Liquid-based electronic materials for bioelectronics: current trends and challenges

Liquid-based materials have emerged as promising soft materials for bioelectronics due to their defectfree nature, conformability, robust mechanical properties, self-healing, conductivity, and stable interfaces. A liquid is infiltrated into a structuring material endowing the material with a liquid-like behavior. Liquidbased electronics with favorable features are being designed and engineered to meet requirements of practical applications. In this review, various types of liquid-based electronic materials and the recent progress on bioelectronics in multiple applications are summarized. Liquid-based electronic materials include ionic liquid hydrogel, nanomaterial-incorporated hydrogel, liquid metal, liquid-infused encapsulation, and liquid-based adhesive. These materials are demonstrated via electronic applications, including strain sensor, touch sensor, implantable stimulator, encapsulation, and adhesive as necessary components comprising electronics. Finally, the current challenges and future perspective of liquid-based electronics are discussed.