Scanning Probe Microscopy
Probe Based Lithography
Probe based lithography involves creating nanometer sized features from photoresist and metal on conducting and semiconducting substrates. Near field optical, electrical and thermal fields are employed in combination with evaporation, etching and electroplating to provide high-speed alternatives for mask-less nanofabrication.
Nanopositioning
A nanopositioner is a electromechanical device for moving objects in three dimensions with atomic, or sub-atomic resolution. Nanopositioners are employed in applications such as imaging, fabrication and optics. This field encompasses mechanical design, sensor design, and control theory. More details.
Electroactive Optics
Piezoelectric actuators can be combined with mirrors, lenses and objectives to actively control the path and properties of an optical field or laser beam. High speed electro-optics are required for precision lasers, maskless lithography, and microscopy.
Precision Sensors
This project aims to study the fundamental limitations of capacitive, optical and magnetic position sensors. New techniques are under development to provide sub-atomic resolution over extremely wide bandwidth.
Biomedical Devices
An endoscopic pill robot is being developed for noninvasive imaging and intervention. The robot can be swallowed and includes power transmission, 6-Dimensional localization, and locomotion.
Piezo Actuators and Amplifiers

Piezo bender actuator with integrated 200V power electronics
Piezo Robotics
Due to their compact size and high efficiency, piezoelectric actuators are ideal for micro-actuation in bio-inspired robotics. This project is developing actuators and mechanics for a piezoelectric dragon-fly robot.
Jidling, C.; Fleming, A. J.; Wills, A. G.; Schon, T. B.
Memory efficient constrained optimization of scanning-beam lithography Journal Article
In: Optics Express, vol. 30, no. 12, pp. 20564–20579, 2022, ISSN: 1094-4087.
@article{J22g,
title = {Memory efficient constrained optimization of scanning-beam lithography},
author = {C. Jidling and A. J. Fleming and A. G. Wills and T. B. Schon},
url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/05/J22g.pdf},
doi = {10.1364/OE.457334},
issn = {1094-4087},
year = {2022},
date = {2022-06-01},
journal = {Optics Express},
volume = {30},
number = {12},
pages = {20564--20579},
abstract = {This article describes a memory efficient method for solving large-scale optimization problems that arise when planning scanning-beam lithography processes. These processes require the identification of an exposure pattern that minimizes the difference between a desired and predicted output image, subject to constraints. The number of free variables is equal to the number of pixels, which can be on the order of millions or billions in practical applications. The proposed method splits the problem domain into a number of smaller overlapping subdomains with constrained boundary conditions, which are then solved sequentially using a constrained gradient search method (L-BFGS-B). Computational time is reduced by exploiting natural sparsity in the problem and employing the fast Fourier transform for efficient gradient calculation. When it comes to the trade-off between memory usage and computational time we can make a different trade-off compared to previous methods, where the required memory is reduced by approximately the number of subdomains at the cost of more computations. In an example problem with 30 million variables, the proposed method reduces memory requirements by 67%; but increases computation time by 27%. Variations of the proposed method are expected to find applications in the planning of processes such as scanning laser lithography, scanning electron beam lithography, and focused ion beam deposition, for example.},
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}

Li, Linlin; Fleming, A. J.; Yong, Y. K.; Aphale, S. S.; Zhu, LiMin
High Performance Raster Scanning of Atomic Force Microscopy Using Model-free Repetitive Control Journal Article
In: Mechanical Systems and Signal Processing, vol. Prepress, 2022, ISSN: 0888-3270.
@article{J22f,
title = {High Performance Raster Scanning of Atomic Force Microscopy Using Model-free Repetitive Control},
author = {Linlin Li and A. J. Fleming and Y. K. Yong and S. S. Aphale and LiMin Zhu},
url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J22f-prepress.pdf},
doi = {10.1016/j.ymssp.2022.109027},
issn = {0888-3270},
year = {2022},
date = {2022-05-01},
urldate = {2022-05-01},
journal = {Mechanical Systems and Signal Processing},
volume = {Prepress},
abstract = {The image quality of an atomic force microscope depends on the tracking performance of the lateral X and Y axis positioner. To reduce the requirement for accurate system models, this article describes a method based on Model free Repetitive Control (MFRC) for high performance control of fast triangular trajectories in the X-axis, and a slow staircase trajectory in the Y-axis, while simultaneously achieving coupling compensation from the X-axis to Y-axis. The design and stability analysis of the MFRC scheme are presented in detail. The tracking results are experimen tally evaluated with a range of different load conditions, showing the efficacy of the method with large variations in plant dynamics. To address the coupling from the X-axis to the Y-axis while tracking the non-periodic staircase trajectories, a pre-learning step is used to generate the compensation signals, which is combined in a feedforward manner in real-time implementations. This approach is also applied to address the problem of longer convergence if needed. Experimental tracking control and coupling compensation is demonstrated on a commercially available piezoelectric-actuated scanner. The proposed method reduces the root-mean-square tracking from 191.4 nm in open loop or 194.6 nm with PI control, to 2.8 nm with PI+MFRC control at 100 Hz scan rate, which demonstrates the significant improvement achieved by the proposed method.},
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Martin-Jimenez, D.; Ruppert, M. G.; Ihle, A.; Ahles, S.; Wegner, H. A.; Schirmeisen, A.; Ebeling, D.
Chemical bond imaging using torsional and flexural higher eigenmodes of qPlus sensors Journal Article
In: Nanoscale - The Royal Society of Chemistry, vol. 14, no. 14, pp. 5251-5628, 2022.
