MEMS Piezoresistive Pressure Sensor On Flexible Substrates Using Nichrome And CNT/polyimide Nanocomposites Piezoresistors

Abstract

Micro pressure sensors using nichrome as piezoresistor were fabricated on silicon and flexible substrates. The pressure sensors on flexible substrate can be used for prosthetic skin applications. The devices were successfully tested using different methods.Micromachined pressure/force sensors using nickel chromium piezoresistors have been investigated experimentally and through finite element mesh analysis. The pressure/force sensors were designed using a suspended aluminum oxide membrane with optimally placed piezoresistors to measure the strain in the membrane when deflected with an applied force or pressure. Different devices, each with varying size and shape of both the membrane and the piezoresistors were designed, fabricated, and characterized. The piezoresistors were placed into a Wheatstone bridge configuration with two active and two passive nickel chromium resistors to provide temperature drift compensation. The measured results showed a 12% maximum change in resistance when the membrane is fully deflected from its original position due to the application of an applied load. Finally Gauge factor for thin film nichrome was found out using the combination of experimental and simulation results. Nanocomposites using CNT and polyimide were developed for pressure sensing application which can be deposited using spin-coat method. Electrically conductive CNT/polyimide nanocomposites were achieved after depositing on the wafer using spin-coat method by varying the concentration of CNTs and polyimide. The deposited CNT/polyimide nanocomposite was patterned using the combination of RIE as well as liftoff technique to form the piezoresistive structure on top of the aluminum oxide membrane. The micro pressure sensor using CNT/polyimide nanocomposites as piezoresistor was fabricated and the individual resistance of the piezoresistor across Wheatstone bridge network was measured.