Digital Light Processing of Three-dimensional Liquid Metal Hydrogels

Liquid metal (LM) hydrogels emerge as promising materials for flexible electronics and soft robotics, but they are challenged by simplistic structure, limited precision, and insufficient functional designability. Herein, we demonstrate the first digital light processing of three-dimensional (3D) LM hydrogels with micrometer precision (10 µm) and arbitrarily elaborated architectures. A universal strategy is developed for photo-curable LM-based various resins by encapsulation of LM droplets with sodium alginate (SA). The SA coating not only prevents the ink from sedimentation and self-polymerization by forming hydrogen and ionic bonds, but also ensures uniformly dispersed ink with maintained photo-curing properties. As a result, the photo-cured 3D LM hydrogels illustrate enhanced tensile stretchability (2000%) and cycling stability (800 cycles at 500% strain), which outperforms most previously reported 3D hydrogels. The 3D LM hydrogel also shows enhanced sensitivity and tunable photothermal responsivity, demonstrating promising applications in strain sensors, object grasping robotics, remote-controlled devices, and anti-counterfeiting systems.