Compositional Design of an PEO-PPO-PEO copolymer-Based Support Matrix for Embedded 3D Printing of Liquid Metal

Embedded 3D printing enables the fabrication of freeform three-dimensional structures by depositing functional inks within a viscoelastic support matrix. The composition and physical properties of the matrix are critical for maintaining printed geometry and ensuring uniform ink deposition. In this study, a PEO-PPO-PEO copolymer-based support matrix was developed for the stable embedded 3D printing of high-density liquid metal. The effects of copolymer concentration and photocrosslinkable components on printing performance were investigated. Low-concentration PEO-PPO-PEO matrices exhibited insufficient recovery of the paths created by needle movement. Moreover, their reversible thermogelling behavior caused the matrices to regain fluidity at lower temperatures, limiting the stable fixation of printed structures. To address these limitations, acrylamide and a photoinitiator were incorporated into the matrix, followed by photocrosslinking under 395 nm ultraviolet light. The photocrosslinked composite matrix exhibited suitable viscosity and enabled the formation of relatively uniform, well-defined liquid-metal lines. When the PEO-PPO-PEO concentration was doubled, the matrix maintained printability under heated conditions even in the presence of acrylate components. The increased copolymer concentration also reduced trapped air bubbles, resulting in more uniform printing. These results demonstrate that controlling the PEO-PPO-PEO concentration and photocrosslinked polymer network is essential for improving the stability and quality of embedded liquid-metal printing. This study provides a support-matrix design strategy for fabricating liquid-metal-based soft electronic devices and functional three-dimensional structures.