Publications

@article{McCourt2020,

title = {A comparison of gold and silver nanocones and geometry optimisation for tip-enhanced microscopy},

author = {L. McCourt and M. G. Ruppert and B. S. Routley and S. Indirathankam and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2020/09/J20e.pdf},

doi = {https://doi.org/10.1002/jrs.5987},

year  = {2020},

date = {2020-11-01},

urldate = {2020-08-24},

journal = {Journal of Raman Spectroscopy},

volume = {51},

issue = {11},

pages = {2208-2216},

abstract = {In this article, boundary element method simulations are used to optimise the geometry of silver and gold nanocone probes to maximise the localised electric field enhancement and tune the near-field resonance wavelength. These objectives are expected to maximise the sensitivity of tip-enhanced Raman microscopes. Similar studies have used limited parameter sets or used a performance metric other than localised electric field enhancement. In this article, the optical responses for a range of nanocone geometries are simulated for excitation wavelengths ranging from 400 to 1000 nm. Performance is evaluated by measuring the electric field enhancement at the sample surface with a resonant illumination wavelength. These results are then used to determine empirical models and derive optimal nanocone geometries for a particular illumination wavelength and tip material. This article concludes that gold nanocones are expected to provide similar performance to silver nanocones at red and nearinfrared wavelengths, which is consistent with other results in the literature. In this article, 633 nm is determined to be the shortest usable illumination wavelength for gold nanocones. Below this limit, silver nanocones will provide superior enhancement. The use of gold nanocone probes is expected to dramatically improve probe lifetime, which is currently measured in hours for silver coated probes. Furthermore, the elimination of passivation coatings is expected to enable smaller probe radii and improved topographical resolution.},

keywords = {AFM, Cantilever, MEMS, Optics, SPM},

pubstate = {published},

tppubtype = {article}

}

@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},

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

keywords = {AFM, Cantilever, DP170101813, MEMS, Multifrequency AFM, Smart Structures, SPM, Vibration Control},

pubstate = {published},

tppubtype = {article}

}

@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 = {https://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 = {AFM, Demodulation, Multifrequency AFM, SPM},

pubstate = {published},

tppubtype = {article}

}

@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 = {AFM, Nanopositioning, Scan Pattern, SPM, Tracking Control},

pubstate = {published},

tppubtype = {article}

}

@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},

urldate = {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.},

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

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

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{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 = {AFM, Nanopositioning, SPM, System Identification, Tracking Control},

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}

}

@article{J18f,

title = {A Comparison Of Scanning Methods And The Vertical Control Implications For Scanning Probe Microscopy},

author = {Y. R. Teo and Y. K. Yong and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2021/02/J18f.pdf},

doi = {10.1002/asjc.1422},

year  = {2018},

date = {2018-07-01},

journal = {Asian Journal of Control},

volume = {30},

number = {4},

pages = {1-15},

abstract = {This article compares the imaging performance of non-traditional scanning patterns for scanning probe microscopy including sinusoidal raster, spiral, and Lissajous patterns. The metrics under consideration include the probe velocity, scanning frequency, and required sampling rate. The probe velocity is investigated in detail as this quantity is proportional to the required bandwidth of the vertical feedback loop and has a major impact on image quality. By considering a sample with an impulsive Fourier transform, the effect of scanning trajectories on imaging quality can be observed and quantified. The non-linear trajectories are found to spread the topography signal bandwidth which has important implications for both low and high-speed imaging. These effects are studied analytically and demonstrated experimentally with a periodic calibration grating. },

keywords = {Scan Pattern, SPM},

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{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 = {https://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 = {AFM, SPM},

pubstate = {published},

tppubtype = {article}

}

@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 = {https://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 = {AFM, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{Moore2017,

title = {Design and Characterization of Cantilevers for Multi-Frequency Atomic Force Microscopy},

author = {S. I. Moore and Y. K. Yong},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/01/MNL.2016.0586.pdf},

doi = {10.1049/mnl.2016.0586},

year  = {2017},

date = {2017-03-01},

urldate = {2017-03-01},

journal = {Micro & Nano Letters},

volume = {12},

number = {5},

pages = {315-320},

abstract = {The experimental characterisation of a set of microcantilevers targeted at use in multi-frequency atomic force microscope is presented. The aim of this work is to design a cantilever that naturally amplifies its harmonic oscillations which are introduced by nonlinear probe–sample

interaction forces. This is performed by placing the modal frequencies of the cantilever at integer multiples of the first modal frequency. The developed routine demonstrates the placement of the frequency of the second to fifth mode. The characterisation shows a trend that

lower-order modes are more accurately placed than higher-order modes. With two fabricated designs, the error in the second mode is at most 2.26% while the greatest error in the fifth mode is at 10.5%.},

