Responsible Humidity Sensor by Direct Laser Writing on Cork Substrate

Abstract A novel laser‐induced graphene (LIG) resistive relative humidity (RH) sensor is successfully fabricated by direct laser writing on a common natural cork sheet. In this work, a straightforward fabrication is presented where LIG, porous multilayer graphene, is generated by a laser photothermal process on a carbon‐based substrate, in this case, an agglomerate cork sheet. The formation of LIG material is revealed by structural and morphological characterization using various analyses, including Raman spectroscopy, X‐ray Photoelectron spectroscopy (XPS), and Scanning Electron Microscopy (SEM). The electrical analyses are conducted to measure the resulting sheet resistance, getting results as low as 31 Ω sq⁻¹. With the laser parameter optimized, a LIG resistive humidity transducer is manufactured and characterized in a climate chamber. This biodegradable sensor shows good linearity with a sensitivity of 0.015%/%RH from 40 to 80% RH. Additionally, the influence of temperature is studied and demonstrated a low impact on the sensor's response toward RH. Furthermore, a proof of concept is successfully implemented by integrating the transducer onto a cork stopper. Considering all, the prospect of creating an easy, fast, scalable, and cost‐effective transducer combined with the use of natural and abundant materials, leads the way for future large‐scale production of sustainable sensors.