Frequency-dependent electrostatic actuation in microfluidic MEMS

Sounart, Thomas L.; Michalské, Terry A.; Zavadil, Kevin R.

doi:10.1109/jmems.2004.839006

Cited by 109 publications

(136 citation statements)

References 34 publications

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“…To date, KPFM has been implemented in liquid in the absence of ions (nonpolar liquid) 20 and limited progress has been obtained in low-molarity electrolytes (o10 mM) using KPFM modes, which do not require bias feedback (for example, open-loop KPFM) 21,22 . While electrostatic forces are increasingly being used to actuate atomic force microscope (AFM) cantilever motion in liquids to measure surface topography [23][24][25][26] , surface charge density 26 and dielectric constants [27][28][29] , voltage-modulated (VM) SPM imaging in conductive electrolytes presents an unresolved challenge.…”

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confidence: 99%

Probing charge screening dynamics and electrochemical processes at the solid–liquid interface with electrochemical force microscopy

et al. 2014

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The presence of mobile ions complicates the implementation of voltage-modulated scanning probe microscopy techniques such as Kelvin probe force microscopy (KPFM). Overcoming this technical hurdle, however, provides a unique opportunity to probe ion dynamics and electrochemical processes in liquid environments and the possibility to unravel the underlying mechanisms behind important processes at the solid-liquid interface, including adsorption, electron transfer and electrocatalysis. Here we describe the development and implementation of electrochemical force microscopy (EcFM) to probe local bias-and time-resolved ion dynamics and electrochemical processes at the solid-liquid interface. Using EcFM, we demonstrate contact potential difference measurements, consistent with the principles of open-loop KPFM operation. We also demonstrate that EcFM can be used to investigate charge screening mechanisms and electrochemical reactions in the probe-sample junction. We further establish EcFM as a force-based imaging mode, allowing visualization of the spatial variability of sample-dependent local electrochemical properties.

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confidence: 99%

Probing charge screening dynamics and electrochemical processes at the solid–liquid interface with electrochemical force microscopy

et al. 2014

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“…1 Recently it has been shown that the stable actuation range can be extended by adding an electret layer to the gap 2 or by operating in a high-dielectric fluid medium with relatively thick low-dielectric solid insulating layers on the electrodes. 3,4 Electrostatic actuation in highdielectric media requires ac drive signals at frequencies f at least on the order of the critical actuation frequency f c to prevent electrode polarization and electrolysis, [5][6][7] but offers the advantage of lower actuation voltages, and is particularly important to microfluidic and bioMEMS development where it is desirable to integrate actuators into aqueous solutions and other conductive fluids. [8][9][10][11][12] For simplicity and to minimize the applied potential required for actuation, most applications of electrostatic actuators in conductive media have been operated in the high frequency limit, viz.,…”

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confidence: 99%

“…The impedance of the electrical double-layer in the gap is typically much lower than that of the passivation layers on microactuator devices, and thus can be neglected. 6 Thus for negligible resistance of the bulk electrode relative to the fluid in the gap, the actuator can be accurately represented by the RC circuit also in Fig. 1.…”

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confidence: 99%

Frequency-dependent stability of parallel-plate electrostatic actuators in conductive fluids

Sounart

Panchawagh

Mahajan

2010

Applied Physics Letters

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We present an electromechanical stability analysis of passivated parallel-plate electrostatic actuators in conductive dielectric media and show that the pull-in instability can be eliminated by tuning the applied frequency below a design-dependent stability limit. A partial instability region is also obtained, where the actuator jumps from the pull-in displacement to another stable position within the gap. The results predict that the stability limit is always greater than the critical actuation frequency, and therefore any device that is feasible to actuate in a conductive fluid can be operated with stability over the full range of motion.

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“…This could also lead to higher bandwidth recording for dynamic measurements or integration with patch clamp recordings. Other advances like the development of microactuators in liquid media also have potential applications in controlled application of forces to study cell mechanics (83). New techniques are also being developed that could bridge the gap between IC-based devices and soft-polymer devices.…”

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confidence: 99%

Microsystems for Biomechanical Measurements

et al. 2008

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ABSTRACT:The use of microtechnology to make biomechanical measurements allows for the study of cellular and subcellular scale mechanical forces. Forces generated by cells are in the few nanoNewton to several microNewton range and can change spatially over subcellular size scales. Transducing forces at such small size and force scales is a challenging task. Methods of microfabrication developed in the integrated circuit industry have allowed researchers to build platforms with cellular and subcellular scale parts with which individual cells can interact. These parts act as transducers of stresses and forces generated by the cell during migration or in the maintenance of physical equilibrium. Due to the size and sensitivity of such devices, quantitative studies of single cell and even single molecule biomechanics have become possible. In this review we focus on two classes of cellular force transducers: silicon-based devices and softpolymer platforms. We concentrate on the biomechanical discoveries made with these devices and less so on the engineering behind their development because this is covered in great detail elsewhere.

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Frequency-dependent electrostatic actuation in microfluidic MEMS

Cited by 109 publications

References 34 publications

Probing charge screening dynamics and electrochemical processes at the solid–liquid interface with electrochemical force microscopy

Probing charge screening dynamics and electrochemical processes at the solid–liquid interface with electrochemical force microscopy

Frequency-dependent stability of parallel-plate electrostatic actuators in conductive fluids

Microsystems for Biomechanical Measurements

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