Thick High Aspect-Ratio Biomimetic Silicon Hair Sensors as Accelerometers

Abstract

In nature, hair typically exists in large-scale arrays, offering improved sensitivity and dynamic range. In this paper, we present a new high aspect-ratio (HAR) hair biomimetic microstructure used as an accelerometer and it consists of a vertically anchored hair-like spring with a proof-mass attached to the top of it and made from thick silicon. Silicon structures mimicking hair, fabricated by MEMS technology, have the potential to greatly improve sensor performance by combining large and dense arrays of HAR microstructures with efficient transduction mechanisms and local interface circuits. Signal processing of the MEMS array outputs (hundreds or thousands) can eventually provide multiplicity of functions, including high sensitivity, greater dynamic range, reduced parasitics, fault-tolerance, and reconfigurability. We present a thick silicon capacitive MEMS accelerometer and accelerometer arrays with a small-footprint based on this microstructure. Multiple electrodes surrounding the core hair structure form differential capacitive pairs and enable fully symmetric readout as well as force-feedback closed-loop operation for sensing acceleration. Arrays of 64 accelerometers each with a footprint of 200 × 200 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and 500 μm thick have been demonstrated.