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

keywords = {Cantilever, DP170101813, MEMS, Multifrequency AFM, SPM},

pubstate = {published},

tppubtype = {article}

}

@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 = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/02/2190-4286-8-38.pdf},

year  = {2017},

date = {2017-02-06},

urldate = {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.},

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

keywords = {Cantilever, DP170101813, Multifrequency AFM, Piezoelectric Transducers and Drives, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{Bazaei2017,

title = {Combining Spiral Scanning and Internal Model Control for Sequential AFM Imaging at Video Rate},

author = {A. Bazaei and Y. K. Yong and S. O. R. Moheimani },

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2017/05/07482697.pdf},

year  = {2017},

date = {2017-02-01},

journal = {IEEE Transactions on Mechatronics},

volume = {22},

number = {1},

pages = {371-380},

abstract = {We report on the application of internal model control for accurate tracking of a spiral trajectory for atomic force microscopy (AFM). With a closed-loop bandwidth of only 300 Hz, we achieved tracking errors as low as 0.31% of the scan diameter and an ultravideo frame rate for a high pitch (30 nm) spiral trajectory generated by amplitude modulation of 3 kHz sinusoids. Design and synthesis procedures are proposed for a smooth modulating waveform to minimize the steady-state tracking error during sequential imaging. To obtain AFM images under the constant force condition, a high bandwidth analogue proportional integral controller is applied to the damped z-axis of a flexure nanopositioner. Efficacy of the proposed method was  demonstrated by artifact-free images at a rate of 37.5 frames/s.},

keywords = {Scan Pattern, SPM},

pubstate = {published},

tppubtype = {article}

}

@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 = {MEMS, Nanopositioning, Piezoelectric Transducers and Drives, Sensors, Smart Structures, SPM, Tracking Control},

pubstate = {published},

tppubtype = {article}

}

@article{J16d,

title = {High-speed Vertical Positioning Stage with Integrated Dual-sensor Arrangement},

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

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2016/08/1-s2.0-S0924424716303302-main-1.pdf},

doi = {https://doi.org/10.1016/j.sna.2016.06.042},

year  = {2016},

date = {2016-12-01},

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

volume = {248},

pages = {184--192},

abstract = {This article presents a novel vertical positioning stage with a dual-sensor arrangement suitable for scanning probe microscopy. The stage has a travel range of 8.4um and a first resonance frequency of 24kHz in the direction of travel. The sensor arrangement consists of an integrated piezoelectric force sensor and laminated piezoresistive strain sensor. The piezoelectric force sensor exhibits extremely low noise and introduces a zero into the dynamics which allows the use of integral force feedback. This control method provides excellent damping performance and guaranteed stability. The piezoresistive sensor is used for tracking control with an analog PI controller which is shown to be an approximate inverse of the damped system. The resulting closed-loop system has a bandwidth is 11.4kHz and 6-sigma resolution of 3.6nm, which is ideal for nanopositioning and atomic force microscopy (AFM) applications. The proposed vertical stage is used to replace the vertical axis of a commercial AFM. Scans are performed in constant-force contact mode with a tip velocity of 0.2mm/s, 1mm/s and 2mm/s. The recorded images contain negligible artefacts due to insufficient vertical bandwidth.},

keywords = {Nanopositioning, Optics, SPM},

pubstate = {published},

tppubtype = {article}

}

@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 = {Multifrequency AFM, SPM},

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 = {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{J15e,

title = {Low-order Damping and Tracking Control for Scanning Probe Systems},

author = {A. J. Fleming and Y. R. Teo and K. K. Leang

},

url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2015/12/J15e.pdf},

doi = {10.3389/fmech.2015.00014},

year  = {2015},

date = {2015-12-30},

journal = {Frontiers in Mechanical Engineering},

volume = {1},

pages = {1-9},

abstract = {This article describes an improvement to integral resonance damping control (IRC) for reference tracking applications such as Scanning Probe Microscopy and nanofabrication. It is demonstrated that IRC control introduces a low-frequency pole into the tracking loop which is detrimental for performance. In this work, the location of this pole is found analytically using Cardano’s method then compensated by parameterizing the tracking controller accordingly. This approach maximizes the closed-loop bandwidth whilst being robust to changes in the resonance frequencies. The refined IRC controller is comprehensively compared to other low-order methods in a practical environment.},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{Yong2015,

