Harsh environment-tolerant and robust superhydrophobic graphene-based composite membrane for wearable strain sensor

The sensing stability of strain sensors in complex environments (e.g., humidity, raindrops) is limited by the influence of water molecules on their sensor performance. Equipping strain sensors with superhydrophobicity is a promising strategy to address this issue. In this work, a harsh environment-tolerant and robust super-hydrophobic flexible graphene-based composite membrane (GCM/TPU/SiC/PFOTS-SFGCM) was fabricated via a convenient blending method and subsequent spraying method, in which thermoplastic polyurethane (TPU) was used as the matrix and chemically modified reduced graphene oxide as the conductive filler, GCM was prepared by a simple mixing process, and the mixed solution of TPU, SiC nanoparticles, and Perfluoroalkyltriethoxysilanes (PFOTS) was sprayed on the surface of GCM to prepare SFGCM. The SiC micro-nano particles in the middle layer form a rough structure, the TPU layer combines the loose SiC micro-nano particles together, and the PFOTS layer further combines the SiC nanoparticles to play a low surface energy role. This SFGCM has good super-hydrophobicity with a water contact angle of 164 degrees and excellent conductivity with a conductivity of 4.5 x 104 S/ m. After being subjected to harsh environments, its superhydrophobicity, conductivity and ability to collect continuous signals may be nearly maintained. The SFGCM has a response time of 471.03 ms, a recovery time of 865.05 ms and a sensitivity of 141.4 under a 20% strain ratio, and a 113.1 m/min stretching speed. It may also be assembled as electronic skin to detect human body movements (such as the finger, wrist, and elbow), making it a suitable option for wearable electronics. This research paves the way for multifunctional wearable sensors that can provide fast response, long-term reliability and broad applications in harsh environments.