Humidity sensor of tunnel-cracked nickel@polyurethane sponge for respiratory and perspiration sensing

ABSTRACT High-performance humidity sensors with a porous structure have attracted tremendous attention in recent years. Following the bionics principle of spider's legs, we propose a novel humidity sensor based on a tunnel-cracked nickel@polyurethane sponge (TCNi@PUS) fabricated by ion beam sputtering deposition and mechanical compression methods in which nano-cracked conductive network are formed on PUS skeletons. The TCNi@PUS sensors exhibit a resistance-humidity response over wide humidity range of 10 ∼ 95%RH with good linearity and tunable sensitivity, fast response/recovery times of 0.8 s/3.6 s, superior repeatability and long-term stability. The mechanism underlying the tunable humid sensitivity of the TCNi@PUS sensors is based on adjusting the width of the tunnel cracks for conductive metal and the hygroscopic swelling rate for polymer. On the basis of this superior sensing performance, it is successfully demonstrated that TCNi@PUS sensors can be applied for real-time healthcare and activities monitoring.