frequency compared to a rectangular topology. |
| 31. |  | S. I. Moore; M. G. Ruppert; D. M. Harcombe; A. J. Fleming; Y. K. Yong Design and Analysis of Low-Distortion Demodulators for Modulated Sensors Journal Article IEEE/ASME Transactions on Mechatronics, 24 (4), pp. 1861-1870, 2019, ISSN: 10834435. @article{Moore2019, title = {Design and Analysis of Low-Distortion Demodulators for Modulated Sensors}, author = { S. I. Moore and M. G. Ruppert and D. M. Harcombe and A. J. Fleming and Y. K. Yong }, url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2020/05/J19d-reduced.pdf}, doi = {10.1109/TMECH.2019.2928592}, issn = {10834435}, year = {2019}, date = {2019-07-17}, journal = {IEEE/ASME Transactions on Mechatronics}, volume = {24}, number = {4}, pages = {1861-1870}, abstract = {System-based demodulators in the form of a Kalman and Lyapunov filter have been demonstrated to significantly outperform traditional demodulators, such as the lock-in amplifier, in bandwidth sensitive applications, for example high-speed atomic force microscopy. Building on their closed loop architecture, this article describes a broader class of high-speed closed-loop demodulators. The generic structure provides greater flexibility to independently control the bandwidth and sensitivity to out-of-band frequencies. A linear time-invariant description is derived which allows the utilization of linear control theory to design the demodulator. Experimental results on a nanopositioner with capacitive sensors demonstrate the realization of arbitrary demodulator dynamics while achieving excellent noise rejection.}, keywords = {}, pubstate = {published}, tppubtype = {article} } System-based demodulators in the form of a Kalman and Lyapunov filter have been demonstrated to significantly outperform traditional demodulators, such as the lock-in amplifier, in bandwidth sensitive applications, for example high-speed atomic force microscopy. Building on their closed loop architecture, this article describes a broader class of high-speed closed-loop demodulators. The generic structure provides greater flexibility to independently control the bandwidth and sensitivity to out-of-band frequencies. A linear time-invariant description is derived which allows the utilization of linear control theory to design the demodulator. Experimental results on a nanopositioner with capacitive sensors demonstrate the realization of arbitrary demodulator dynamics while achieving excellent noise rejection. |
| 30. |  | D. M. Harcombe; M. G. Ruppert; A. J. Fleming Modeling and Noise Analysis of a Microcantilever-based Mass Sensor Inproceedings Int. Conference on Manipulation, Automation and Robotics at Small Scales (MARSS), Helsinki, Finland, 2019. @inproceedings{Harcombe2019, title = {Modeling and Noise Analysis of a Microcantilever-based Mass Sensor}, author = {D. M. Harcombe and M. G. Ruppert and A. J. Fleming}, year = {2019}, date = {2019-07-01}, booktitle = {Int. Conference on Manipulation, Automation and Robotics at Small Scales (MARSS)}, address = {Helsinki, Finland}, abstract = {Nanomechanical devices have the potential for practical applications as mass sensors. In microcantilever based sensing, resonance frequency shifts are tracked by a phase-locked loop (PLL) in-order to monitor mass adsorption. A major challenge in minimizing the mass detection limit comes from the noise present in the system due to thermal, sensor and oscillator noise. There is numerical difficulty in simulating PLLs, as both low frequency phase estimates and high frequency mixing products need to be captured resulting in a stiff problem. By using linear system-theoretic modeling an in-depth analysis of the system is able to be conducted overcoming this issue. This provides insight into individual noise source propagation, dominant noise sources and possible ways to reduce their effects. The developed model is verified in simulation against the non-linear PLL, with each achieving low picogram sensitivity for a 100 Hz loop bandwidth and realistically modeled noise sources.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Nanomechanical devices have the potential for practical applications as mass sensors. In microcantilever based sensing, resonance frequency shifts are tracked by a phase-locked loop (PLL) in-order to monitor mass adsorption. A major challenge in minimizing the mass detection limit comes from the noise present in the system due to thermal, sensor and oscillator noise. There is numerical difficulty in simulating PLLs, as both low frequency phase estimates and high frequency mixing products need to be captured resulting in a stiff problem. By using linear system-theoretic modeling an in-depth analysis of the system is able to be conducted overcoming this issue. This provides insight into individual noise source propagation, dominant noise sources and possible ways to reduce their effects. The developed model is verified in simulation against the non-linear PLL, with each achieving low picogram sensitivity for a 100 Hz loop bandwidth and realistically modeled noise sources. |
| 29. |  | M. G. Ruppert; B. S. Routley; A. J. Fleming; Y. K. Yong; G. E. Fantner Model-based Q Factor Control for Photothermally Excited Microcantilevers Inproceedings Int. Conference on Manipulation, Automation and Robotics at Small Scales (MARSS), Helsinki, Finland, 2019. @inproceedings{Ruppert2019, title = {Model-based Q Factor Control for Photothermally Excited Microcantilevers}, author = {M. G. Ruppert and B. S. Routley and A. J. Fleming and Y. K. Yong and G. E. Fantner}, year = {2019}, date = {2019-07-01}, booktitle = {Int. Conference on Manipulation, Automation and Robotics at Small Scales (MARSS)}, address = {Helsinki, Finland}, abstract = {Photothermal excitation of the cantilever for dynamic atomic force microscopy (AFM) modes is an attractive actuation method as it provides clean cantilever actuation leading to well-defined frequency responses. Unlike conventional piezo-acoustic excitation of the cantilever, it allows for model-based quality (Q) factor control in order to increase the cantilever tracking bandwidth for tapping-mode AFM or to reduce resonant ringing for high-speed photothermal offresonance tapping (PORT) in ambient conditions. In this work, we present system identification, controller design and experimental results on controlling the Q factor of a photothermally driven cantilever. The work is expected to lay the groundwork for future implementations for high-speed PORT imaging in ambient conditions.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Photothermal excitation of the cantilever for dynamic atomic force microscopy (AFM) modes is an attractive actuation method as it provides clean cantilever actuation leading to well-defined frequency responses. Unlike conventional piezo-acoustic excitation of the cantilever, it allows for model-based quality (Q) factor control in order to increase the cantilever tracking bandwidth for tapping-mode AFM or to reduce resonant ringing for high-speed photothermal offresonance tapping (PORT) in ambient conditions. In this work, we present system identification, controller design and experimental results on controlling the Q factor of a photothermally driven cantilever. The work is expected to lay the groundwork for future implementations for high-speed PORT imaging in ambient conditions. |
| 28. |  | K. Wang; M. G. Ruppert; C. Manzie; D. Nesic; Y. K. Yong Adaptive Scan for Atomic Force Microscopy Based on Online Optimisation: Theory and Experiment Journal Article IEEE Transactions on Control System Technology, 2019, (accepted for publication). @article{Wang2019, title = {Adaptive Scan for Atomic Force Microscopy Based on Online Optimisation: Theory and Experiment}, author = {K. Wang and M. G. Ruppert and C. Manzie and D. Nesic and Y. K. Yong}, url = {https://ieeexplore.ieee.org/document/8643730}, year = {2019}, date = {2019-01-31}, journal = {IEEE Transactions on Control System Technology}, abstract = {A major challenge in Atomic Force Microscopy (AFM) is to reduce the scan duration while retaining the image quality. Conventionally, the scan rate is restricted to a sufficiently small value in order to ensure a desirable image quality as well as a safe tip-sample contact force. This usually results in a conservative scan rate for samples that have a large variation in aspect ratio and/or for scan patterns that have a varying linear velocity. In this paper, an adaptive scan scheme is proposed to alleviate this problem. A scan line-based performance metric balancing both imaging speed and accuracy is proposed, and the scan rate is adapted such that the metric is optimised online in the presence of aspect ratio and/or linear velocity variations. The online optimisation is achieved using an extremum-seeking (ES) approach, and a semi-global practical asymptotic stability (SGPAS) result is shown for the overall system. Finally, the proposed scheme is demonstrated via both simulation and experiment.}, note = {accepted for publication}, keywords = {}, pubstate = {published}, tppubtype = {article} } A major challenge in Atomic Force Microscopy (AFM) is to reduce the scan duration while retaining the image quality. Conventionally, the scan rate is restricted to a sufficiently small value in order to ensure a desirable image quality as well as a safe tip-sample contact force. This usually results in a conservative scan rate for samples that have a large variation in aspect ratio and/or for scan patterns that have a varying linear velocity. In this paper, an adaptive scan scheme is proposed to alleviate this problem. A scan line-based performance metric balancing both imaging speed and accuracy is proposed, and the scan rate is adapted such that the metric is optimised online in the presence of aspect ratio and/or linear velocity variations. The online optimisation is achieved using an extremum-seeking (ES) approach, and a semi-global practical asymptotic stability (SGPAS) result is shown for the overall system. Finally, the proposed scheme is demonstrated via both simulation and experiment. |
