Publications

@article{J22a,

title = {Simultaneous tip force and displacement sensing for AFM cantilevers with on-chip actuation: Design and characterization for off-resonance tapping mode},

author = {N. F. S. de Bem and M. G. Ruppert and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J22a.pdf},

doi = {10.1016/j.sna.2022.113496},

issn = {0924-4247},

year  = {2022},

date = {2022-03-08},

urldate = {2022-03-08},

journal = {Sensors and Actuators A: Physical},

volume = {338},

pages = {113496},

abstract = {The use of integrated on-chip actuation simplifies the identification of a cantilever resonance, can improve imaging speed, and enables the use of smaller cantilevers, which is required for low-force imaging at high speed. This article describes a cantilever with on-chip actuation and novel dual-sensing capabilities for AFM. The dual-sensing configuration allows for tip displacement and tip force to be measured simultaneously. A mathematical model is developed and validated with finite element analysis. A physical prototype is presented, and its calibration and validation are presented. The cantilever is optimized for use in off-resonance tapping modes. Experimental results demonstrate an agreement between the on-chip sensors and external force and displacement measurements.},

note = {This work was supported by the Australian Research Council Discovery Project DP170101813},

keywords = {AFM, DP170101813},

pubstate = {published},

tppubtype = {article}

}

@article{Ruppert2022,

title = {Experimental Analysis of Tip Vibrations at Higher Eigenmodes of QPlus Sensors for Atomic Force Microscopy},

author = {M. G. Ruppert and D. Martin-Jimenez and Y. K. Yong and A. Ihle and A. Schirmeisen and A. J. Fleming and D. Ebeling},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J22c.pdf},

doi = {10.1088/1361-6528/ac4759},

issn = {1361-6528},

year  = {2022},

date = {2022-02-10},

urldate = {2022-02-10},

journal = {Nanotechnology},

volume = {33},

issue = {18},

pages = {185503},

abstract = {QPlus sensors are non-contact atomic force microscope probes constructed from a quartz tuning fork and a tungsten wire with an electrochemically etched tip. These probes are self-sensing and offer an atomic-scale spatial resolution. Therefore, qPlus sensors are routinely used to visualize the chemical structure of adsorbed organic molecules via the so-called bond imaging technique. This is achieved by functionalizing the AFM tip with a single CO molecule and exciting the sensor at the first vertical cantilever resonance mode. Recent work using higher-order resonance modes has also resolved the chemical structure of single organic molecules. However, in these experiments, the image contrast can differ significantly from the conventional bond imaging contrast, which was suspected to be caused by unknown vibrations of the tip. This work investigates the source of these artefacts by using a combination of mechanical simulation and laser vibrometry to characterize a range of sensors with different tip wire geometries. The results show that increased tip mass and length cause increased torsional rotation of the tuning fork beam due to the off-center mounting of the tip wire, and increased flexural vibration of the tip. These undesirable motions cause lateral deflection of the probe tip as it approaches the sample, which is rationalized to be the cause of the different image contrast. The results also provide a guide for future probe development to reduce these issues.},

note = {This work was supported in part by the Australian Research Council Discovery Project DP170101813},

keywords = {Actuator, AFM, Cantilever, DP170101813, Multifrequency AFM, piezoelectric},

pubstate = {published},

tppubtype = {article}

}

@article{Ruppert2021,

title = {Active atomic force microscope cantilevers with integrated device layer piezoresistive sensors},

author = {M. G. Ruppert and A. J. Fleming and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2021/01/J21a.pdf},

doi = {10.1016/j.sna.2020.112519},

issn = {0924-4247},

year  = {2021},

date = {2021-01-19},

urldate = {2021-01-19},

journal = {Sensors & Actuators: A. Physical},

volume = {319},

pages = {112519},

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 optical beam deflection measurement. Active

microcantilevers exhibit a clean frequency response, provide a path-way to miniturization and parallelization and

avoid the need for optical alignment. However, active microcantilevers are presently limited by the feedthrough

between actuators and sensors, and by the cost associated with custom microfabrication. In this work, we propose

a hybrid cantilever design with integrated piezoelectric actuators and a piezoresistive sensor fabricated from the

silicon device layer without requiring an additional doping step. As a result, the design can be fabricated using a

commercial five-mask microelectromechanical systems fabrication process. The theoretical piezoresistor sensitivity

is compared with finite element simulations and experimental results obtained from a prototype device. The

proposed approach is demonstrated to be a promising alternative to conventional microcantilever actuation and

deflection sensing},

note = {This work was supported by the Australian Research Council Discovery Project DP170101813},

keywords = {AFM, Cantilever, DP170101813, MEMS, Sensors, Smart Structures},

pubstate = {published},

tppubtype = {article}

}

@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 = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/09/J20f.pdf},

doi = {10.1016/j.sna.2020.112092},

year  = {2020},

date = {2020-05-29},

urldate = {2020-05-29},

journal = {Sensors and Actuators A: Physical},

volume = {312},

pages = {112092},

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.},

note = {This work was supported by the Australian Research Council Discovery Project DP170101813},

keywords = {AFM, Cantilever, Demodulation, DP170101813, MEMS, System Identification},

pubstate = {published},

tppubtype = {article}

}

@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 = {https://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},

urldate = {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.},

note = {This work was supported by the Australian Research Council Discovery Project DP170101813},

keywords = {Demodulation, DP170101813, Multifrequency AFM, Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@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 = {https://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},

urldate = {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.},

note = {This work was supported by the Australian Research Council Discovery Project DP170101813},

keywords = {AFM, Cantilever, DP170101813, MEMS, Multifrequency AFM, Piezoelectric Transducers and Drives, Sensors, Smart Structures, SPM},

pubstate = {published},

tppubtype = {article}

}