Ultra-fast programmable human-machine interface enabled by 3D printed degradable conductive hydrogel

Hydrogels are attracting enormous interests in various applications including electronic skins, tissue engineering, drug delivery, and wearable devices due to their marvelous stretchability, conductivity and ultra-high sensitivity. In the present study, we propose a new type of conductive cross-linked hydrogel fabricated by projection microstereolithography (PμSL) based three-dimensional (3D) printing technique which can be completely degraded when submerged in alkaline within tens of seconds. The tensile strengths and conductivity of hydrogels are tested to demonstrate their great performance of flexibility and conductivity. Moreover, the influences of temperature, pH value and chemical compositions on the conductivity and degradation performance of our printable hydrogels are also explored. Based on the merits of our printable hydrogel, the developed hydrogel sensors promise feasible applications of degradable, highly stretchable and conductive wearable devices and transient electronics. Most significantly, hydrogel circuits can be functionally tailored by alkaline and photocurable precursor of the printable hydrogel within tens of seconds, enabling the ultra-fast programmable human-machine interface to acquire electromyogram (EMG) signals for controlling the fingers of an extraman accurately. The present work opens a gate for designing ultra-fast programmable flexible electronics, transient electronics, human-machine interface, etc. with printed degradable conductive hydrogel.