| 27. |  | M. G. Ruppert; S. I. Moore; M. Zawierta; A. J. Fleming; G. Putrino; Y. K. Yong Multimodal atomic force microscopy with optimized higher eigenmode sensitivity using on-chip piezoelectric actuation and sensing Journal Article Nanotechnology, 30 (8), pp. 085503, 2019. @article{Ruppert2018b, title = {Multimodal atomic force microscopy with optimized higher eigenmode sensitivity using on-chip piezoelectric actuation and sensing}, author = {M. G. Ruppert and S. I. Moore and M. Zawierta and A. J. Fleming and G. Putrino and Y. K. Yong}, url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2019/08/Ruppert_2019_Nanotechnology_30_085503.pdf}, doi = {https://doi.org/10.1088/1361-6528/aae40b}, year = {2019}, date = {2019-01-02}, journal = {Nanotechnology}, volume = {30}, number = {8}, pages = {085503}, abstract = {Atomic force microscope (AFM) cantilevers with integrated actuation and sensing provide several distinct advantages over conventional cantilever instrumentation. These include clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interference. While cantilever microfabrication technology has continuously advanced over the years, the overall design has remained largely unchanged; a passive rectangular shaped cantilever design has been adopted as the industry wide standard. In this article, we demonstrate multimode AFM imaging on higher eigenmodes as well as bimodal AFM imaging with cantilevers using fully integrated piezoelectric actuation and sensing. The cantilever design maximizes the higher eigenmode deflection sensitivity by optimizing the transducer layout according to the strain mode shape. Without the need for feedthrough cancellation, the read-out method achieves close to zero actuator/sensor feedthrough and the sensitivity is sufficient to resolve the cantilever Brownian motion.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Atomic force microscope (AFM) cantilevers with integrated actuation and sensing provide several distinct advantages over conventional cantilever instrumentation. These include clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interference. While cantilever microfabrication technology has continuously advanced over the years, the overall design has remained largely unchanged; a passive rectangular shaped cantilever design has been adopted as the industry wide standard. In this article, we demonstrate multimode AFM imaging on higher eigenmodes as well as bimodal AFM imaging with cantilevers using fully integrated piezoelectric actuation and sensing. The cantilever design maximizes the higher eigenmode deflection sensitivity by optimizing the transducer layout according to the strain mode shape. Without the need for feedthrough cancellation, the read-out method achieves close to zero actuator/sensor feedthrough and the sensitivity is sufficient to resolve the cantilever Brownian motion. |
2018 |
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| 26. |  | M. G. Ruppert; Y. K. Yong Design of Hybrid Piezoelectric/Piezoresistive Cantilevers for Dynamic-mode Atomic Force Microscopy Inproceedings IEEE/ASME Advanced Intelligent Mechatronics (AIM), Auckland, New Zealand, 2018. @inproceedings{Ruppert2018b, title = {Design of Hybrid Piezoelectric/Piezoresistive Cantilevers for Dynamic-mode Atomic Force Microscopy}, author = {M. G. Ruppert and Y. K. Yong}, year = {2018}, date = {2018-07-09}, booktitle = {IEEE/ASME Advanced Intelligent Mechatronics (AIM)}, address = {Auckland, New Zealand}, abstract = {Atomic force microscope cantilevers with integrated actuation and sensing on the chip level provide several distinct advantages over conventional cantilever instrumentation. These include clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interferences. However, the two major difficulties with integrated transduction methods are a complicated fabrication process, often involving a number of fabrication steps, and a high amount of feedthrough from actuation to sensing electrodes. This work proposes two hybrid cantilever designs with piezoelectric actuators and piezoresistive sensors to reduce the actuator to sensor feedthrough. The designs can be realized using a commercial microelectromechanical systems fabrication process and only require a simple five-mask patterning and etching process. Finite element analysis results are presented to obtain modal responses, actuator gain and sensor sensitivities of the cantilever designs.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Atomic force microscope cantilevers with integrated actuation and sensing on the chip level provide several distinct advantages over conventional cantilever instrumentation. These include clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interferences. However, the two major difficulties with integrated transduction methods are a complicated fabrication process, often involving a number of fabrication steps, and a high amount of feedthrough from actuation to sensing electrodes. This work proposes two hybrid cantilever designs with piezoelectric actuators and piezoresistive sensors to reduce the actuator to sensor feedthrough. The designs can be realized using a commercial microelectromechanical systems fabrication process and only require a simple five-mask patterning and etching process. Finite element analysis results are presented to obtain modal responses, actuator gain and sensor sensitivities of the cantilever designs. |
| 25. |  | S. I. Moore; M. G. Ruppert; Y. K. Yong Arbitrary placement of AFM cantilever higher eigenmodes using structural optimization Inproceedings International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS), 2018. @inproceedings{Moore2018, title = {Arbitrary placement of AFM cantilever higher eigenmodes using structural optimization}, author = {S. I. Moore and M. G. Ruppert and Y. K. Yong}, year = {2018}, date = {2018-07-04}, booktitle = {International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS)}, journal = {International Conference on Manipulation, Automation and Robotics at Small Scales (MARSS)}, abstract = {This article presents a novel cantilever design approach to place higher mode frequencies within a specific frequency band to alleviate instrumentation and Q control feasibility. This work is motivated by the emerging field of multifrequency atomic force microscopy (AFM) which involves the excitation and/or detection of several cantilever modes at once. Unlike other operating modes, multifrequency AFM allows the tracking of the sample topography on the fundamental mode while simultaneously acquiring complimentary nanomechanical information on a higher mode. However, higher modes of conventional rectangular tapping-mode cantilevers are usually in the MHz regime and therefore impose severe restrictions on the direct controllability of these modes. To overcome this limitation, an optimization technique is employed which is capable of placing the first five modes within a 200 kHz bandwidth.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } This article presents a novel cantilever design approach to place higher mode frequencies within a specific frequency band to alleviate instrumentation and Q control feasibility. This work is motivated by the emerging field of multifrequency atomic force microscopy (AFM) which involves the excitation and/or detection of several cantilever modes at once. Unlike other operating modes, multifrequency AFM allows the tracking of the sample topography on the fundamental mode while simultaneously acquiring complimentary nanomechanical information on a higher mode. However, higher modes of conventional rectangular tapping-mode cantilevers are usually in the MHz regime and therefore impose severe restrictions on the direct controllability of these modes. To overcome this limitation, an optimization technique is employed which is capable of placing the first five modes within a 200 kHz bandwidth. |
| 24. |  | M. G. Ruppert; D. M. Harcombe; S. I. Moore; A. J. Fleming Direct Design of Closed-loop Demodulators for Amplitude Modulation Atomic Force Microscopy Inproceedings American Control Conference, Milwaukee, WI, 2018. @inproceedings{C18b, title = {Direct Design of Closed-loop Demodulators for Amplitude Modulation Atomic Force Microscopy}, author = {M. G. Ruppert and D. M. Harcombe and S. I. Moore and A. J. Fleming}, year = {2018}, date = {2018-06-27}, booktitle = {American Control Conference}, address = {Milwaukee, WI}, abstract = {A fundamental component of the z-axis feedback loop in amplitude modulation atomic force microscopy is the demodulator. It dictates both bandwidth and noise in the amplitude and phase estimate of the cantilever deflection signal. In this paper, we derive a linear time-invariant model of a closedloop demodulator with user definable tracking bandwidth and sensitivity to other frequency components. A direct demodulator design method is proposed based on the reformulation of the Lyapunov filter as a modulated-demodulated controller in closed loop with a unity plant. Simulation and experimental results for a higher order Lyapunov filter as well as Butterworth and Chebyshev type demodulators are presented.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } A fundamental component of the z-axis feedback loop in amplitude modulation atomic force microscopy is the demodulator. It dictates both bandwidth and noise in the amplitude and phase estimate of the cantilever deflection signal. In this paper, we derive a linear time-invariant model of a closedloop demodulator with user definable tracking bandwidth and sensitivity to other frequency components. A direct demodulator design method is proposed based on the reformulation of the Lyapunov filter as a modulated-demodulated controller in closed loop with a unity plant. Simulation and experimental results for a higher order Lyapunov filter as well as Butterworth and Chebyshev type demodulators are presented. |
