Publications

@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 = {AFM, Cantilever, MEMS, Multifrequency AFM, Smart Structures, SPM, Vibration Control},

pubstate = {published},

tppubtype = {article}

}

@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 = {Cantilever, MEMS, Multifrequency AFM, Sensors, Smart Structures, SPM, System Identification, Vibration Control},

pubstate = {published},

tppubtype = {article}

}

@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 = {https://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 = {AFM, Cantilever, MEMS, Multifrequency AFM, Piezoelectric Transducers and Drives, System Identification, Vibration Control},

pubstate = {published},

tppubtype = {article}

}

@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 = {MEMS, Multifrequency AFM, SPM, System Identification, Vibration Control},

pubstate = {published},

tppubtype = {article}

}

@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 = {MEMS, Multifrequency AFM, Piezoelectric Transducers and Drives, Vibration Control},

pubstate = {published},

tppubtype = {article}

}

@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 = {Multifrequency AFM, SPM, Vibration Control},

pubstate = {published},

tppubtype = {article}

}

@article{J06a,

title = {Inertial vibration control using a shunted electromagnetic transducer},

author = {A. J. Fleming and S. Behrens and S. O. R. Moheimani},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J06a.pdf},

year  = {2006},

date = {2006-12-01},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {11},

number = {1},

pages = {84--92},

keywords = {Vibration Control},

pubstate = {published},

tppubtype = {article}

}

@article{J06c,

title = {Adaptive electromagnetic shunt damping},

author = {D. Niederberger and S. Behrens and A. J. Fleming and S. O. R. Moheimani and M. Morari},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J06c.pdf},

year  = {2006},

date = {2006-12-01},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {11},

number = {1},

pages = {103--108},

keywords = {Vibration Control},

pubstate = {published},

tppubtype = {article}

}

@article{J05a,

title = {Synthesis and implementation of sensor-less active shunt controllers for electromagnetically actuated systems},

author = {A. J. Fleming and S. Behrens and S. O. R. Moheimani},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J05a.pdf},

year  = {2005},

date = {2005-12-01},

journal = {IEEE Transactions on Control Systems Technology},

volume = {13},

number = {2},

pages = {246--261},

keywords = {Vibration Control},

pubstate = {published},

tppubtype = {article}

}

@article{J05b,

title = {Passive vibration control via electromagnetic shunt damping},

author = {S. Behrens and A. J. Fleming and S. O. R. Moheimani},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J05b.pdf},

year  = {2005},

date = {2005-12-01},

journal = {IEEE/ASME Transactions on Mechatronics},

volume = {10},

number = {1},

pages = {118--122},

keywords = {Vibration Control},

pubstate = {published},

tppubtype = {article}

}