Bioinspired Photonic Ionogels as Interactively Visual Ionic Skin with Optical and Electrical Synergy

With the ever-growing demands for flexible smart interactive electronics, it remains highly desirable yet challenging to design and fabricate interactive ionic skin with multiple signal synergistic outputs. Herein, high-performance photonic ionogels (PIGs) with excellent stability and synergy sensitivity are designed by locking a non-volatile and non-hygroscopic ionic liquid (IL), that is, 1-ethyl-3-methylimidazolium bis-(trifluoromethylsulfonyl)imide ([EMIm][TFSI]), into photonic elastomers based on polymer networks of poly(ethylene glycol) phenyl ether acrylate (PEGPEA). Through manipulating the degree of crosslinking, PIGs exhibit high sensitivity that can output distinct and intuitive color change in visual with the mechanochromic sensitivity of ≈1.76 nm per percent strain and clear electrical signal with the gauge factor of 1, in response to a tiny stretch of millimeter scale. Thanks to the stable photonic elastomers and IL employed, the PIGs developed in this study exhibit good performance under harsh and complex environmental conditions, including high/low temperature (from -35 °C to 100 °C), dry/wet air, and high vacuum. This study provides a novel strategy for developing integrated, stable, and multifunctional photonic ionogels for ionic skin sensors and flexible interactive devices with synergistically optical and electrical output.