Investigation of Polymer Micro-Actuators Based on Electrostrictive Poly(vinylidene fluoride-trifluoroethylene) Copolymer
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Investigation of Polymer Micro-Actuators Based on Electrostrictive Poly(vinylidene fluoride-trifluoroethylene) Copolymers Tian-bing Xu1, Feng Xia, Z.-Y. Cheng, and Q. M. Zhang Materials Research Institute and Department of Electrical Engineering The Pennsylvania State University, University Park, PA 16802 1 NASA/LaRC, Hampton, VA 23681 ABSTRACT Micromachined actuators based on the electrostrictive P(VDF-TrFE) copolymer, which possesses a high strain (~5%) and high elastic energy density (~ 1 J/cm3), have been designed and fabricated. The performance of the devices have been characterized and modeled in terms of the properties of the copolymer and dimensions of the devices. The experimental results on the device responses under high AC fields (electrostrictive mode), weak AC fields in DC field biased state, and frequency dependence, are very close to the modeling results. Due to the large field induced strain and high frequency capability of the electrostrictive P(VDF-TrFE), the device possesses the capability of operation at non-resonance mode with high displacement and force output, and hence, the device is capable to be used over a broad frequency range. For example, for a device of 1 mm lateral dimension, the displacement output can reach more than 50 µm and the ratio of the displacement/applied voltage is more than 20 nm/Vrms. Furthermore, over more than 3 frequency decades (up to 100 kHz), the dispersion of the displacement is less than 20%. The observed performance of the devices indicates that this class of the electrostrictive P(VDF-TrFE) based micro-actuators is attractive for micropumps and valves. INTRODUCTION BioMEMs represents a promising new direction in meeting 21st century health care challenges. BioMEMs integrate microscale sensors, actuators, microfluidics, micro-optics, and structural elements with computation, communications and controls for application to medicine for the improvement of human health. Derived from the microfabrication technology used to make integrated circuits, BioMEMs is expected to revolutionize the way medicine is practiced and delivered. The ability to apply batch fabrication methods to the manufacture of BioMEMs might also enable greater accessibility to medical procedures through a lower overall cost of health care delivery [1]. A concept of a miniaturized total analysis system (µTAS) has been developed in recent years [2]. Ideally, a µTAS performs all the component stages of a complete analysis in an integrated and automated fashion. Typically, a µTAS is a microchip or microdevice fabricated using conventional micromaching technologies, such as BioMEMs technology is used in µTAS system. A µTAS needs the fabrication of micro-components for fluid handing, such as microvalves, micropumps, microsensors and microchannels, and proper system integration. More recently, polymer or plastics based µTAS and microfluidic devices have gained more attentions due to the lost cost, ease of mass production and biocompatibility of the polymeric materials [3]. The viability of µTAS
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