Highly Conductive Cellulose Strain Sensor with Excellent Negative Resistance Variation and Joule Heating Property

The rational design of a wearable strain sensor with heating property has attracted great interest. In this study, a flexible conductivity hierarchical cellulose strain sensor (MX@Ag@CY) with heating property was fabricated via in situ formation of silver nanoparticles (Ags) on cotton yarn (CY) and subsequent dip-coating with MXene (MX). Ags coupled with MX coating endowed the cotton yarn with a high conductivity, where the resistance of the optimized composite MX@Ag0.47@CY was about 22 Ω/cm. Compared with the previously reported strain sensors, the woven MX@Ag0.47@CY fabric strain sensor showed a distinctive negative resistance variation, wherein it showed an enhanced conductivity with the increased strain owing to its unique architecture. The woven MX@Ag0.47@CY fabric strain sensor exhibited a repeatable response and displayed long-term stability in the strain range of 0–55%. In addition, the strain sensor demonstrated great detectability on large-scale human movements when directly attached to the elbow, wrist, or knee. Furthermore, when MX@Ag0.47@CY served as a heater (at an applied DC voltage of 6 V), it presented high heating temperature (92.4 °C), homogeneous temperature distribution, low operation voltage (1–6 V), and excellent thermal stability even under strain.