A PMMA-based micro pressure sensor chip using carbon nanotubes as sensing elements

A polymer-based MEMS pressure sensor was fabricated using bulk multi-walled carbon nanotube (MWNT) as piezoresistive sensing elements. The development of the pressure sensor includes fabrication of 300/spl mu/m thick polymethylmethacrylate (PMMA) diaphragms using SU8 molding/hot-embossing technique and AC electrophoretic manipulation of MWNT bundles on the diaphragms. We have measured the pressure-resistance dependency of these MWNT-based micro sensors and preliminary results indicated that the MWNT sensors were capable of sensing input pressure variations. Moreover, the I-V measurements of the resulting devices revealed that the nominal resistance of the sensing elements can be adjusted by annealing the MWNTs through electrical current heating, which offers a potential method for resistance-off set calibration. Based on these experimental evidences, we propose that carbon nanotubes (CNTs) is a novel material for fabricating micro pressure sensors on polymer substrates - which may serve as alternative sensors for silicon based pressure sensors when bio-compatibility and low-cost applications are required.