| 23. |  | M. G. Ruppert Self-sensing, estimation and control in multifrequency Atomic Force Microscopy. Journal Article Journal & Proceedings of the Royal Society of New South Wales, 151 (1), pp. 111, 2018, ISSN: 0035-9173/18/010111-01. @article{Ruppert2018b, title = {Self-sensing, estimation and control in multifrequency Atomic Force Microscopy. }, author = {M. G. Ruppert}, url = {https://royalsoc.org.au/images/pdf/journal/151-1-Ruppert.pdf}, issn = {0035-9173/18/010111-01}, year = {2018}, date = {2018-06-01}, journal = {Journal & Proceedings of the Royal Society of New South Wales}, volume = {151}, number = {1}, pages = {111}, abstract = {Despite the undeniable success of the atomic force microscope (AFM), dynamic techniques still face limitations in terms of spatial resolution, imaging speed and high cost of acquisition. In order to expand the capabilities of the instrument, it was realized that the information about the nano-mechanical properties of a sample are encoded over a range of frequencies and the excitation and detection of higher-order eigenmodes of the micro-cantilever open up further informa- tion channels. The ability to control these modes and their fast responses to excitation is believed to be the key to unravelling the true potential of these ethods. This work addresses three major drawbacks of the standard AFM setup, which limit the feasibility of multi-frequency approaches. First, microelectromechanical system (MEMS) probes with integrated piezoelectric layers is motivated, enabling the development of novel multimode self-sensing and self-actuating techniques. Specifically, these piezoelectric transduction schemes permit the miniaturization of the entire AFM towards a cost-effective single-chip device with nanoscale precision in a much smaller form factor than that of conventional macroscale instruments. Second, the integrated actuation enables the development of multimode controllers which exhibits remarkable performance in arbitrarily modifying the quality factor of multiple eigenmodes and comes with inherent stability robustness. The experimental results demonstrate improved imaging stability, higher scan speeds and adjustable contrast when mapping nano-mechanical properties of soft samples. Last, in light of the demand for constantly increasing imaging speeds while providing multi-frequency flexibility, the estimation of multiple components of the high-frequency deflection signal is performed with a linear time-varying multi-frequency Kalman filter. The chosen representation allows for an efficient high-bandwidth implementation on a Field Programmable Gate Array. Tracking bandwidth, noise performance and trimodal AFM imaging on a two-component polymer sample are verified and shown to be superior to that of the commonly used lock-in amplifier.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Despite the undeniable success of the atomic force microscope (AFM), dynamic techniques still face limitations in terms of spatial resolution, imaging speed and high cost of acquisition. In order to expand the capabilities of the instrument, it was realized that the information about the nano-mechanical properties of a sample are encoded over a range of frequencies and the excitation and detection of higher-order eigenmodes of the micro-cantilever open up further informa- tion channels. The ability to control these modes and their fast responses to excitation is believed to be the key to unravelling the true potential of these ethods. This work addresses three major drawbacks of the standard AFM setup, which limit the feasibility of multi-frequency approaches. First, microelectromechanical system (MEMS) probes with integrated piezoelectric layers is motivated, enabling the development of novel multimode self-sensing and self-actuating techniques. Specifically, these piezoelectric transduction schemes permit the miniaturization of the entire AFM towards a cost-effective single-chip device with nanoscale precision in a much smaller form factor than that of conventional macroscale instruments. Second, the integrated actuation enables the development of multimode controllers which exhibits remarkable performance in arbitrarily modifying the quality factor of multiple eigenmodes and comes with inherent stability robustness. The experimental results demonstrate improved imaging stability, higher scan speeds and adjustable contrast when mapping nano-mechanical properties of soft samples. Last, in light of the demand for constantly increasing imaging speeds while providing multi-frequency flexibility, the estimation of multiple components of the high-frequency deflection signal is performed with a linear time-varying multi-frequency Kalman filter. The chosen representation allows for an efficient high-bandwidth implementation on a Field Programmable Gate Array. Tracking bandwidth, noise performance and trimodal AFM imaging on a two-component polymer sample are verified and shown to be superior to that of the commonly used lock-in amplifier. |
| 22. |  | M. G. Ruppert; S. I. Moore; M. Zawierta; G. Putrino; Y. K. Yong Advanced Sensing and Control with Active Cantilevers for Multimodal Atomic Force Microscopy Conference 7th Multifrequency AFM Conference, Madrid, Spain, 2018. @conference{Ruppert2018, title = {Advanced Sensing and Control with Active Cantilevers for Multimodal Atomic Force Microscopy}, author = {M. G. Ruppert and S. I. Moore and M. Zawierta and G. Putrino and Y. K. Yong}, year = {2018}, date = {2018-04-18}, booktitle = {7th Multifrequency AFM Conference}, address = {Madrid, Spain}, abstract = {Atomic force microscopy (AFM) cantilevers with integrated actuation and sensing on the chip level provide several distinct advantages over conventional cantilever instrumentation. These include clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interferences. While cantilever microfabrication technology has continuously advanced over the years, the overall design has remained largely unchanged; a passive rectangular shaped cantilever design has been adopted as the industry wide standard. Consequently, conventional cantilever instrumentation requires external piezo acoustic excitation as well as an external optical deflection sensor. Both of these components are not optimal for current trends in multifrequency AFM technology which revolve around further down-sizing, parallelization and measurements at multiple higher eigenmodes. Using microelectromechanical systems (MEMS) fabrication processes, this work aims to optimize cantilever instrumentation by realizing a new class of probes with high-performance integrated actuators and sensors. Equipped with multiple integrated piezoelectric layers for both actuation and sensing, these cantilevers are capable of achieving an increased higher eigenmode sensitivity and/or guaranteed collocated system properties compared to commercially available counterparts; examples of such designs are shown in Figure 1. The geometry as well as the integrated actuator/sensor arrangement is optimized using finite element modelling with individual design goals. The designs are realized using a commercial MEMS fabrication process and only require a simple five-mask patterning and etching process and post-fabricated sharp tips.}, keywords = {}, pubstate = {published}, tppubtype = {conference} } Atomic force microscopy (AFM) cantilevers with integrated actuation and sensing on the chip level provide several distinct advantages over conventional cantilever instrumentation. These include clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interferences. While cantilever microfabrication technology has continuously advanced over the years, the overall design has remained largely unchanged; a passive rectangular shaped cantilever design has been adopted as the industry wide standard. Consequently, conventional cantilever instrumentation requires external piezo acoustic excitation as well as an external optical deflection sensor. Both of these components are not optimal for current trends in multifrequency AFM technology which revolve around further down-sizing, parallelization and measurements at multiple higher eigenmodes. Using microelectromechanical systems (MEMS) fabrication processes, this work aims to optimize cantilever instrumentation by realizing a new class of probes with high-performance integrated actuators and sensors. Equipped with multiple integrated piezoelectric layers for both actuation and sensing, these cantilevers are capable of achieving an increased higher eigenmode sensitivity and/or guaranteed collocated system properties compared to commercially available counterparts; examples of such designs are shown in Figure 1. The geometry as well as the integrated actuator/sensor arrangement is optimized using finite element modelling with individual design goals. The designs are realized using a commercial MEMS fabrication process and only require a simple five-mask patterning and etching process and post-fabricated sharp tips. |
| 21. |  | D. M. Harcombe; M. G. Ruppert; M. R. P. Ragazzon; A. J. Fleming Lyapunov Estimation for High-Speed Demodulation in Multifrequency Atomic Force Microscopy Journal Article Beilstein Journal of Nanotechnology, 9 , pp. 490-498, 2018, ISSN: 21904286. @article{J18c, title = {Lyapunov Estimation for High-Speed Demodulation in Multifrequency Atomic Force Microscopy}, author = {D. M. Harcombe and M. G. Ruppert and M. R. P. Ragazzon and A. J. Fleming}, url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2018/02/J18c.pdf}, doi = {10.3762/bjnano.9.47}, issn = {21904286}, year = {2018}, date = {2018-02-28}, journal = {Beilstein Journal of Nanotechnology}, volume = {9}, pages = {490-498}, abstract = {An important issue in the emerging field of multifrequency atomic force microscopy (MF-AFM) is the accurate and fast demodulation of the cantilever-tip deflection signal. As this signal consists of multiple frequency components and noise processes, a lock-in amplifier is typically employed for its narrowband response. However, this demodulator suffers inherent bandwidth limitations as high frequency mixing products must be filtered out and several must be operated in parallel. Many MF-AFM methods require amplitude and phase demodulation at multiple frequencies of interest, enabling both z-axis feedback and phase contrast imaging to be achieved. This article proposes a model-based multifrequency Lyapunov filter implemented on a Field Programmable Gate Array (FPGA) for high-speed MF-AFM demodulation. System descriptions and simulations are verified by experimental results demonstrating high tracking bandwidths, strong off-mode rejection and minor sensitivity to cross-coupling effects. Additionally, a five-frequency system operating at 3.5MHz is implemented for higher harmonic amplitude and phase imaging up to 1MHz.}, keywords = {}, pubstate = {published}, tppubtype = {article} } An important issue in the emerging field of multifrequency atomic force microscopy (MF-AFM) is the accurate and fast demodulation of the cantilever-tip deflection signal. As this signal consists of multiple frequency components and noise processes, a lock-in amplifier is typically employed for its narrowband response. However, this demodulator suffers inherent bandwidth limitations as high frequency mixing products must be filtered out and several must be operated in parallel. Many MF-AFM methods require amplitude and phase demodulation at multiple frequencies of interest, enabling both z-axis feedback and phase contrast imaging to be achieved. This article proposes a model-based multifrequency Lyapunov filter implemented on a Field Programmable Gate Array (FPGA) for high-speed MF-AFM demodulation. System descriptions and simulations are verified by experimental results demonstrating high tracking bandwidths, strong off-mode rejection and minor sensitivity to cross-coupling effects. Additionally, a five-frequency system operating at 3.5MHz is implemented for higher harmonic amplitude and phase imaging up to 1MHz. |
