Highly Stretchable and Conductive Copper Nanowire Based Fibers with Hierarchical Structure for Wearable Heaters.

Wearable heaters have been increasingly attracting researchers' great interest due to their efficient utility in maintaining warmth and in thermotherapy. Nowadays carbon nanomaterials and metallic nanowires tend to become the mainstream heating elements in wearable heaters considering their excellent electrical and mechanical properties. Though considerable progress has been made, there still exist challenging issues that need to be addressed in practical applications, including bad breathability and poor endurance to mechanical deformations. Here, we devise a copper nanowire based composite fiber with a unique hierarchical structure. This fiber possesses not only excellent heating performance, but also fantastic tolerance to mechanical impact, such as bending, twisting, and stretching. We further weave these fibers into a wearable heating fabric and realize smart personal heating management through an Android phone by integrating with a microcontroller unit. Two practical applications are demonstrated including a heating kneepad for articular thermotherapy and a heating coat on an infant model for maintaining warmth.