In situ 3D printing of liquid metal-hydrogel hybrid for multifunctional soft bioelectronics and devices

Hydrogels have high water content, excellent biocompatibility, and tissue-matched compliance, which are favorable for interfacing with biological tissues, and they have attracted wide attention in soft electronics. However, current difficulties, such as interconnection issues with the metallic interface, and deficient fabrication strategies still pose great challenges. Here, a facile in situ 3D printing method is developed to fabricate liquid metal (LM)-hydrogel hybrids, which enable mechanical compliance to soft tissues (∼10 kPa), thus serving as the bio-interface of hydrogel bioelectronics or devices. Moreover, LM-hydrogel hybrids have good electrical interconnection with conventional electrical interfaces due to the excellent wetting and alloyed behavior of LM and commonly used metallic conductors. The LM-hydrogel hybrid can also be directly used for electronic components or devices without any further encapsulation or assembly process. Such LM-hydrogel hybrid via this convenient and almost automatic in situ 3D printing method may set up a multifunctional platform for hydrogel bioelectronics and devices.