2017 |
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| 20. |  | M. G. Ruppert; D. M. Harcombe; M. R. P. Ragazzon; S. O. R. Moheimani; A. J. Fleming A Review of Demodulation Techniques for Amplitude Modulation Atomic Force Microscopy Journal Article Bellstein Journal of Nanotechnology, 8 , pp. 1407–1426, 2017. @article{J17h, title = {A Review of Demodulation Techniques for Amplitude Modulation Atomic Force Microscopy}, author = {M. G. Ruppert and D. M. Harcombe and M. R. P. Ragazzon and S. O. R. Moheimani and A. J. Fleming}, url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2020/08/2190-4286-8-142.pdf}, doi = {10.3762/bjnano.8.142}, year = {2017}, date = {2017-09-01}, journal = {Bellstein Journal of Nanotechnology}, volume = {8}, pages = {1407–1426}, abstract = {In this review paper, traditional and novel demodulation methods applicable to amplitude modulation atomic force microscopy are implemented on a widely used digital processing system. As a crucial bandwidth-limiting component in the z-axis feedback loop of an atomic force microscope, the purpose of the demodulator is to obtain estimates of amplitude and phase of the cantilever deflection signal in the presence of sensor noise or additional distinct frequency components. Specifically for modern multifrequency techniques, where higher harmonic and/or higher eigenmode contributions are present in the oscillation signal, the fidelity of the estimates obtained from some demodulation techniques is not guaranteed. To enable a rigorous comparison, the performance metrics tracking bandwidth, implementation complexity and sensitivity to other frequency components are experimentally evaluated for each method. Finally, the significance of an adequate demodulator bandwidth is highlighted during high-speed tapping-mode AFM experiments in constant height mode.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In this review paper, traditional and novel demodulation methods applicable to amplitude modulation atomic force microscopy are implemented on a widely used digital processing system. As a crucial bandwidth-limiting component in the z-axis feedback loop of an atomic force microscope, the purpose of the demodulator is to obtain estimates of amplitude and phase of the cantilever deflection signal in the presence of sensor noise or additional distinct frequency components. Specifically for modern multifrequency techniques, where higher harmonic and/or higher eigenmode contributions are present in the oscillation signal, the fidelity of the estimates obtained from some demodulation techniques is not guaranteed. To enable a rigorous comparison, the performance metrics tracking bandwidth, implementation complexity and sensitivity to other frequency components are experimentally evaluated for each method. Finally, the significance of an adequate demodulator bandwidth is highlighted during high-speed tapping-mode AFM experiments in constant height mode. |
| 19. |  | M. G. Ruppert; Y. K. Yong Note: Guaranteed collocated multimode control of an atomic force microscope cantilever using on-chip piezoelectric actuation and sensing Journal Article Review of Scientific Instruments, 88 (086109), 2017. @article{Ruppert2017b, title = {Note: Guaranteed collocated multimode control of an atomic force microscope cantilever using on-chip piezoelectric actuation and sensing}, author = {M. G. Ruppert and Y. K. Yong}, url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2017/08/2017_JNote_RSI_Vol88_086109-2.pdf}, doi = {10.1063/1.4990451}, year = {2017}, date = {2017-08-15}, journal = {Review of Scientific Instruments}, volume = {88}, number = {086109}, abstract = {The quality (Q) factor is an important parameter of the resonance of the microcantilever as it determines both imaging bandwidth and force sensitivity. The ability to control the Q factor of multiple modes is believed to be of great benefit for atomic force microscopy techniques involving multiple eigenmodes. In this paper, we propose a novel cantilever design employing multiple piezoelectric transducers which are used for separated actuation and sensing, leading to guaranteed collocation of the first eight eigenmodes up to 3 MHz. The design minimizes the feedthrough usually observed with these systems by incorporating a guard trace on the cantilever chip. As a result, a multimode Q controller is demonstrated to be able to modify the quality factor of the first two eigenmodes over up to four orders of magnitude without sacrificing robust stability.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The quality (Q) factor is an important parameter of the resonance of the microcantilever as it determines both imaging bandwidth and force sensitivity. The ability to control the Q factor of multiple modes is believed to be of great benefit for atomic force microscopy techniques involving multiple eigenmodes. In this paper, we propose a novel cantilever design employing multiple piezoelectric transducers which are used for separated actuation and sensing, leading to guaranteed collocation of the first eight eigenmodes up to 3 MHz. The design minimizes the feedthrough usually observed with these systems by incorporating a guard trace on the cantilever chip. As a result, a multimode Q controller is demonstrated to be able to modify the quality factor of the first two eigenmodes over up to four orders of magnitude without sacrificing robust stability. |
| 18. |  | M. R. P. Ragazzon; M. G. Ruppert; D. M. Harcombe; A. J. Fleming; J. T. Gravdahl Lyapunov Estimator for High-Speed Demodulation in Dynamic Mode Atomic Force Microscopy Journal Article IEEE Transactions on Control Systems Technology, 26 (2), pp. 765-772, 2017. @article{J17e, title = {Lyapunov Estimator for High-Speed Demodulation in Dynamic Mode Atomic Force Microscopy}, author = {M. R. P. Ragazzon and M. G. Ruppert and D. M. Harcombe and A. J. Fleming and J. T. Gravdahl}, url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2017/09/J17e.pdf}, year = {2017}, date = {2017-08-01}, journal = {IEEE Transactions on Control Systems Technology}, volume = {26}, number = {2}, pages = {765-772}, abstract = {In dynamic mode atomic force microscopy (AFM), the imaging bandwidth is governed by the slowest component in the open-loop chain consisting of the vertical actuator, cantilever and demodulator. While the common demodulation method is to use a lock-in amplifier (LIA), its performance is ultimately bounded by the bandwidth of the post-mixing low-pass filters. This article proposes an amplitude and phase estimation method based on a strictly positive real Lyapunov design approach. The estimator is designed to be of low complexity while allowing for high bandwidth. Additionally, suitable gains for high performance are suggested such that no tuning is necessary. The Lyapunov estimator is experimentally implemented for amplitude demodulation and shown to surpass the LIA in terms of tracking bandwidth and noise performance. High-speed AFM images are presented to corroborate the results.}, keywords = {}, pubstate = {published}, tppubtype = {article} } In dynamic mode atomic force microscopy (AFM), the imaging bandwidth is governed by the slowest component in the open-loop chain consisting of the vertical actuator, cantilever and demodulator. While the common demodulation method is to use a lock-in amplifier (LIA), its performance is ultimately bounded by the bandwidth of the post-mixing low-pass filters. This article proposes an amplitude and phase estimation method based on a strictly positive real Lyapunov design approach. The estimator is designed to be of low complexity while allowing for high bandwidth. Additionally, suitable gains for high performance are suggested such that no tuning is necessary. The Lyapunov estimator is experimentally implemented for amplitude demodulation and shown to surpass the LIA in terms of tracking bandwidth and noise performance. High-speed AFM images are presented to corroborate the results. |
| 17. |  | D. M. Harcombe; M. G. Ruppert; A. J. Fleming Higher-harmonic AFM Imaging with a High-Bandwidth Multifrequency Lyapunov Filter Inproceedings IEEE/ASME Advanced Intelligent Mechatronics (AIM), Munich, Germany, 2017. @inproceedings{C17e, title = {Higher-harmonic AFM Imaging with a High-Bandwidth Multifrequency Lyapunov Filter}, author = {D. M. Harcombe and M. G. Ruppert and A. J. Fleming}, year = {2017}, date = {2017-07-03}, booktitle = {IEEE/ASME Advanced Intelligent Mechatronics (AIM)}, address = {Munich, Germany}, abstract = {A major difficulty in multifrequency atomic force microscopy (MF-AFM) is the accurate estimation of amplitude and phase at multiple frequencies for both z-axis feedback and material contrast imaging. Typically a lock-in amplifier is chosen as it is both narrowband and simple to implement. However, it inherently suffers drawbacks including a limited bandwidth due to post mixing low-pass filters and the necessity for multiple to be operated in parallel for MF-AFM. This paper proposes a multifrequency demodulator in the form of a modelbased Lyapunov filter implemented on a Field Programmable Gate Array (FPGA). System modelling and simulations are verified by experimental results demonstrating high tracking bandwidth and off-mode rejection at modelled frequencies. Additionally, AFM scans with a five-frequency-based system are presented wherein higher harmonic imaging is performed up to 1 MHz.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } A major difficulty in multifrequency atomic force microscopy (MF-AFM) is the accurate estimation of amplitude and phase at multiple frequencies for both z-axis feedback and material contrast imaging. Typically a lock-in amplifier is chosen as it is both narrowband and simple to implement. However, it inherently suffers drawbacks including a limited bandwidth due to post mixing low-pass filters and the necessity for multiple to be operated in parallel for MF-AFM. This paper proposes a multifrequency demodulator in the form of a modelbased Lyapunov filter implemented on a Field Programmable Gate Array (FPGA). System modelling and simulations are verified by experimental results demonstrating high tracking bandwidth and off-mode rejection at modelled frequencies. Additionally, AFM scans with a five-frequency-based system are presented wherein higher harmonic imaging is performed up to 1 MHz. |
