Stretchable helical fibers with skin-core structure for pressure and proximity sensing

As a multifunctional monitoring platform based on the human environment, fiber-based capacitive sensors are promising wearable electronic devices. However, it is of great challenge to select suitable dielectric materials and construct a bimodal capacitive sensor with excellent stretchability, high compatibility and stable sensing capability. Here, we report a bacterial cellulose (BC)@BC/carbon nanotube (CNT) helical fiber with skin-core structure, and biodegradable BC as the skin and conductive BC/CNT as the core, which exhibits tensile strength of 148 MPa and break elongation of 536 %. Two helical fibers are cross-assembled into a bimodal sensor, dedicated to detecting pressure and proximity. In the contact mode, the capacitance of the sensor increases with the increase of the pressure (0–50 N) with good sensitivity of 2.92 N−1. In the noncontact mode, the sensor exhibits a monitoring range of 0–20 cm, and the capacitance change rate is 31 % when the finger is close to 0.5 cm. Additionally, our bimodal sensor can be used to detect the body’s omnidirectional motion and even help referees to efficient judgment in sports. In a word, our capacitive sensor provides a tremendous advantage and foundation for the development of smart fibers and the research of intelligent textiles.