Fabrication of CNT-based MEMS piezoresistive pressure sensors using DEP nanoassembly

This paper reports the fabrication technique of a novel carbon nanotubes (CNTs) based MEMS pressure sensor with piezoresistive gauge factor potentially much greater than polysilicon based sensors. By using the dielectrophoretic (DEP) nanoassembly of CNTs and a MEMS-compatible process, we have successfully integrated bundled strands of CNT sensing elements on arrays of polymethylmethacrylate (PMMA) diaphragms. The piezoresistive effects of CNT were preliminarily investigated by measuring the pressure-resistance dependency of the sensors and preliminary results indicated that the CNT-based microsensors were capable of sensing input pressure variations. Moreover, the mechanical properties of the diaphragms were studied experimentally and theoretically, which showed the deflection and strain distribution of the diaphragms with different input pressures, in order to conclusively determine the piezoresistivity of bundled CNTs. Based on these experimental evidences, we propose that carbon nanotubes is a novel material for fabricating micropressure sensors on polymer substrates-which may serve as alternative sensors for silicon based pressure sensors when biocompatibility and low-cost applications arc required.