Fabrication\nof Highly Stretchable, Washable, Wearable,\nWater-Repellent Strain Sensors with Multi-Stimuli Sensing Ability

Abstract

Stretchable\nand wearable sensors with active response to various\nenvironmental stimuli possess numerous potential applications in stretchable\nelectronics, motion sensors, environmental monitoring, and so on.\nHerein, we report a new method to realize control on the local conductive\nnetworks of strain sensors, thus, their sensing behavior. These multifunctional\ncrack-based sensors were prepared via spray coating a mixture of carbon\nnanotube (CNT) and 3-aminopropyltriethoxysilane (KH550) with various\nratios onto polydimethylsiloxane (PDMS). The conductive CNT/KH550\nlayer exhibits brittle mechanical behavior which triggers the formation\nof cracks upon stretching. This is thought to be responsible for the\nobserved electromechanical behavior. These sensors exhibit adjustable\ngauge factors of 5–1000, stretchability (ε) of 2–250%,\nlinearity (nonlinearity–linearity) and high durability over\n1000 stretching–releasing cycles for mechanical deformation.\nWashable, wearable, and water-repellent sensors were prepared through\nsuch a method to successfully detect human physiological activities.\nMoreover, the variation in temperature or the presence of solvent\ncan also be detected due to the thermal expansion and swelling of\nthe PDMS layer. It is expected that such a concept could be used to\nprepare sensors for multiple applications, thanks to its multifunctionality,\nadjustable and robust performance, simple and low-cost fabrication\nstrategy.