Highly breathable and stretchable strain sensors based on porous films for human motion and gas detection

With the rapid development of flexible wearable sensors in the fields of medical detection and environmental monitoring, it is urgent to develop multifunctional sensors with high sensitivity, fast response, wide sensing range, excellent comfort and multi-stimulus response. In this paper, a porous thermoplastic polyurethane (TPU) film with high stretchability and breathability was prepared by facial liquid phase separation, and a flexible wearable sensor was developed through vapor deposition of polypyrrole (PPy) within the porous TPU film matrix. The fabricated sensor can detect pressure, strain and gas, has a wide pressure detection range (up to 98 kPa), fast response speed (100 ms), sensitivity of up to 0.33 kPa⁻¹ and working stability. Furthermore, it has an extremely high tensile strength of 790 % and can operate in the 0–400 % stretch range with a maximum sensitivity of 238.2. Importantly, the flexible porous TPU/PPy multifunctional sensor has excellent breathability and the capability to monitor NH₃ gas, and the gas detection limit can reach 10 ppm. This work provides a new route for achieving high-performance and wearing comfortable strain sensors with broad application prospects in human activity detection and NH₃ gas monitoring devices.