Fully Recyclable Liquid Metal-Based Ultra-Stretchable Electronics Enabled by Water-Modulation-Degradation-Reconstruction Polymer-Gel

The rapid development of stretchable electronics made by circuits, microchips, and encapsulation elastomers has caused the production of a large amount of electronic waste (e-waste). The degradation of elastomers can highly minimize the negative effects of e-wastes. However, chemicals that included acid, alkali, and organics were repeatedly used during the recycling process, which were environmentally unfriendly. Here, a water-modulation-degradation-reconstruction (WDR) polyvinylpyrrolidone (PVP)-honey composite (PHC) polymer-gel was developed and could be regarded as encapsulation elastomers to realize a fully recyclable water-degradable stretchable (WS) electronics with multi-functions. The stretchability of the PHC polymer-gel could be modulated by the change of its water retention. The Chip-integrated liquid metal (LM) circuits encapsulated with the modulated PHC encapsulation elastomer could withstand a strain value of ~3000%. Moreover, we developed a WS biomedical sensor composed of PHC encapsulation elastomer, LM circuits, and microchips, which could be fully recycled by biodegrading it in water to reconstruct a new one. As before, the reconstructed WS biomedical sensor could still simultaneously realize the combination of ultra-stretchability, recycling, self-healing, self-adhesive, and self-conformal abilities. The results revealed that this study exercises a profound influence on the rational design of multi-functional WS electronics.