Inorganic Nanowires Based Stretchable Sensors for Wearable Applications

Robust stretchable sensors (temperature, strain, optical, pressure etc.) are the critical components of wearable electronic systems health monitoring and wellness applications. In these applications the sensors are expected to show stable performance under bending, stretching and other mechanical loading conditions. While commonly explored organic and inorganic-organic hybrid materials based sensors meet these requirements, their modest performance (e.g., mobility, conductivity) and stability hinder their wider use. In this regard, the inorganic semiconductors nanowires (NWs), 2D materials, metallic NWs etc. are attractive owing to their distinct physical and chemical properties. Further, inorganic semiconductors based flexible/stretchable sensors can be developed using novel transfer/printing techniques. The current work demonstrates inorganic metallic and semiconducting NWs based stretchable strain sensors and photodetectors (PDs) on Ecoflux substrate with stable performance under high cyclic loading conditions. The functional components of both the strain and UV sensors are based on inorganic nanomaterials on an eco-friendly substrate. Silver (Ag) NWs have been used to fabricate stretchable strain sensor that displayed good linearity in the low strain range (< 40%), high cyclic stability beyond 5000 and fast response time (~200 ms). The sensor has been integrated over human finger to evaluate the bending strain for applications in smart gloves and robotics. The fabrication methodology has been extended to develop a ZnO NWs based stretchable UV dosage monitor for human skin health monitoring applications. The UV sensing device configured as metal-semiconductor-metal structure on Ecoflux substrate displayed stable performance over 10,000 cycles. The sensor exhibited good characteristics of responsivity (77 A/W), and detectivity (6.6 x 10¹³ jones) for UV light, at par or better than common organic and hybrid stretchable PDs.