Weft‐Knitted Fabric for a Highly Stretchable and Low‐Voltage Wearable Heater

Wearable heaters have attracted broad attention due to their applications in personal heating systems and healthcare management, such as heat preservation in textile/clothing and thermotherapy. Protecting heating performance against deterioration under large deformation is is important for the application of wearable heaters. Here, a highly stretchable electrically driven heater based on electrically conductive weft‐knitted fabrics is reported, which can be transformed from traditional fabrics through a facile heat treatment process. As an example, a heater made from Modal shows a heating temperature higher than 100 °C at a driving voltage as low as 3 V. The Joule heating performance of the heater does not deteriorate even under a large strain of 70%. Furthermore, according to theoretical analysis and experimental results, the output power and saturated temperature of the heater under a certain voltage can be easily tuned by tailoring the shape and size of the fabric to meet customized demands. The superior performance of the heater originates from the weft‐knitted structural configuration. Finally, the application of the ultrastretchable heater in wearable thermal therapy devices is demonstrated, showing its great potential in wearable electronics.