Design, fabrication, and characterization of SU-8/carbon black nanocomposite based polymer MEMS acceleration sensor

Abstract

Design, fabrication, and characterization of SU-8/carbon black (CB) nanocomposite based single axis acceleration sensor is presented. The entire sensor made of SU-8 photosensitive polymer is fabricated using the process spin pattern anchor release device. Thanks to the low young’s modulus of SU-8 polymer, the cantilever beams used to support the proof mass are very flexible, which resulted in increased sensitivity. A composite layer of CB nanoparticles mixed with the SU-8 polymer is sandwiched between two SU-8 2002 layers in the cantilever beam. This nanocomposite layer acts as a piezoresistive layer and is used to measure the induced stress and strain. The piezoresistors are patterned in a full bridge Wheatstone arrangement to cancel the effect on temperature variation. Maximum stress locations are identified through Finite Element -Modeling based simulations under accelerations up to 100 g. The natural frequency, stiffness, and sensitivity of the acceleration sensor are characterized using the techniques of nanoindenter and Laser Doppler Vibrometer. The measured natural frequency is 1.884 kHz. The relative change in resistance per unit strain of the prototype is measured using I–V measurements, which gives a gauge factor of 13.05.