| 16. |  | S. I. Moore; M. G. Ruppert; Y. K. Yong Design and Analysis of Piezoelectric Cantilevers with Enhanced Higher Eigenmodes for Atomic Force Microscopy Inproceedings IEEE/ASME Advanced Intelligent Mechatronics (AIM), Munich, Germany, 2017. @inproceedings{Moore2017b, title = {Design and Analysis of Piezoelectric Cantilevers with Enhanced Higher Eigenmodes for Atomic Force Microscopy}, author = {S. I. Moore and M. G. Ruppert and Y. K. Yong}, year = {2017}, date = {2017-07-02}, booktitle = {IEEE/ASME Advanced Intelligent Mechatronics (AIM)}, address = {Munich, Germany}, abstract = {Atomic force microscope (AFM) cantilevers with integrated actuation and sensing provide several distinct advantages over conventional cantilever instrumentation such as clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interferences. However, for multifrequency AFM techniques involving higher eigenmodes of the cantilever, optimization of the transducer location and layout has to be taken into account. This work proposes multiple integrated piezoelectric regions on the cantilever which maximize the deflection of the cantilever and the piezoelectric charge response for a given higher eigenmode based on the spatial strain distribution. Finite element analysis is performed to find the optimal transducer topology and experimental results are presented which highlight an actuation gain improvement up to 42 dB on the third mode and sensor sensitivity improvement up to 38 dB on the second mode.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Atomic force microscope (AFM) cantilevers with integrated actuation and sensing provide several distinct advantages over conventional cantilever instrumentation such as clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interferences. However, for multifrequency AFM techniques involving higher eigenmodes of the cantilever, optimization of the transducer location and layout has to be taken into account. This work proposes multiple integrated piezoelectric regions on the cantilever which maximize the deflection of the cantilever and the piezoelectric charge response for a given higher eigenmode based on the spatial strain distribution. Finite element analysis is performed to find the optimal transducer topology and experimental results are presented which highlight an actuation gain improvement up to 42 dB on the third mode and sensor sensitivity improvement up to 38 dB on the second mode. |
| 15. |  | M. G. Ruppert; M. Maroufi; A. Bazaei; S. O. R. Moheimani Kalman Filter Enabled High-Speed Control of a MEMS Nanopositioner Inproceedings 20th IFAC World Congress, pp. 15554-15560, 2017. @inproceedings{Ruppert2017b, title = {Kalman Filter Enabled High-Speed Control of a MEMS Nanopositioner}, author = {M. G. Ruppert and M. Maroufi and A. Bazaei and S. O. R. Moheimani}, year = {2017}, date = {2017-07-01}, booktitle = {20th IFAC World Congress}, volume = {50}, number = {1}, pages = {15554-15560}, abstract = {We demonstrate a novel tracking controller formulation based on a linear time-varying Kalman Filter to regulate amplitude and phase of a reference signal independently. The method is applicable to sinusoidal references such as spiral, cycloid and Lissajous trajectories which are commonly used for imaging in high-speed Atomic Force Microscopy (AFM). A Microelectromechanical Systems (MEMS) based nanopositioner, whose fundamental resonance frequency is dampened with an additional damping feedback loop, is employed. For a scan range of 2um, we demonstrate experimental tracking of sinusoids with frequencies as high as 5kHz, well beyond the open-loop fundamental resonance, with a tracking error of only 4.6nm.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } We demonstrate a novel tracking controller formulation based on a linear time-varying Kalman Filter to regulate amplitude and phase of a reference signal independently. The method is applicable to sinusoidal references such as spiral, cycloid and Lissajous trajectories which are commonly used for imaging in high-speed Atomic Force Microscopy (AFM). A Microelectromechanical Systems (MEMS) based nanopositioner, whose fundamental resonance frequency is dampened with an additional damping feedback loop, is employed. For a scan range of 2um, we demonstrate experimental tracking of sinusoids with frequencies as high as 5kHz, well beyond the open-loop fundamental resonance, with a tracking error of only 4.6nm. |
| 14. |  | M. G. Ruppert; D. M. Harcombe; M. R. P. Ragazzon; S. O. R. Moheimani; A. J. Fleming Frequency Domain Analysis of Robust Demodulators for High-Speed Atomic Force Microscopy Inproceedings American Control Conference, Seattle, WA, 2017. @inproceedings{C17b, title = {Frequency Domain Analysis of Robust Demodulators for High-Speed Atomic Force Microscopy}, author = {M. G. Ruppert and D. M. Harcombe and M. R. P. Ragazzon and S. O. R. Moheimani and A. J. Fleming}, year = {2017}, date = {2017-05-01}, booktitle = {American Control Conference}, address = {Seattle, WA}, abstract = {A fundamental but often overlooked component in the z-axis feedback loop of the atomic force microscope (AFM) operated in dynamic mode is the demodulator. It’s purpose is to obtain a preferably fast and low-noise estimate of amplitude and phase of the cantilever deflection signal in the presence of sensor noise and additional distinct frequency components. In this paper, we implement both traditional and recently developed robust methods on a labVIEW digital processing system and rigorously compare these techniques experimentally in terms of measurement bandwidth, implementation complexity and robustness to noise. We conclude with showing high-speed tapping-mode AFM images in constant height, highlighting the significance of an adequate demodulator bandwidth.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } A fundamental but often overlooked component in the z-axis feedback loop of the atomic force microscope (AFM) operated in dynamic mode is the demodulator. It’s purpose is to obtain a preferably fast and low-noise estimate of amplitude and phase of the cantilever deflection signal in the presence of sensor noise and additional distinct frequency components. In this paper, we implement both traditional and recently developed robust methods on a labVIEW digital processing system and rigorously compare these techniques experimentally in terms of measurement bandwidth, implementation complexity and robustness to noise. We conclude with showing high-speed tapping-mode AFM images in constant height, highlighting the significance of an adequate demodulator bandwidth. |
| 13. |  | M. Maroufi; M. G. Ruppert; A. G. Fowler; S. O. R. Moheimani Design and Control of a Single-chip SOI-MEMS Atomic Force Microscope Inproceedings American Control Conference, 2017. @inproceedings{Maroufi2017, title = {Design and Control of a Single-chip SOI-MEMS Atomic Force Microscope}, author = {M. Maroufi and M. G. Ruppert and A. G. Fowler and S. O. R. Moheimani}, year = {2017}, date = {2017-05-01}, booktitle = {American Control Conference}, abstract = {This paper presents a novel microelectromechanical systems (MEMS) implementation of an on-chip atomic force microscope (AFM), fabricated using a silicon-on-insulator process. The device features an XY scanner with electrostatic actuators and electrothermal sensors, as well as an integrated silicon microcantilever. A single AlN piezoelectric electrode is used for simultaneous actuation and deflection sensing of the cantilever via a charge sensing technique. With the device being operated in closed loop, the probe scanner is successfully used to obtain 8mmx8mm tapping-mode AFM images of a calibration grating.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } This paper presents a novel microelectromechanical systems (MEMS) implementation of an on-chip atomic force microscope (AFM), fabricated using a silicon-on-insulator process. The device features an XY scanner with electrostatic actuators and electrothermal sensors, as well as an integrated silicon microcantilever. A single AlN piezoelectric electrode is used for simultaneous actuation and deflection sensing of the cantilever via a charge sensing technique. With the device being operated in closed loop, the probe scanner is successfully used to obtain 8mmx8mm tapping-mode AFM images of a calibration grating. |
| 12. |  | S. I. Moore; M. G. Ruppert; Y. K. Yong Multimodal cantilevers with novel piezoelectric layer topology for sensitivity enhancement Journal Article Beilstein Journal of Nanotechnology, 8 , pp. 358–371, 2017. @article{Moore2017b, title = {Multimodal cantilevers with novel piezoelectric layer topology for sensitivity enhancement}, author = {S. I. Moore and M. G. Ruppert and Y. K. Yong}, url = {http://www.precisionmechatronicslab.com/wp-content/uploads/2017/02/2190-4286-8-38.pdf}, year = {2017}, date = {2017-02-06}, journal = {Beilstein Journal of Nanotechnology}, volume = {8}, pages = {358--371}, abstract = {Self-sensing techniques for atomic force microscope (AFM) cantilevers have several advantageous characteristics compared to the optical beam deflection method. The possibility of down scaling, parallelization of cantilever arrays and the absence of optical interference associated imaging artifacts have led to an increased research interest in these methods. However, for multifrequency AFM, the optimization of the transducer layout on the cantilever for higher order modes has not been addressed. To fully utilize an integrated piezoelectric transducer, this work alters the layout of the piezoelectric layer to maximize both the deflection of the cantilever and measured piezoelectric charge response for a given mode with respect to the spatial distribution of the strain. On a prototype cantilever design, significant increases in actuator and sensor sensitivities were achieved for the first four modes without any substantial increase in sensor noise. The transduction mechanism is specifically targeted at multifrequency AFM and has the potential to provide higher resolution imaging on higher order modes.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Self-sensing techniques for atomic force microscope (AFM) cantilevers have several advantageous characteristics compared to the optical beam deflection method. The possibility of down scaling, parallelization of cantilever arrays and the absence of optical interference associated imaging artifacts have led to an increased research interest in these methods. However, for multifrequency AFM, the optimization of the transducer layout on the cantilever for higher order modes has not been addressed. To fully utilize an integrated piezoelectric transducer, this work alters the layout of the piezoelectric layer to maximize both the deflection of the cantilever and measured piezoelectric charge response for a given mode with respect to the spatial distribution of the strain. On a prototype cantilever design, significant increases in actuator and sensor sensitivities were achieved for the first four modes without any substantial increase in sensor noise. The transduction mechanism is specifically targeted at multifrequency AFM and has the potential to provide higher resolution imaging on higher order modes. |