title = {Collocated Z-Axis Control of a High-Speed Nanopositioner for Video-Rate Atomic Force Microscopy},

author = {Y. K. Yong and S. O. R. Moheimani},

url = {http://www.eng.newcastle.edu.au/~yy582/Papers/Yong%202015%20-collocated%20Z-axis%20control.pdf},

doi = {10.1109/TNANO.2015.2394327},

issn = {1536-125X},

year  = {2015},

date = {2015-03-01},

journal = {IEEE Transactions on Nanotechnology},

volume = {14},

number = {2},

pages = {338-345},

abstract = {A key hurdle to achieve video-rate atomic force microscopy (AFM) in constant-force contact mode is the inadequate bandwidth of the vertical feedback control loop. This paper describes techniques used to increase the vertical tracking bandwidth of a nanopositioner to a level that is sufficient for video-rate AFM. These techniques involve the combination of: a high-speed XYZ nanopositioner; a passive damping technique that cancels the inertial forces of the Z actuator which in turns eliminates the low 20-kHz vertical resonant mode of the nanopositioner; an active control technique that is used to augment damping to high vertical resonant modes at 60 kHz and above. The implementation of these techniques allows a tenfold increase in the vertical tracking bandwidth, from 2.3 (without damping) to 28.1 kHz. This allows high-quality, video-rate AFM images to be captured at 10 frames/s without noticeable artifacts associated with vibrations and insufficient vertical tracking bandwidth.},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@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 = {SPM, System Identification},

pubstate = {published},

tppubtype = {article}

}

@article{Yong201485,

title = {Video-rate lissajous-scan atomic force microscopy},

author = {Y. K. Yong and A. Bazaei and S. O. R. Moheimani},

url = {http://www.eng.newcastle.edu.au/~yy582/Papers/Yong2014%20-%20Video-rate%20Lissajous.pdf},

doi = {10.1109/TNANO.2013.2292610},

year  = {2014},

date = {2014-01-01},

journal = {IEEE Transactions on Nanotechnology},

volume = {13},

number = {1},

pages = {85-93},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{Wadikhaye2014,

title = {Control of a piezoelectrically actuated high-speed serial-kinematic AFM nanopositioner},

author = {S. P. Wadikhaye and Y. K. Yong and B. Bhikkaji and S. O. R. Moheimani},

url = {http://www.eng.newcastle.edu.au/~yy582/Papers/Wadikhaye2014.pdf},

year  = {2014},

date = {2014-01-01},

journal = {Smart Materials and Structures},

volume = {23},

number = {2},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@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 = {MEMS, Smart Structures, SPM, System Identification},

pubstate = {published},

tppubtype = {article}

}

@article{Bazaei2012,

title = {High-speed Lissajous-scan atomic force microscopy: Scan pattern planning and control design issues},

author = {A. Bazaei and Y. K. Yong and S. O. R. Moheimani},

url = {http://www.eng.newcastle.edu.au/~yy582/Papers/High-speed_liss.pdf},

doi = {10.1063/1.4725525},

year  = {2012},

date = {2012-01-01},

journal = {Review of Scientific Instruments},

volume = {83},

number = {063701},

pages = {(1-10)},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{Wadikhaye2012309,

title = {Design of a compact serial-kinematic scanner for high-speed atomic force microscopy: An analytical approach},

author = {S. P. Wadikhaye and Y. K. Yong and S. O. R. Moheimani},

url = {http://www.eng.newcastle.edu.au/~yy582/Papers/Serial_kinematic.pdf},

doi = {10.1049/mnl.2011.0477},

year  = {2012},

date = {2012-01-01},

journal = {Micro and Nano Letters},

volume = {7},

number = {4},

pages = {309-313},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J11b,

title = {A compact ultra-fast vertical nanopositioner for improving SPM scan speed},

author = {B. J. Kenton and A. J. Fleming and K. K. Leang},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J11b.pdf},

year  = {2011},

date = {2011-12-01},

journal = {Review of Scientific Instruments},

volume = {82},

number = {12},

pages = {123703(1-8)},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J11a,

title = {Dual-stage vertical feedback for high speed-scanning probe microscopy},

author = {A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J11a.pdf},

year  = {2011},

date = {2011-12-01},

journal = {IEEE Transactions on Control Systems Technology},

volume = {19},

number = {1},

pages = {156--165},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J11c,

title = {Q control of an atomic force microscope micro-cantilever: a sensor-less approach},

