Thin‐Film Thermal Sensors on Chitosan Substrates for Sustainable Transient Electronics

ABSTRACT In recent years, transient (bio)electronics has witnessed a remarkable surge for their potential in sustainable and biocompatible electronic solutions. Here, chitosan‐based films are demonstrated as versatile transient substrates for thin‐film thermal sensors, merging sustainability with standard microfabrication. Two sensor types are fabricated: resistive temperature detectors (RTDs) via sputtering of a 100 nm molybdenum (Mo) layer, and thermistors through subsequent deposition of a 50 nm amorphous indium gallium zinc oxide (a‐IGZO) semiconductor layer. Bi‐directional thermal characterization in physiologically relevant ranges (25–55 , 2.0% RH) reveals that both device types exhibited linear and reproducible responses. The thermistors show a significantly higher sensitivity (0.0184 ) more than an order of magnitude greater than the RTDs (0.0010 ), with minimal deviation during extended thermal cycling (standard deviations 0.016 and 0.0006, respectively). The sensors maintain full functionality under severe mechanical deformation, including twisting, folding, and bending to radii as small as 8 mm. Importantly, the devices are fully transient, dissolving completely in aqueous and mildly acidic environments within approximately 50 hours. This work establishes chitosan‐based substrates as a promising platform for functional transient electronics leveraging existing thin‐film technologies, paving the way for sustainable applications in soft robotics, agritech, and healthcare.