| 11. |  | M. G. Ruppert; A. G. Fowler; M. Maroufi; S. O. R. Moheimani On-chip Dynamic Mode Atomic Force Microscopy: A silicon-on-insulator MEMS approach Journal Article IEEE Journal of Microelectromechanical Systems, 26 (1), pp. 215-225, 2017. @article{Ruppert2017, title = {On-chip Dynamic Mode Atomic Force Microscopy: A silicon-on-insulator MEMS approach}, author = {M. G. Ruppert and A. G. Fowler and M. Maroufi and S. O. R. Moheimani}, doi = {10.1109/JMEMS.2016.2628890}, year = {2017}, date = {2017-02-01}, journal = {IEEE Journal of Microelectromechanical Systems}, volume = {26}, number = {1}, pages = {215-225}, abstract = {The atomic force microscope (AFM) is an invaluable scientific tool; however, its conventional implementation as a relatively costly macroscale system is a barrier to its more widespread use. A microelectromechanical systems (MEMS) approach to AFM design has the potential to significantly reduce the cost and complexity of the AFM, expanding its utility beyond current applications. This paper presents an on-chip AFM based on a silicon-on-insulator MEMS fabrication process. The device features integrated xy electrostatic actuators and electrothermal sensors as well as an AlN piezoelectric layer for out-of-plane actuation and integrated deflection sensing of a microcantilever. The three-degree-of-freedom design allows the probe scanner to obtain topographic tapping-mode AFM images with an imaging range of up to 8μm x 8μm in closed loop.}, keywords = {}, pubstate = {published}, tppubtype = {article} } The atomic force microscope (AFM) is an invaluable scientific tool; however, its conventional implementation as a relatively costly macroscale system is a barrier to its more widespread use. A microelectromechanical systems (MEMS) approach to AFM design has the potential to significantly reduce the cost and complexity of the AFM, expanding its utility beyond current applications. This paper presents an on-chip AFM based on a silicon-on-insulator MEMS fabrication process. The device features integrated xy electrostatic actuators and electrothermal sensors as well as an AlN piezoelectric layer for out-of-plane actuation and integrated deflection sensing of a microcantilever. The three-degree-of-freedom design allows the probe scanner to obtain topographic tapping-mode AFM images with an imaging range of up to 8μm x 8μm in closed loop. |
2016 |
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| 10. |  | M. G. Ruppert; D. M. Harcombe; S. O. R. Moheimani High-Bandwidth Demodulation in MF-AFM: A Kalman Filtering Approach Journal Article IEEE/ASME Transactions on Mechatronics, 21 (6), pp. 2705-2715, 2016. @article{Ruppert2016, title = {High-Bandwidth Demodulation in MF-AFM: A Kalman Filtering Approach}, author = {M. G. Ruppert and D. M. Harcombe and S. O. R. Moheimani}, doi = {10.1109/TMECH.2016.2574640}, year = {2016}, date = {2016-12-01}, journal = {IEEE/ASME Transactions on Mechatronics}, volume = {21}, number = {6}, pages = {2705-2715}, abstract = {Emerging multifrequency atomic force microscopy (MF-AFM) methods rely on coherent demodulation of the cantilever deflection signal at multiple frequencies. These measurements are needed in order to close the z-axis feedback loop and to acquire complementary information on the tip-sample interaction. While the common method is to use a lock-in amplifier capable of recovering low-level signals from noisy backgrounds, its performance is ultimately bounded by the bandwidth of the low-pass filters. In light of the demand for constantly increasing imaging speeds while providing multifrequency flexibility, we propose to estimate the in-phase and quadrature components with a linear time-varying Kalman filter. The chosen representation allows for an efficient high-bandwidth implementation on a Field Programmable Gate Array (FPGA). Tracking bandwidth and noise performance are verified experimentally and trimodal AFM results on a two-component polymer sample highlight the applicability of the proposed method for MF-AFM.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Emerging multifrequency atomic force microscopy (MF-AFM) methods rely on coherent demodulation of the cantilever deflection signal at multiple frequencies. These measurements are needed in order to close the z-axis feedback loop and to acquire complementary information on the tip-sample interaction. While the common method is to use a lock-in amplifier capable of recovering low-level signals from noisy backgrounds, its performance is ultimately bounded by the bandwidth of the low-pass filters. In light of the demand for constantly increasing imaging speeds while providing multifrequency flexibility, we propose to estimate the in-phase and quadrature components with a linear time-varying Kalman filter. The chosen representation allows for an efficient high-bandwidth implementation on a Field Programmable Gate Array (FPGA). Tracking bandwidth and noise performance are verified experimentally and trimodal AFM results on a two-component polymer sample highlight the applicability of the proposed method for MF-AFM. |
| 9. |  | M. G. Ruppert; S. O. R. Moheimani Multimode Q Control in Tapping-Mode AFM: Enabling Imaging on Higher Flexural Eigenmodes Journal Article IEEE Transactions on Control Systems Technology, 24 (4), pp. 1149-1159, 2016. @article{Ruppert2016b, title = {Multimode Q Control in Tapping-Mode AFM: Enabling Imaging on Higher Flexural Eigenmodes}, author = {M. G. Ruppert and S. O. R. Moheimani}, doi = {10.1109/TCST.2015.2478077}, year = {2016}, date = {2016-07-01}, journal = {IEEE Transactions on Control Systems Technology}, volume = {24}, number = {4}, pages = {1149-1159}, abstract = {Numerous dynamic Atomic Force Microscopy (AFM) methods have appeared in recent years, which make use of the excitation and detection of higher order eigenmodes of the microcantilever. The ability to control these modes and their responses to excitation is believed to be the key to unraveling the true potential of these methods. In this work, we highlight a multi-mode Q control method that exhibits remarkable damping performance and stability robustness. The experimental results obtained in ambient conditions demonstrate improved imaging stability by damping non-driven resonant modes when scanning is performed at a higher eigenmode of the cantilever. Higher scan speeds are shown to result from a decrease in transient response time. }, keywords = {}, pubstate = {published}, tppubtype = {article} } Numerous dynamic Atomic Force Microscopy (AFM) methods have appeared in recent years, which make use of the excitation and detection of higher order eigenmodes of the microcantilever. The ability to control these modes and their responses to excitation is believed to be the key to unraveling the true potential of these methods. In this work, we highlight a multi-mode Q control method that exhibits remarkable damping performance and stability robustness. The experimental results obtained in ambient conditions demonstrate improved imaging stability by damping non-driven resonant modes when scanning is performed at a higher eigenmode of the cantilever. Higher scan speeds are shown to result from a decrease in transient response time. |
| 8. |  | M. G. Ruppert; D. M. Harcombe; S. O. R. Moheimani State estimation for high-speed multifrequency atomic force microscopy Inproceedings American Control Conference, pp. 2617-2622, Boston, MA, USA, 2016. @inproceedings{Ruppert2016b, title = {State estimation for high-speed multifrequency atomic force microscopy}, author = {M. G. Ruppert and D. M. Harcombe and S. O. R. Moheimani}, doi = {10.1109/ACC.2016.7525311}, year = {2016}, date = {2016-07-01}, booktitle = {American Control Conference}, pages = {2617-2622}, address = {Boston, MA, USA}, abstract = {A fundamental component in the z-axis feedback loop of an atomic force microscope (AFM) operated in dynamic mode is the lock-in amplifier to obtain amplitude and phase of the high-frequency cantilever deflection signal. While this narrowband demodulation technique is capable of filtering noise far away from the carrier and modulation frequency, its performance is ultimately bounded by the bandwidth of its low-pass filter which is employed to suppress the frequency component at twice the carrier frequency. Moreover, multiple eigenmodes and higher harmonics are used for imaging in modern multifrequency AFMs, which necessitates multiple lock-in amplifiers to recover the respective amplitude and phase information. We propose to estimate amplitude and phase of multiple frequency components with a linear time-varying Kalman filter which allows for an efficient implementation on a Field Programmable Gate Array (FPGA). While experimental results for the single mode case have already proven to increase the imaging bandwidth in tapping-mode AFM, multifrequency simulations promise further improvement in imaging flexibility. }, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } A fundamental component in the z-axis feedback loop of an atomic force microscope (AFM) operated in dynamic mode is the lock-in amplifier to obtain amplitude and phase of the high-frequency cantilever deflection signal. While this narrowband demodulation technique is capable of filtering noise far away from the carrier and modulation frequency, its performance is ultimately bounded by the bandwidth of its low-pass filter which is employed to suppress the frequency component at twice the carrier frequency. Moreover, multiple eigenmodes and higher harmonics are used for imaging in modern multifrequency AFMs, which necessitates multiple lock-in amplifiers to recover the respective amplitude and phase information. We propose to estimate amplitude and phase of multiple frequency components with a linear time-varying Kalman filter which allows for an efficient implementation on a Field Programmable Gate Array (FPGA). While experimental results for the single mode case have already proven to increase the imaging bandwidth in tapping-mode AFM, multifrequency simulations promise further improvement in imaging flexibility. |
