Parametrically Amplified Low-Power MEMS Capacitive Humidity Sensor

TL;DR

This paper introduces a polymer-based MEMS humidity sensor utilizing parametric amplification to significantly enhance response signal, achieving high sensitivity and fast response with low power consumption.

Contribution

The work presents a novel MEMS humidity sensor design that employs parametric amplification for improved signal strength and sensitivity without traditional electronic amplifiers.

Findings

11-fold increase in sensor response due to parametric amplification

Capacitance change of 11% for 25-85% humidity variation

Response time approximately 1 second

Abstract

We present the design, fabrication, and response of a polymer-based Laterally Amplified Chemo-Mechanical (LACM) humidity sensor based on mechanical leveraging and parametric amplification. The device consists of a sense cantilever asymmetrically patterned with a polymer and flanked by two stationary electrodes on the sides. When exposed to a humidity change, the polymer swells after absorbing the analyte and causes the central cantilever to bend laterally towards one side, causing a change in the measured capacitance. The device features an intrinsic gain due to parametric amplification resulting in an enhanced signal-to-noise ratio (SNR). 11-fold magnification in sensor response was observed via voltage biasing of the side electrodes without the use of conventional electronic amplifiers. The sensor showed a repeatable and recoverable capacitance change of 11% when exposed to a change in relative humidity from 25-85%. The dynamic characterization of the device also revealed a response time ~1s and demonstrated a competitive response with respect to a commercially available reference chip.