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Fabrication and demonstration of the first all-polymer microresonators
All-polymer microbridge electrostatic actuators based on a blended conductive polymer (PMMA and PEDOT/PSS) are fabricated using surface micromachining on glass substrates. A fabrication process is developed that allows the preservation of the electrical conductivity of the polymer structural layer and the suspension of the polymer microbridges. The electromechanical properties of the microbridges are studied using electrostatic actuation and optical and electrical detection. The pull-in phenomena and a dependence of the bridge deflection with the square of the applied voltage are observed. Compared to the silicon-based microbridges, the polymer structures present higher deflection amplitude for the same applied electrical force. The resonance frequency of the polymer bridges occurs in the MHz range with quality factors of the order of 100 when measured in vacuum. The mechanical properties of the polymer device are affected by residual stress.
All-polymer resonator microbridges with a structural layer composed of a bilayer of the blended conductive polymer and a polyimide (PI) layer are also fabricated. In this bilayer structure, the conducting polymer layer allows electrostatic actuation, and the second polymer layer is chosen to provide the mechanical, optical or chemical properties of the microstructure, thus significantly increasing the range of properties available for the MEMS structural layer.
All-polymer MEMS fabricated by surface micromachining using PMMA blended with a conductive polymer. On the right, the resonance frequencies of the polymer MEMS.