Wearable and antibacterial HPMC-anchored conductive polymer composite strain sensor with high gauge factors under small strains

Recently, with the increasing demand for health services, wearable devices have attracted a wide range of researchers' interests. Flexible polymer composites are widely concerned for their unique mechanical property and machinability. However, both the conductivity and mechanical properties of conductive polymer composites (CPCs) prepared by direct doping are affected by the conductive nanofillers. Additionally, the selective modifications of conductive fillers on polymer substrate surface have been criticized for their instability. To tackle this, we propose a multifunctional conductive polymer composite (M-CPC) with great flexibility, high conductivity, and antibacterial property, consisting of thermoplastic polyurethane (TPU) and synthetic silver nanoflowers (AgNF), which are embedded by hydroxypropyl methyl cellulose (HPMC). Actually, HPMC can achieve the excellent dispersibility of AgNF and establish a strong contacting between TPU substrate and HPMC/AgNF conductive film through hydrogen bonds. The M-CPC (TPU/HPMC/AgNF) exhibits high conductivity and cyclical stability. Further, the HPMC dispersed AgNF conductive network endows M-CPC with superior strain sensing performance, possessing an extremely high gauge factor (GF) of 2.8 x 10(7) (working strain: 30-35%), which is the highest GF of CPCs under small strains and has never been reported before. Additionally, HPMC/AgNF also makes M-CPC antibacterial, which has a relatively long-term antibacterial effect for 3 days.