@article{nokey,
title = {Chemical bond imaging using torsional and flexural higher eigenmodes of qPlus sensors},
author = {D. Martin-Jimenez and M. G. Ruppert and A. Ihle and S. Ahles and H. A. Wegner and A. Schirmeisen and D. Ebeling},
url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/04/Nanoscale-2022-Martin-Jimenez-bond-imaging-with-torsional-and-flexural-higher-eigenmodes.pdf},
doi = {10.1039/d2nr01062c},
year = {2022},
date = {2022-03-23},
urldate = {2022-03-23},
journal = {Nanoscale - The Royal Society of Chemistry},
volume = {14},
number = {14},
pages = {5251-5628},
abstract = {Non-contact atomic force microscopy (AFM) with CO-functionalized tips allows to visualize the chemical structure of adsorbed molecules and identify individual inter- and intramolecular bonds. This technique enables in-depth studies of on-surface reactions and self-assembly processes. Herein, we analyze the suitability of qPlus sensors, which are commonly used for such studies, for the application of modern multifrequency AFM techniques. Two different qPlus sensors were tested for submolecular resolution imaging via actuating torsional and flexural higher eigenmodes and via bimodal AFM. The torsional eigenmode of one of our sensors is perfectly suited for performing lateral force microscopy (LFM) with single bond resolution. The obtained LFM images agree well with images from the literature, which were scanned with customized qPlus sensors that were specifically designed for LFM. The advantage of using a torsional eigenmode is that the same molecule can be imaged either with a vertically or laterally oscillating tip without replacing the sensor simply by actuating a different eigenmode. Submolecular resolution is also achieved by actuating the 2nd flexural eigenmode of our second sensor. In this case, we observe particular contrast features that only appear in the AFM images of the 2nd flexural eigenmode but not for the fundamental eigenmode. With complementary laser Doppler vibrometry measurements and AFM simulations we can rationalize that these contrast features are caused by a diagonal (i.e. in-phase vertical and lateral) oscillation of the AFM tip.},
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Xavier, M. S.; Fleming, A. J.; Yong, Y. K.
Model-Based Nonlinear Feedback Controllers for Pressure Control of Soft Pneumatic Actuators Using On/Off Valves Journal Article
In: Frontiers in Robotics and AI, vol. 9, 2022, ISSN: 2296-9144.
@article{J22d,
title = {Model-Based Nonlinear Feedback Controllers for Pressure Control of Soft Pneumatic Actuators Using On/Off Valves},
author = {M. S. Xavier and A. J. Fleming and Y. K. Yong},
url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J22d.pdf},
doi = {10.3389/frobt.2022.818187},
issn = {2296-9144},
year = {2022},
date = {2022-03-17},
urldate = {2022-03-17},
journal = {Frontiers in Robotics and AI},
volume = {9},
abstract = {This article describes the application and comparison of three nonlinear feedback controllers for low-level control of soft actuators driven by a pressure source and single high-speed on/off solenoid valve. First, a mathematical model of the pneumatic system is established and the limitations of the open-loop system are evaluated. Next, a model of the pneumatic system is developed using Simscape Fluids to evaluate the performance of various control strategies. In this article, State-Dependent Riccati Equation control, sliding mode control, and feedback linearization are considered. To improve robustness to model uncertainties, the sliding mode and feedback linearization control strategies are augmented with integral action. The model of the pneumatic system is also used to develop a feedforward component, which is added to a PI controller with anti-windup. The simulation and experimental results demonstrate the effectiveness of the proposed controllers for pressure tracking.},
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Xavier, M. S.; Fleming, A. J.; Yong, Y. K.
Nonlinear Estimation and Control of Bending Soft Pneumatic Actuators Using Feedback Linearization and UKF Journal Article
In: IEEE/ASME Transactions on Mechatronics, vol. Early Access, 2022, ISBN: 1083-4435.
@article{J22e,
title = {Nonlinear Estimation and Control of Bending Soft Pneumatic Actuators Using Feedback Linearization and UKF },
author = {M. S. Xavier and A. J. Fleming and Y. K. Yong},
url = {https://www.precisionmechatronicslab.com/wp-content/uploads/2022/03/J22e-prepress.pdf},
doi = {10.1109/TMECH.2022.3155790},
isbn = {1083-4435},
year = {2022},
date = {2022-03-15},
urldate = {2022-03-15},
journal = {IEEE/ASME Transactions on Mechatronics},
volume = {Early Access},
abstract = {In this article, we combine nonlinear estimation and control methods for precise bending angle control in soft pneumatic actuators driven by a pressure source and single low-cost ON/OFF solenoid valve. First, a complete model for the soft actuator is derived, which includes both the motion and pressure dynamics. An unscented Kalman filter (UKF) is used to estimate the velocity state and filter noisy measurements from a pressure sensor and an embedded resistive flex sensor. Then, a feedback linearization approach is used with pole placement and linear quadratic regulator (LQR) controllers for bending angle control. To compensate for model uncertainties and improve reference tracking, integral action is incorporated to both controllers. The closed-loop performance of the nonlinear estimation and control approach is experimentally evaluated with a soft pneumatic network actuator. The simulation and experimental results show that the UKF provides accurate state estimation from noisy sensor measurements. The results demonstrate the effectiveness and robustness of the proposed observer-based nonlinear controllers for bending angle trajectory tracking.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
