Laser-Activated Metallization-Based Hybrid Additive Manufacturing Technology for 3D Flexible Electronics

Flexible electronics is an exciting and cutting-edge field that involves the development of electronic devices that can bend, stretch, and flex while maintaining their functionality. With the rapid advancement of wearable electronics, soft robotics, and medical devices, there is an urgent demand for a facile and scalable manufacturing technology that is able to deliver geometric-complex flexible electronics with customized functionalities. Herein, we successfully developed a hybrid additive manufacturing (HAM) technology that combines vat photopolymerization (VPP) 3D printing, laser-activated selective electroless plating (LASELP) process, and liquid metal coating to customize 3D flexible electronics, which significantly enhanced the design freedom and manufacturing capability of 3D flexible electronics. The copper conductor deposited on a 3D-printed flexible substrate possessed a conductivity of 2.04 × 10⁷ S m^-1, which is much higher than the commonly used electrically conductive adhesives. With the coating of liquid metal, the resistance change of the metallic conductor was suppressed during large deformation and the resistance only increased by 20% when the substrate was stretched to break at a strain of 44%. 3D stretchable interconnecting wires, a self-sensing pneumatic robotic gripper, and a flexible finger rehabilitation device were developed to demonstrate the feasibility and potential of this HAM technology for the applications of wearable devices, smart robots, and medical devices.