Printing paper-derived ultralight and highly sensitive E-skin for health monitoring and information encryption

Simplified fabrication technology and excellent sensing performance are highly desired for the development of flexible and user-friendly wearable sensors. However, there is usually a trade-off between the simplicity of the fabrication technology and the sensing performance of the device. Recently, paper-based wearable sensors have attracted much attention due to their excellent flexibility, simplified preparation, and low cost etc. However, the pressure sensitivity of the paper-derived sensors is far from satisfactory. In this work, a strategy of pencil graphite frottage (PGF) is reported by employing sandpaper as template and a pencil sketch technique to achieve functional printing paper as pressure-sensitive layers for electronic skin (e-skin). As a result, the e-skin prepared by our PGF technique shows excellent reproducibility and pressure sensing performance, including a maximum sensitivity of 7202.2 kPa(- 1), a fast response time of 25.0 ms, and an excellent durability over 20,000 loading/ unloading cycles, and high ambient stability (> 6 months). For application demonstration, the e-skins are applied to monitor human wrist pulses, acoustical vibration and information encryption. Furthermore, pressure sensing arrays are developed and employed to map the spatial pressure distribution, indicating potential application in intelligent robots and prosthetics. It is believed that the fabrication strategies proposed in this work can bring insight onto the other area of bionic e-skin and multifunctional sensor devices.