Adv. Funct. Mater. https://doi.org/10.1002/adfm.201808695 (2019)

Lightweight and soft epidermal electronics mimicking the morphology of human skin are promising candidates for applications in wearable sensing, particularly in health monitoring. Recently, self-healing electronic tattoos have been developed to tackle the mechanical damage that occurs during long-term wear. Now, Q. Wang and co-workers report a self-healable and biocompatible silk electronic tattoo designed for multiple stimuli sensing.

The device concept relies on a combination of graphene incorporated with soft and flexible silk fibroin (SF) Ca2+ membrane that can be directly transferred to human skin. The graphene/SF/Ca2+ composite can heal itself with 100% efficiency after damage by water, because of dynamic hydrogen and coordination bonds present in the membrane. The electronic tattoo shows multiple sensing functionalities. In particular, when used as a strain sensor, the device exhibits high gauge factors and excellent tensile strain durability. Its humidity sensing performance is reproducible and stable with fast response and recovery rate. Remarkably, the temperature sensitivity of the wearable device is comparable to or better than that of previously reported carbon-based temperature sensors.