Multiscale Material Engineering of a Conductive Polymer and a Liquid Metal Platform for Stretchable and Biostable Human-Machine-Interface Bioelectronic Applications

Liquid-metal-based stretchable bioelectronics can conform to the dynamic movements of tissues and enable human-interactive biosensors to monitor various physiologic parameters. However, the fluidic nature, surface oxidation, and low biostability of the liquid metals have limited the long-term use of bioelectronics. Here we have developed a rationally designed material engineering approach to overcome these challenges in liquid metal bioelectronics. To our knowledge, this is the first demonstration of stretchable, leak-free, and highly conductive gallium-based bioelectronic devices with exceptional biostability and electrochemical properties. We first utilized unique gallium oxide properties to create 3D microscale wrinkled structures on the gallium surface. Then, gold nanoparticles and biostable poly(3,4-ethylenedioxythiophene) were successively deposited on the wrinkled liquid metal surface. We demonstrated this multilayer encapsulation material could conform to the stretching deformation and showed excellent environmental stabilities while maintaining high electrical properties. Electromyographic measurements were used to evaluate the bioelectrical performance of the stretchable electronics, and the results demonstrated the encapsulated liquid metal device could outperform bare liquid metal devices. Finally, a sensory feedback study demonstrated our liquid metal bioelectronic device could record precise physiologic signals to control robots for mimicking dexterous hand gestures. This study opens the possibility of chronic liquid-metal-based stretchable bioelectronics.