2, Donghua University, Shanghai, , China
Lightweight, flexible, and wearing comfortable personal thermal management (PTM) device with desirable performance becomes prevalent because of its potential to wisely adjust our body temperature to a thermally-safe and comfort state. In this work, we report a freestanding, flexible/foldable, and large-area ultrathin graphene papers (GPs) with high thermal conductivity and sensitive electro-thermal response, and their application to wearable bifunctional PTM devices for heating and cooling. The heating part is achieved by taking advantages of its joule heating, while the cooling part benefits from its high thermal conductivity which from the ultrathin and compact lateral structure of the GPs. The promising electrical conductivity grantees the superior Joule heating for extra warmth of 42 °C using a low supply voltage around 3.2 V. Besides, based on its high thermal conductivity, the graphene paper provides passive cooling via thermal transmission from the human body to the environment within 7s. The cooling effect of graphene paper is superior compared with that of the normal cotton fabric, and this advantage will become more prominent with the increased thickness. The present bifunctional graphene paper possesses high durability against bending cycles over 500 times and wash time over 1500 min, suggesting its great potential in wearable PTM. Furthermore, we integrated the GPs into textiles by the techniques of plain weave, co-woven, hollow-out, and kirigami. These wearable technology designs achieve not only the personal thermal management, but also the breathability of the PTM devices. It can bring inspiration to the development of intelligent clothing in the future.