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

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J11c.pdf},

year  = {2011},

date = {2011-12-01},

journal = {IEEE/ASME Journal of Microelectromechanical Systems},

volume = {20},

number = {6},

pages = {1372--1381},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J10d,

title = {A new method for robust damping and tracking control of scanning probe microscope positioning stages},

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

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J10d.pdf},

year  = {2010},

date = {2010-12-01},

journal = {IEEE Transactions on Nanotechnology},

volume = {9},

number = {4},

pages = {438--448},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J10c,

title = {Bridging the gap between conventional and video-speed scanning probe microscopes},

author = {A. J. Fleming and B. J. Kenton and K. K. Leang},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J10c.pdf},

year  = {2010},

date = {2010-12-01},

journal = {Ultramicroscopy},

volume = {110},

number = {9},

pages = {1205--1214},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J10b,

title = {Integrated strain and force feedback for high performance control of piezoelectric actuators},

author = {A. J. Fleming and K. K. Leang},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J10b.pdf},

year  = {2010},

date = {2010-12-01},

journal = {Sensors and Actuators A},

volume = {161},

number = {1-2},

pages = {256--265},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J10f,

title = {Quantitative SPM topographies by charge linearization of the vertical actuator},

author = {A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J10f.pdf},

year  = {2010},

date = {2010-12-01},

journal = {Review of Scientific Instruments},

volume = {81},

number = {10},

pages = {103701(1-5)},

crossref = {(Featured in the Virtual Journal of Nanoscale Science)},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J09a,

title = {High-speed serial-kinematic AFM scanner: design and drive considerations},

author = {K. K. Leang and A. J. Fleming},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J09a.pdf},

year  = {2009},

date = {2009-12-01},

journal = {Asian Journal of Control},

volume = {11},

number = {2},

pages = {144-153},

crossref = {(Special Issue)},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J09b,

title = {Optimal periodic trajectories for band-limited systems},

author = {A. J. Fleming and A. G. Wills},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J09b.pdf},

year  = {2009},

date = {2009-12-01},

journal = {IEEE Transactions on Control Systems Technology},

volume = {13},

number = {3},

pages = {552-562},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J08e,

title = {Charge drives for scanning probe microscope positioning stages},

author = {A. J. Fleming and K. K. Leang},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J08e.pdf},

year  = {2008},

date = {2008-12-01},

journal = {Ultramicroscopy},

volume = {108},

number = {12},

pages = {1551-1557},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J08d,

title = {Sensor fusion for improved control of piezoelectric tube scanners},

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

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J08d.pdf},

year  = {2008},

date = {2008-12-01},

journal = {IEEE Transactions on Control Systems Technology},

volume = {15},

number = {6},

pages = {1265--6536},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J08a,

title = {Simulation of dynamics-coupling in piezoelectric tube scanners by reduced order finite element models},

author = {J. Maess and A. J. Fleming and F. Allgöwer},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J08a.pdf},

year  = {2008},

date = {2008-12-01},

journal = {Review of Scientific Instruments},

volume = {79},

pages = {015105(1-9)},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J07c,

title = {High speed nano-scale positioning using a piezoelectric tube actuator with active shunt control},

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

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J07c.pdf},

year  = {2007},

date = {2007-12-01},

journal = {IET Micro & Nano Letters},

volume = {2},

number = {1},

pages = {9--12},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J07d,

title = {High-performance control of piezoelectric tube scanners},

author = {B. Bhikkaji and M. Ratnam and A. J. Fleming and S. O. R. Moheimani},

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J07d.pdf},

year  = {2007},

date = {2007-12-01},

journal = {IEEE Transactions on Control Systems Technology},

volume = {15},

number = {5},

pages = {853-866},

crossref = {(Special Issue)},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J06b,

title = {Sensorless vibration suppression and scan compensation for piezoelectric tube nanopositioners},

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

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J06b.pdf},

year  = {2006},

date = {2006-12-01},

journal = {IEEE Transactions on Control Systems Technology},

volume = {14},

number = {1},

pages = {33--44},

keywords = {Nanopositioning, SPM},

pubstate = {published},

tppubtype = {article}

}

@article{J05d,

title = {A grounded load charge amplifier for reducing hysteresis in piezoelectric tube scanners},

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

url = {https://www.precisionmechatronicslab.com/wp-content/publications/J05d.pdf},

year  = {2005},

date = {2005-12-01},

journal = {Review of Scientific Instruments},

volume = {76},

number = {7},

pages = {073707(1-5)},

keywords = {Piezoelectric Transducers and Drives, SPM},

pubstate = {published},

tppubtype = {article}

}