Ultrathin and highly breathable electronic tattoo for sensing multiple signals imperceptibly on the skin

The ideal epidermal electronics is desired to be comfortable to wear (e.g., imperceptible and breathable), simple to prepare without losing functionality. But real epidermal electronics always trade off its functionality, comfortability, and fabrication complexity. Herein, we present an ultrathin, breathable (20.5 mg/cm2h), multifunctional electronic tattoo (e-tattoo) that can be manufactured efficiently and cheaply. Ultrathin (0.15–11.09 µm) and porous thermoplastic polyurethane (TPU) film, obtained by combining simple rod-coating and polymer solution phase separation, provide excellent breathability for the devices. Silver nanowires (AgNWs) are sprayed on the porous film surface to form a strain-insensitive conductive layer. Based on porous films, a series of functional modules such as electrophysiological sensing, epidermal moisture sensing, touch sensing (with self-signal recognition), and pressure sensing (no interference with skin sensation) are described in the work. Experiments have shown that ultrathin and breathable e-tattoos have good conformability and can work imperceptibly on the skin for a long time. This e-tattoo with excellent comprehensive performance provides new ideas in health monitoring, human-computer interaction, and tactile information detection, and contributes to the development of next-generation epidermal electronic platforms.