Photothermally actuated Ti₃C₂T_x MXene-GO resonator for highly sensitive humidity sensing

In order to achieve high sensitivity in a wide measurement range for miniature humidity sensing, we developed an optical-fiber Fabry-Perot (F–P) interferometric resonant humidity sensor using a Ti₃C₂T_x MXene-graphene oxide (GO) composite membrane (125 μm in diameter and ∼0.61 μm in thickness) with a MXene:GO mass ratio of 2.5:1. The suspended MXene-GO composite membrane was photothermally excited to vibrate using an intensity-modulated laser, with its vibration detected via non-contact optical fiber F–P interferometric readout. Over 2∼100%RH at 25 ℃, the sensor achieves an absolute sensitivity of 2.1 kHz/%RH, corresponding to a relative sensitivity of 0.22%/%RH that is higher than those obtained by previously reported quartz crystal microbalance (QCM), surface acoustic wave (SAW), and film bulk acoustic resonator (FBAR)-based humidity sensors typically ranging from 8.4 × 10⁻⁵ to 1.89 × 10⁻³%/%RH. Additionally, the sensor exhibited good repeatability (2.57%), hysteresis error (6.11%), fast response/recovery time (3.61 s/5.53 s) and a maximum frequency deviation of 0.27% at 76%RH in the two-week stability test.