Stretchable, Transparent and Multifunctional PVC-gel Heater: A Novel Approach to Skin-Mountable, Wearable Thermal Devices.

Abstract The electric heaters based on functional material and design have been developed to realize the various multifunctional applications. In this work, the functional heater consisting of polyvinyl chloride (PVC)-gel heater and hydrogel electrode, for the first time, is proposed, which exhibits high stretchability, transparency and capacity to generate diverse thermal patterns through spatially localized heating. The proposed heater is capable of generating the uniform temperature distribution at the heated area under extreme strains up to 400%. Besides, its transparency over 86% transmittance across the visible range renders it highly suitable for wearable or skin-mountable applications in an aesthetic viewpoint. Thanks to its localized heating ability, the proposed heater is capable of being extended to pixelated heater array which is row/column addressable and transfers diverse thermal pattern, while it is still stretchable and transparent, demonstrating 5 x 5 heater array. Various applications are demonstrated such as the skin-mountable thermo-haptic devices, wearable thermotherapy, and controlled thermal pattern generations, all of which show its superior mechanical, optical and thermal advantages. This innovative functional heater can expand the possibilities for transferring the thermal information and sensation integrated with visual cues in the next-generation skin-mountable and wearable electric heating devices.