Surface Modification of Super Arborized Silica for Flexible and Wearable Ultrafast‐Response Strain Sensors with Low Hysteresis

Abstract

Abstract Conductive hydrogels exhibit high potential in the fields of wearable sensors, healthcare monitoring, and e‐skins. However, it remains a huge challenge to integrate high elasticity, low hysteresis, and excellent stretch‐ability in physical crosslinking hydrogels. This study reports the synthesis of polyacrylamide (PAM)‐3‐(trimethoxysilyl) propyl methacrylate‐grafted super arborized silica nanoparticle (TSASN)‐lithium chloride (LiCl) hydrogel sensors with high elasticity, low hysteresis, and excellent electrical conductivity. The introduction of TSASN enhances the mechanical strength and reversible resilience of the PAM‐TSASN‐LiCl hydrogels by chain entanglement and interfacial chemical bonding, and provides stress‐transfer centers for external‐force diffusion. These hydrogels show outstanding mechanical strength (a tensile stress of 80–120 kPa, elongation at break of 900‐1400%, and dissipated energy of 0.8–9.6 kJ m−3), and can withstand multiple mechanical cycles. LiCl addition enables the PAM‐TSASN‐LiCl hydrogels to exhibit excellent electrical properties with an outstanding sensing performance (gauge factor = 4.5), with rapid response (210 ms) within a wide strain‐sensing range (1–800%). These PAM‐TSASN‐LiCl hydrogel sensors can detect various human‐body movements for prolonged durations of time, and generate stable and reliable output signals. The hydrogels fabricated with high stretch‐ability, low hysteresis, and reversible resilience, can be used as flexible wearable sensors.

Keywords

• low hysteresis
• nanocomposite conductive hydrogels
• strain sensors
• super arborized silica