Multifunctional visualized electronic skin based on a solvatochromic poly (ionic liquid) ionogel

The biological skins exhibit various fascinating visual functions, such as turning red in response to strain, whitening upon hydrogen peroxide stimulation, and changing color in accordance with the environment (octopus). Inspired by these phenomena, two kinds of multifunctional visualized electronic skin (e-skin) were designed and fabricated based on a novel poly (ionic liquid) ionogel. Herein, we reported a transparent and conductive poly (ionic liquid) ionogel (P(AAm-IL)) by photopolymerizing acrylamide (AAm) with 1-vinyl-3-butylimidazolium tetrafluoroborate (ionic liquid, IL) in ethylene glycol (EG). Interestingly, P(AAm-IL) displays a solvatochromic phenomenon, and typical hydrogen-bonding acceptor solvents like acetone, methanol, and nitromethane induce a whitening effect in it. Based on this ionogel, we fabricated multifunctional strain sensors integrated with the visualized chemical sensing ability. The discoloration mechanism of the chemical sensing was detailed studied. Furthermore, by combining the P(AAm-IL) ionogel with Lithium trifluoroethane sulfonate (LiTf), the blend P(AAm-IL)-Li ionogel exhibits enhanced stretchability (>4300 %), higher conductivity (1.44 × 10−2 S·m−1), good transparency (>80 %) as well as wide operating temperature range (−20 to 80 °C). A sandwich-structured e-skin (Polypyrrole/PAAm-IL-Li/CsPbBr3-TPU) exhibiting both electro-optical dual response to strain was successfully fabricated. The luminescent e-skin not only exhibits highly sensitive electrical responses but also demonstrates visible fluorescence changes in response to external strain variations. These multifunctional visualized e-skins demonstrate great potential for applications in chemical environmental monitoring robotics, wearable electronic devices, and human–computer interaction.