| 7. |  | M. G. Ruppert; S. O. R. Moheimani High-bandwidth Multimode Self-sensing in Bimodal Atomic Force Microscopy Journal Article Beilstein Journal of Nanotechnology, 7 , pp. 284-295, 2016. @article{Ruppert2016b, title = {High-bandwidth Multimode Self-sensing in Bimodal Atomic Force Microscopy}, author = {M. G. Ruppert and S. O. R. Moheimani}, doi = {10.3762/bjnano.7.26}, year = {2016}, date = {2016-02-24}, journal = {Beilstein Journal of Nanotechnology}, volume = {7}, pages = {284-295}, abstract = {Using standard microelectromechanical system (MEMS) processes to coat a microcantilever with a piezoelectric layer results in a versatile transducer with inherent self-sensing capabilities. For applications in multifrequency atomic force microscopy (MF-AFM), we illustrate that a single piezoelectric layer can be simultaneously used for multimode excitation and detection of the cantilever deflection. This is achieved by a charge sensor with a bandwidth of 10 MHz and dual feedthrough cancellation to recover the resonant modes that are heavily buried in feedthrough originating from the piezoelectric capacitance. The setup enables the omission of the commonly used piezoelectric stack actuator and optical beam deflection sensor, alleviating limitations due to distorted frequency responses and instrumentation cost, respectively. The proposed method benefits from a more than two orders of magnitude increase in deflection to strain sensitivity on the fifth eigenmode leading to a remarkable signal-to-noise ratio. Experimental results using bimodal AFM imaging on a two component polymer sample validate that the self-sensing scheme can therefore be used to provide both the feedback signal, for topography imaging on the fundamental mode, and phase imaging on the higher eigenmode.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Using standard microelectromechanical system (MEMS) processes to coat a microcantilever with a piezoelectric layer results in a versatile transducer with inherent self-sensing capabilities. For applications in multifrequency atomic force microscopy (MF-AFM), we illustrate that a single piezoelectric layer can be simultaneously used for multimode excitation and detection of the cantilever deflection. This is achieved by a charge sensor with a bandwidth of 10 MHz and dual feedthrough cancellation to recover the resonant modes that are heavily buried in feedthrough originating from the piezoelectric capacitance. The setup enables the omission of the commonly used piezoelectric stack actuator and optical beam deflection sensor, alleviating limitations due to distorted frequency responses and instrumentation cost, respectively. The proposed method benefits from a more than two orders of magnitude increase in deflection to strain sensitivity on the fifth eigenmode leading to a remarkable signal-to-noise ratio. Experimental results using bimodal AFM imaging on a two component polymer sample validate that the self-sensing scheme can therefore be used to provide both the feedback signal, for topography imaging on the fundamental mode, and phase imaging on the higher eigenmode. |
| 6. |  | M. G. Ruppert; K. S. Karvinen; S. L. Wiggins; S. O. R. Moheimani A Kalman Filter for Amplitude Estimation in High-Speed Dynamic Mode Atomic Force Microscopy Journal Article IEEE Transactions on Control Systems Technology, 24 (1), pp. 276-284, 2016. @article{Ruppert2016b, title = {A Kalman Filter for Amplitude Estimation in High-Speed Dynamic Mode Atomic Force Microscopy}, author = {M. G. Ruppert and K. S. Karvinen and S. L. Wiggins and S. O. R. Moheimani}, doi = {10.1109/TCST.2015.2435654}, year = {2016}, date = {2016-01-01}, journal = {IEEE Transactions on Control Systems Technology}, volume = {24}, number = {1}, pages = {276-284}, abstract = {A fundamental challenge in dynamic mode atomic force microscopy (AFM) is the estimation of the cantilever oscillation amplitude from the deflection signal which might be distorted by noise and/or high-frequency components. When the cantilever is excited at resonance, its deflection is typically obtained via narrowband demodulation using a lock-in amplifier. However, the bandwidth of this measurement technique is ultimately bounded by the low-pass filter which must be employed after demodulation to attenuate the component at twice the carrier frequency. Furthermore, to measure the amplitude of multiple frequency components such as higher eigenmodes and/or higher harmonics in multifrequency AFM, multiple lock-in amplifiers must be employed. In this work, the authors propose the estimation of amplitude and phase using a linear time-varying Kalman filter which is easily extended to multiple frequencies. Experimental results are obtained using square-modulated sine waves and closed-loop AFM scans, verifying the performance of the proposed Kalman filter.}, keywords = {}, pubstate = {published}, tppubtype = {article} } A fundamental challenge in dynamic mode atomic force microscopy (AFM) is the estimation of the cantilever oscillation amplitude from the deflection signal which might be distorted by noise and/or high-frequency components. When the cantilever is excited at resonance, its deflection is typically obtained via narrowband demodulation using a lock-in amplifier. However, the bandwidth of this measurement technique is ultimately bounded by the low-pass filter which must be employed after demodulation to attenuate the component at twice the carrier frequency. Furthermore, to measure the amplitude of multiple frequency components such as higher eigenmodes and/or higher harmonics in multifrequency AFM, multiple lock-in amplifiers must be employed. In this work, the authors propose the estimation of amplitude and phase using a linear time-varying Kalman filter which is easily extended to multiple frequencies. Experimental results are obtained using square-modulated sine waves and closed-loop AFM scans, verifying the performance of the proposed Kalman filter. |
2015 |
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| 5. |  | M. G. Ruppert; S. O. R. Moheimani Multi-Mode Q Control in Multifrequency Atomic Force Microscopy Inproceedings ASME International Design Engineering Technical Conferences & Computers and Information in Engineering Conference, pp. V004T09A009, Boston, Massachusetts, USA, 2015. @inproceedings{Ruppert2015, title = {Multi-Mode Q Control in Multifrequency Atomic Force Microscopy}, author = {M. G. Ruppert and S. O. R. Moheimani}, doi = {10.1115/DETC2015-46989}, year = {2015}, date = {2015-08-01}, booktitle = {ASME International Design Engineering Technical Conferences & Computers and Information in Engineering Conference}, pages = {V004T09A009}, address = {Boston, Massachusetts, USA}, abstract = {Various Atomic Force Microscopy (AFM) modes have emerged which rely on the excitation and detection of multiple eigenmodes of the microcantilever. The conventional control loops employed in multifrequency AFM (MF-AFM) such as bimodal imaging where the fundamental mode is used to map the topography and a higher eigenmode is used to map sample material properties only focus on maintaining low bandwidth signals such as amplitude and/ or frequency shift. However, the ability to perform additional high bandwidth control of the quality (Q) factor of the participating modes is believed to be imperative to unfolding the full potential of these methods. This can be achieved by employing a multi-mode Q control approach utilizing positive position feedback. The controller exhibits remarkable performance in arbitrarily modifying the Q factor of multiple eigenmodes as well as guaranteed stability properties when used on flexible structures with collocated actuators and sensors. A controller design method based on pole placement optimization is proposed for setting an arbitrary on-resonance Q factor of the participating eigenmodes. Experimental results using bimodal AFM imaging on a two component polymer sample are presented.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } Various Atomic Force Microscopy (AFM) modes have emerged which rely on the excitation and detection of multiple eigenmodes of the microcantilever. The conventional control loops employed in multifrequency AFM (MF-AFM) such as bimodal imaging where the fundamental mode is used to map the topography and a higher eigenmode is used to map sample material properties only focus on maintaining low bandwidth signals such as amplitude and/ or frequency shift. However, the ability to perform additional high bandwidth control of the quality (Q) factor of the participating modes is believed to be imperative to unfolding the full potential of these methods. This can be achieved by employing a multi-mode Q control approach utilizing positive position feedback. The controller exhibits remarkable performance in arbitrarily modifying the Q factor of multiple eigenmodes as well as guaranteed stability properties when used on flexible structures with collocated actuators and sensors. A controller design method based on pole placement optimization is proposed for setting an arbitrary on-resonance Q factor of the participating eigenmodes. Experimental results using bimodal AFM imaging on a two component polymer sample are presented. |
2014 |
