Bioinspired Strain Sensor Using Multiwalled Carbon Nanotube/Polyvinyl Butyral/Nylon Cloth for Wireless Sensing Applications

The mushroom growth of wearable electronics greatly stimulates the demand of flexible strain sensors, and it makes sense to design a manufacturing method that avoids unknown biotoxicity, high-temperature treatment, and redundant technical route. Here, inspired by the geometry of slit receptor on spiders, we prepare a crack-based strain sensor using a facile, cost-effective and large-area-capable method. Conductive inks made of multiwalled carbon nanotubes (MWCNTs) and polyvinyl butyral (PVB) are drop onto nylon cloth, and then pre-stretched to 50% strain to generate long-range ordered and self-organized microcracks. Experimentally, the crack-based strain sensor delivers a superfast response time ( $\sim 31$ ms), balanced sensitivity and strain range (a gauge factor of 81.45 in the $15-50$ % strain range), and good reliability (>2500 cycles). These excellent sensing properties are attributed to the V-shaped microcrack structure that initiates significant resistance changes during repeated stretching/release. Meanwhile, the nylon substrate provides stable mechanical resilience to meet multiple stretching cycles. Combined with the wireless transmission system, the resistance signal measured by the strain sensor can be transmitted through Bluetooth and displayed in the mobile phone, realizing the real-time monitoring of human health and movements.