HIGH PERFORMANCE MICROMACHINED TRANSDUCER BASED ON ELECTROSTRICTIVE P(VDF-TrFE) POLYMER Tian-Bing Xu and Q.M. Zhang Materials Research Institute and Electrical Engineering Department The Pennsylvania State University, University Park, PA 16802 Abstract: High performances of micromachined unimorph actuators (polymer micro-macnined actuator or PMAT) based on the electrostrictive poly(vinylidede fluoride-trifluoroethylene) (P(VDF- TrFE)) copolymer is developed. The PMAT exhibits a very high stroke level with high load capability, broad frequency range (>100kHz), and high displacement sensitivity. In addition, the simulated results, based on the properties of the materials and the structure of the device, are consisting with the experimental observation. I. INTRODUCTION Micro-electro-mechanical systems (MEMS) have shown great potential and impact on a broad range of modern technologies such as biotechnology, optical communications, automobiles, and many other domestic and military applications. 1-4 Micro-actuator is the key component in MEMS. However, in spite of more than a decade efforts, it is still a challenge to realize micro-actuators capable of operating over a broad frequency range with high force level and large displacement output. 5-8 The fundamental reason behind this is the lacking in the present active material or actuation mechanism which possesses high elastic energy density with high strain capability over a broad frequency range. Recently, we reported that in modified P(VDF-TrFE) polymers, a massive electrostriction with high elastic energy density can be achieved. 9-12 Especially, in uniaxially stretched polymer samples, an electrostrictive strain larger than 3.5% with high load capability (~40 MPa) along the film surface and stretching direction has been demonstrated which makes the polymer attractive for micro-actuators. 10,11 It is the purpose of this article to investigate the micro-actuator device performance of this new class of active polymer (polymer micro- actuator, or PMAT). II. DEVICE STRUCTURE AND OPERATION PRINCIPLE The PMAT configuration adopted for this investigation is shown schematically in figure 1. The active polymer, which is a film (~10 m thickness) of Figure 1. (a) Schematic of the PMAT investigated. (b) The electrode pattern of the PMAT active polymer (black area) where the electrode width along the x-direction is the same as the device actuation length L 0 in the same direction and along the y-direction, the unelectroded margin width is 0.5 mm to prevent the breakdown at the edges. (c) Schematic of the actuation response of the current PMAT under external fields: because of S 1 >0, the actuator moves up L 0 Substrate Active polymer Inactive polymer Epoxy Electrodes Polymer stretching direction Si3N4 SiO2 Si Z (a) L0 W Polymer stretching direction (b) Y X (c) L 0 Z X 2001 IEEE ULTRASONICS SYMPOSIUM-917 0-7803-7177-1/01/$10.00 © 2001 IEEE