Flexible Pressure and Temperature Microsensors for Textile-Integrated Wearables

Abstract

Environmental factors, such as pressure and temperature, are known to contribute to the formation of ulcers that seriously affect bedridden individuals. Researchers have proposed several technologies to achieve the long-term monitoring of those parameters, usually relying on sensing mats, which poses difficulties in correlating the measurements with specific parts of the body. In this work, we aim to develop microsensors to be integrated into patient clothing. They should be highly flexible, thin with a small footprint, and can be achieved by taking advantage of the microfabrication on polyimide (PI) thin-film substrates (total device thicknesses below 30 µm). Both resistive and capacitance transduction mechanisms were explored, targeting operation ranges of 1 to 40 kPa and 24 to 42 °C. The sensors were integrated into textiles using silicone elastomers and electrical connections based on conductive silver yarn. The experimental characterization showed a nominal capacitance of 21 pF, a sensitivity of −8.44 fF/kPa for the pressure sensors, and a 0.0021 Ω/Ω°C sensitivity of the temperature sensor (with resistance of 29 kΩ at 22 °C). The proposed approach can potentially be implemented not only in wearable devices but also in many other applications for health monitoring or human–machine interfaces.