Transparent, multifunctional and multiform ionic sensors prepared by one-step impregnation

Under current technology trends, wearable devices with high levels of transparency and flexibility have become hotspots to improve aesthetics or enhance security for civilian and military applications. Simultaneously, the single sensor can no longer satisfy the various needs, like temperature and humidity, stress and strain and so on. However, it is still challenging that how to fabricate multifunctional transparent sensors nowadays. In this paper, the transparent polyurethane (PU) film was easily prepared by impregnating the ionic liquid (IL) into the pure PU film (PU@IL). And the effects of film thickness, ionic concentration and fiber morphology on transparency are investigated by experiments and simulations. On the basis of it, several sensors based on PU@IL film are further developed. The resistive sensor with PU@IL film shows different sensing abilities for stress, strain and temperature. Capacitive sensor based on indium tin oxide (ITO)-PU@IL-ITO has a lower stress detection limit (0.51 kPa) and faster response/recovery time (136.8 ms/68.4 ms). This paper may provide a novel strategy to design and fabricate multifunctional and multiform sensors with good mechanical properties, transparency and wide applications (preventing scalds, monitoring physiological activities).