Projects

@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}

}

@article{Yong2016b,

title = {A new preload mechanism for a high-speed piezoelectric stack nanopositioner},

author = {Y. K. Yong},

url = {http://www.eng.newcastle.edu.au/~yy582/Papers/Yong2016_preload.pdf},

year  = {2016},

date = {2016-04-13},

journal = {Mechatronics},

volume = {36},

pages = {159-166},

abstract = {Piezoelectric stack actuators are the actuator of choice for many ultra-high precision systems owning to its fast responses and high pushing force capabilities. These actuators are constructed by bonding multiple piezoelectric layers together. An inevitable drawback of these actuators is that there are highly intolerant to tensile and shear forces. During high-speed operations, inertial forces due to effective mass of the system cause the actuators to experience excessive tensile forces. To avoid damage to the actuators, preload must be applied to compensate for these forces. In many nanopositioning systems, flexures are used to provide preload to the piezoelectric stack actuators. However, for high-speed systems with stiff flexures, displacing the flexures and sliding the actuators in place to preload them is a difficult task. One may reduce the stiffness of the flexures to make the preload process more feasible; however, this reduces the mechanical bandwidth of the system. This paper presents a novel preload mechanism that tackles the limitations mentioned above. The preload stage, which is connected in parallel mechanically to a high-speed vertical nanopositioner, allows the piezoelectric stack actuator to be installed and preloaded easily without significantly trading of the stiffness and speed of the nanopositioning system. The proposed vertical nanopositioner has a travel range of 10.6 μ m. Its first resonant mode appears at about 24 kHz along

the actuation direction.},

keywords = {},

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 = {},

pubstate = {published},

tppubtype = {article}

}