Stretchable, Stable, and Degradable Silk Fibroin Enabled by Mesoscopic Doping for Finger Motion Triggered Color/Transmittance Adjustment.

As a kind of biocompatible material with long history, silk fibroin is one of the ideal platforms for on-skin and implantable electronic devices, especially for self-powered systems. In this work, to solve the intrinsic brittleness as well as poor chemical stability of pure silk fibroin film, mesoscopic doping of regenerated silk fibroin is introduced to promote the secondary structure transformation, resulting in huge improvement in mechanical flexibility (∼250% stretchable and 1000 bending cycles) and chemical stability (endure 100 °C and 3-11 pH). Based on such doped silk film (SF), a flexible, stretchable and fully bioabsorbable triboelectric nanogenerator (TENG) is developed to harvest biomechanical energy in vitro or in vivo for intelligent wireless communication, for example, such TENG can be attached on the fingers to intelligently control the electrochromic function of rearview mirrors, in which the transmittance can be easily adjusted by changing contact force or area. This robust TENG shows great potential application in intelligent vehicle, smart home and health care systems.

All-Textile Electronic Skin Enabled by Highly Elastic Spacer Fabric and Conductive Fibers.

Electronic fabrics that combine traditional fabric with intelligent functionalities have attracted increasing attention. Here an all-fabric pressure sensor with a wireless battery-free monitoring system was successfully fabricated, where a 3D penetrated fabric sandwiched between two highly conductive fabric electrodes acts as a dielectric layer. Thanks to the good elastic recovery of the spacer fabric, the capacitance pressure sensor exhibits a high sensitivity of 0.283 KPa-1 with a fast response time and good cycling stability (≥20 000). Water-soluble poly(vinyl alcohol) template-assisted silver nanofibers were constructed on the high-roughness fabric surface to achieve high conductivity (0.33 Ω/sq), remarkable mechanical robustness, and good biocompatibility with human skin. In addition, the coplanar fabric sensor arrays were successfully designed and fabricated to spatially map resolved pressure information. More importantly, the gas-permeable fabrics can be stuck on the skin for wireless real-time pressure detection through a fiber inductor coil with a resonant frequency shift sensitivity of 6.8 MHz/kPa. Our all-fabric sensor is more suitable for textile technology compared with traditional pressure sensors and exhibited wide potential applications in the field of intelligent fabric for electronic skin.