Stretchable multifunctional sensor based on porous silver nanowire/silicone rubber conductive film

As one of the promising human–machine interfaces, wearable sensors play an important role in modern society, which advances the development of wearable fields, especially in the promising applications of electronic skin (e-skin), robotics, prosthetics, and healthcare. In the last decades, wearable sensors tend to be capable of attractive capabilities such as miniaturization, multifunction, and smart integration, and wearable properties such as lightweight, flexibility, stretchability, and conformability for wider applications. In this work, we developed a stretchable multifunctional sensor based on porous silver nanowire/silicone rubber conductive film (P-AgNW/SR). Its unique structural configuration, i.e., an assembly of the P-AgNW/SR with good conductivity, stability, and resistance response, and the insulated silicone rubber layer, provided the feasibility for realizing multiple sensing capabilities. Specifically, porous microstructures of the P-AgNW/SR made the device to be used for pressure sensing, exhibiting outstanding dynamic and static resistive responsive behaviors and having a maximum sensitivity of 9.062 %∙N⁻¹ in a continuous compressive force range of ~ 16 N. With the merit of the good piezoresistive property of AgNW/SR networks embedded into the surface of micropores of the P-AgNW/SR, the device was verified to be a temperature sensor for detecting temperature changes in the human body and environment. The temperature sensor had good sensitivity of 0.844 %∙°C⁻¹, high linearity of 0.999 in the range of 25–125 °C, and remarkable dynamic stability. Besides, the developed sensor was demonstrated to be a single electrode-triboelectric sensor for active sensing, owing to the unique assembly of the conductive P-AgNW/SR electrode and the silicone rubber friction layer. Based on the coupling effect of the triboelectrification and electrostatic induction, the generated electrical signals could be used to sense the human motions, according to the quantitative correlation between the human motions and the features in amplitude and waveform of the output signals. Thus, the developed stretchable sensor successfully achieved the integration of two types of passive sensing capabilities, i.e., pressure and temperature sensing, and one type of active sensing capability, i.e., triboelectric sensing, demonstrating the feasibility of monitoring multiple variables of the human body and environment.