Waterproof strain sensor based on superhydrophobic, conductive carbon-coated tussah silk for human motion detection under hydrated environment

Abstract

Conductive silk-based composites, prepared via surface modification techniques, have found extensive applications in wearable sensor technologies due to their excellent bio-compatibility and mechanical toughness. However, there is a critical limitation of traditional silk-based strain sensors that failing under hydrated conditions. Herein, we developed a waterproof strain sensor based on superhydrophobic and conductive tussah silk (SCTS) via a facile coating strategy that synergistically combined the carbon composite (one-dimensional hydrophobic MWCNTs, zero-dimensional hydrophobic CB, and TPU) with silk skeleton. The coating exhibited unprecedented mechanical robustness, the superhydrophobicity maintained stable even after stretching cycles (50 % strain), impacts, hand-kneading, and sandpaper abrasion, attributed to elasticity and strong adhesion of the TPU. Additionally, the SCTS sensor demonstrated exceptional strain sensing capabilities, featuring a wide sensing range (up to 120 % strain), high sensitivity (GF of 7.52), and superior cyclic stability (exceeding 500 cycles at 20 % strain). Owing to these merits, this wearable sensor was successfully applied for monitoring human motions under hydrated environment. Most important, it could even operate in water that traditional silk-based sensors cannot realize. The proposed tussah silk based sensor, integrated bio-inspired superhydrophobicity with strain response functionality, offered transformative potential for aqueous-environment applications ranging from marine exploration to medical diagnostics.