Multi-functional resonant micro-sensor for simultaneous magnetic, CO₂, and CH₄detection

We present a highly sensitive multi-parameter sensor for magnetic and gas detection. The device is based on an in-plane doubly clamped micro-beam micro-resonator, which is electrothermally heated. It acts as a Lorentz force magnetic sensor of high sensitivity, good linearity, good repeatability, and low hysteresis effect. It also functions as a gas-sensor based on the cooling/heating effect of the micro-beam as demonstrated for carbon dioxide (CO2) and methane (CH4) detection. The CO2/CH4 sensor shows high sensitivity and excellent linearity. In addition, we demonstrate simultaneous magnetic and gas detection by tracking the frequency shift of the first two symmetric and anti-symmetric modes at the same time. We show that the sensitivity of the magnetometer is gas-independent and only depends on the frequency shift of the second mode, which is unaffected by variations of the thermal axial load. For the first time, high sensitivity to magnetic fields, CO2, and CH4 is demonstrated using the same device. The demonstrated simultaneous and highly-sensitive multi-parameter sensing platform using a single resonator is promising for smart environmental and monitoring applications.