Superhydrophobic, Transparent, and Stretchable 3D Hierarchical Wrinkled Film-Based Sensors for Wearable Applications

There is currently a high demand for smart wearable and flexible electronics for high-sensitivity strain sensors with good transparency, stretchability, and water-repellent characteristics. The demand for such devices, especially those that demonstrate superhydrophobicity, is constantly increasing because of their prospective wearable applications. A stretchable, superhydrophobic, and transparent polydimethylsiloxane/carbon nanotube strain sensor is fabricated by directly spraying a carbon nanotube solution onto a polydimethylsiloxane nanowrinkle substrate. Applying this coating not only provides many substrate materials with a superhydrophobic surface, but also responds to stretching, bending, and torsion—properties that benefit flexible sensor applications. The strain sensor shows high optical transparency (over 70%) and displays excellent superhydrophobicity (a water contact angle of 165 ± 2°). It shows a good response, with over 5000 stretching–relaxing cycles and 10 000 cycles with twisting angles from 0° to 20°, and is able to sense strain for stretching of up to 80%, bending of up to 140°, and rotation of up to 90°. These findings demonstrate the validity of this approach for fabricating transparent superhydrophobic materials with excellent stretchability and conductivity characteristics. Such materials show great potential for wearable devices to detect human motion, including large-scale movements, without affecting the appearance of the device.