A highly sensitive and stretchable strain sensor based on a wrinkled chitosan-multiwall carbon nanotube nanocomposite

Recently, flexible wearable sensors have been widely used in the fields of health supervision, motion monitoring, human-computer interactions and electronic skin. However, it is a huge challenge to fabricate strain sensors with a low detection limit, high sensitivity, and large strain range. In this work, we developed a high-performance strain sensor with a wrinkled chitosan (CS)-multiwall carbon nanotube (MWCNT) sensing layer. It could be fabricated via spraying CS/MWCNT solution on pre-stretched polydimethylsiloxane (PDMS), and releasing it to obtain a wrinkled structure. Because of the good film-forming properties of CS and free stretchability of the wrinkled structure, the strain sensor has a low detection limit (<= 0.4%) and a wide detection range (similar to 80%) that meets the need for monitoring human movement. It also holds excellent stability (>1500 cycles) and high sensitivity, in which the gauge factor has values of up to 23.4 (0% <= Delta epsilon < 45%), 1020 (45% <= Delta epsilon < 70%) and 3317 (70% <= Delta epsilon < 80%). Therefore, it can not only sense weak signals like pulse and respiration, but can also detect large strain signals like vocalization and joint bending. Importantly, the sensor signals can be monitored in real time via mobile devices. Moreover, an array composed of this sensor exhibits excellent performance for detecting pressure distribution and external stimuli.