Covalent Crosslinker-Free Photo-Curing 3D Printing of Liquid Metal Composite Hydrogels Based On SI-photoATRP.

Photocurable 3D printing (SLA or DLP) materials have garnered considerable attention due to their remarkable efficiency and precision in manufacturing. However, the presence of covalent crosslinking makes the recycling and reuse of printed materials extremely challenging. Here a novel approach to covalent crosslinker-free photo-curing 3D printing (via DLP) of liquid metal (LM) composite hydrogels is reported, leveraging surface-initiated photoinduced atom radical transfer polymerization (SI-photoATRP). The pre-synthesized PHEA-Br macroinitiators are grafted onto the surfaces of LM nanoparticles (LMNPs) by mechanical sonication, stabilizing the LMNPs within the resin solution while simultaneously generating active sites for SI-photoATRP. During the SI-photoATRP process, polymer chains of sufficient length form hydrogen bonds with multiple LMNPs, effectively transforming the LMNPs into crosslinking points. By integrating the aqueous photoATRP system catalyzed by carbon dots, LM@polymer composite hydrogel with complex structures are successfully established through DLP technology. The versatility of the 3D printed hydrogel is investigated by employing HEA, OEGA and AAm as the monomers in resin solution, respectively. Notably, all the LM@polymer composite hydrogels can be degraded in aqueous NaOH solution. Furthermore, LM@polymer-based networks exhibit self-repairing capabilities, serve as underwater adhesives, and conduct electricity. This work offers new insights into designing 3D printing materials and sustainable photocurable technology.