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| 4. |  | K. S. Karvinen; M. G. Ruppert; K. Mahata; S. O. R. Moheimani Direct Tip-Sample Force Estimation for High-Speed Dynamic Mode Atomic Force Microscopy Journal Article IEEE Transactions on Nanotechnology, 13 (6), pp. 1257-1265, 2014. @article{Karvinen2014, title = {Direct Tip-Sample Force Estimation for High-Speed Dynamic Mode Atomic Force Microscopy}, author = {K. S. Karvinen and M. G. Ruppert and K. Mahata and S. O. R. Moheimani}, doi = {10.1109/TNANO.2014.2360878}, year = {2014}, date = {2014-11-01}, journal = {IEEE Transactions on Nanotechnology}, volume = {13}, number = {6}, pages = {1257-1265}, abstract = {We present new insights into the modeling of the microcantilever in dynamic mode atomic force microscopy and outline a novel high-bandwidth tip-sample force estimation technique for the development of high-bandwidth z-axis control. Fundamental to the proposed technique is the assumption that in tapping mode atomic force microscopy, the tip-sample force takes the form of an impulse train. Formulating the estimation problem as a Kalman filter, the tip-sample force is estimated directly; thus, potentially enabling high-bandwidth z-axis control by eliminating the dependence of the control technique on microcantilever dynamics and the amplitude demodulation technique. Application of this technique requires accurate knowledge of the models of the microcantilever; a novel identification method is proposed. Experimental data are used in an offline analysis for verification.}, keywords = {}, pubstate = {published}, tppubtype = {article} } We present new insights into the modeling of the microcantilever in dynamic mode atomic force microscopy and outline a novel high-bandwidth tip-sample force estimation technique for the development of high-bandwidth z-axis control. Fundamental to the proposed technique is the assumption that in tapping mode atomic force microscopy, the tip-sample force takes the form of an impulse train. Formulating the estimation problem as a Kalman filter, the tip-sample force is estimated directly; thus, potentially enabling high-bandwidth z-axis control by eliminating the dependence of the control technique on microcantilever dynamics and the amplitude demodulation technique. Application of this technique requires accurate knowledge of the models of the microcantilever; a novel identification method is proposed. Experimental data are used in an offline analysis for verification. |
| 3. |  | M. G. Ruppert; S. O. R. Moheimani Novel Reciprocal Self-Sensing Techniques for Tapping-Mode Atomic Force Microscopy Inproceedings 19th IFAC World Congress, Cape Town, South Africa, 2014. @inproceedings{Ruppert2014, title = {Novel Reciprocal Self-Sensing Techniques for Tapping-Mode Atomic Force Microscopy}, author = {M. G. Ruppert and S. O. R. Moheimani}, doi = {https://doi.org/10.3182/20140824-6-ZA-1003.00376}, year = {2014}, date = {2014-08-24}, booktitle = {19th IFAC World Congress}, address = {Cape Town, South Africa}, abstract = {We evaluate two novel reciprocal self-sensing methods for tapping-mode atomic force microscopy (TM-AFM) utilizing charge measurement and charge actuation, respectively. A microcantilever, which can be batch fabricated through a standard microelectromechanical system (MEMS) process, is coated with a single piezoelectric layer and simultaneously used for actuation and deflection sensing. The setup enables the elimination of the optical beam deflection technique which is commonly used to measure the cantilever oscillation amplitude. The voltage to charge and charge to voltage transfer functions reveal a high amount of capacitive feedthrough which degrades the dynamic range of the sensors significantly. A feedforward control technique is employed to cancel the feedthrough and increase the dynamic range from less than 1 dB to approximately 30 dB. Experiments show that the conditioned self-sensing schemes achieve an excellent signal-to-noise ratio and can therefore be used to provide the feedback signal for TM-AFM imaging.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } We evaluate two novel reciprocal self-sensing methods for tapping-mode atomic force microscopy (TM-AFM) utilizing charge measurement and charge actuation, respectively. A microcantilever, which can be batch fabricated through a standard microelectromechanical system (MEMS) process, is coated with a single piezoelectric layer and simultaneously used for actuation and deflection sensing. The setup enables the elimination of the optical beam deflection technique which is commonly used to measure the cantilever oscillation amplitude. The voltage to charge and charge to voltage transfer functions reveal a high amount of capacitive feedthrough which degrades the dynamic range of the sensors significantly. A feedforward control technique is employed to cancel the feedthrough and increase the dynamic range from less than 1 dB to approximately 30 dB. Experiments show that the conditioned self-sensing schemes achieve an excellent signal-to-noise ratio and can therefore be used to provide the feedback signal for TM-AFM imaging. |
2013 |
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| 2. |  | M. G. Ruppert; S. O. R. Moheimani A novel self-sensing technique for tapping-mode atomic force microscopy Journal Article Review of Scientific Instruments, 84 (12), pp. 125006, 2013. @article{Ruppert2013b, title = {A novel self-sensing technique for tapping-mode atomic force microscopy}, author = {M. G. Ruppert and S. O. R. Moheimani}, doi = {http://dx.doi.org/10.1063/1.4841855}, year = {2013}, date = {2013-12-01}, journal = {Review of Scientific Instruments}, volume = {84}, number = {12}, pages = {125006}, abstract = {This work proposes a novel self-sensing tapping-mode atomic force microscopy operation utilizing charge measurement. A microcantilever coated with a single piezoelectric layer is simultaneously used for actuation and deflection sensing. The cantilever can be batch fabricated with existing Micro Electro Mechanical System processes. The setup enables the omission of the optical beam deflection technique which is commonly used to measure the cantilever oscillation amplitude. Due to the high amount of capacitive feedthrough in the measured charge signal, a feedforward control technique is employed to increase the dynamic range from less than 1dB to approximately 35dB. Experiments show that the conditioned charge signal achieves excellent signal-to-noise ratio and can therefore be used as a feedback signal for AFM imaging.}, keywords = {}, pubstate = {published}, tppubtype = {article} } This work proposes a novel self-sensing tapping-mode atomic force microscopy operation utilizing charge measurement. A microcantilever coated with a single piezoelectric layer is simultaneously used for actuation and deflection sensing. The cantilever can be batch fabricated with existing Micro Electro Mechanical System processes. The setup enables the omission of the optical beam deflection technique which is commonly used to measure the cantilever oscillation amplitude. Due to the high amount of capacitive feedthrough in the measured charge signal, a feedforward control technique is employed to increase the dynamic range from less than 1dB to approximately 35dB. Experiments show that the conditioned charge signal achieves excellent signal-to-noise ratio and can therefore be used as a feedback signal for AFM imaging. |
| 1. |  | M. G. Ruppert; M. Fairbairn; S. O. R. Moheimani Multi-Mode Resonant Control of a Microcantilever for Atomic Force Microscopy Inproceedings IEEE/ASME International Conference on Advanced Intelligent Mechatronics, pp. 77-82, Wollongong, Australia, 2013. @inproceedings{Ruppert2013, title = {Multi-Mode Resonant Control of a Microcantilever for Atomic Force Microscopy}, author = {M. G. Ruppert and M. Fairbairn and S. O. R. Moheimani}, doi = {10.1109/AIM.2013.6584071}, year = {2013}, date = {2013-07-09}, booktitle = {IEEE/ASME International Conference on Advanced Intelligent Mechatronics}, pages = {77-82}, address = {Wollongong, Australia}, abstract = {When operating the Atomic Force Microscope in tapping mode it is possible to decrease the quality factor of the microcantilever to enhance scan speed. %Standard Q Control techniques involve velocity feedback with the disadvantage of additional sensor equipment, or time-delay position feedback which may lead to instabilities of out-of-bandwidth modes.Various resonance controllers have been proposed which do not rely on expensive velocity sensors and guarantee stability of the closed loop system even in the presence of unmodeled dynamics. A new field of Atomic Force Microscopy is evolving, which makes use of multiple frequency excitation and detection of the cantilever modes making it necessary to be able to control these modes and their response to excitation. This work proposes a multi-mode Q control approach utilizing positive position feedback, offering full control over the first two flexural modes of the cantilever. By completely damping the first mode and adjusting the quality factor of the second mode, it is possible to scan and obtain images at the second resonance frequency which improves image quality at high scan speeds due to the increased bandwidth of the z-axis feedback loop.}, keywords = {}, pubstate = {published}, tppubtype = {inproceedings} } When operating the Atomic Force Microscope in tapping mode it is possible to decrease the quality factor of the microcantilever to enhance scan speed. %Standard Q Control techniques involve velocity feedback with the disadvantage of additional sensor equipment, or time-delay position feedback which may lead to instabilities of out-of-bandwidth modes.Various resonance controllers have been proposed which do not rely on expensive velocity sensors and guarantee stability of the closed loop system even in the presence of unmodeled dynamics. A new field of Atomic Force Microscopy is evolving, which makes use of multiple frequency excitation and detection of the cantilever modes making it necessary to be able to control these modes and their response to excitation. This work proposes a multi-mode Q control approach utilizing positive position feedback, offering full control over the first two flexural modes of the cantilever. By completely damping the first mode and adjusting the quality factor of the second mode, it is possible to scan and obtain images at the second resonance frequency which improves image quality at high scan speeds due to the increased bandwidth of the z-axis feedback loop. |