A mechanically enhanced electroactive hydrogel for 3D printing using a multileg long chain crosslinker

Electroactive hydrogels (EAHs) are receiving attention in soft robotics. 3D printing makes EAHs even more attractive, due to the diversification and elaboration of actuations. However, 3D printing needs a large amount of photoinitiator for faster printing, which makes the printed hydrogels so brittle that they cannot produce large scale 3D printing. Here, we developed a 3D printable EAH based on poly(3-sulfopropyl acrylate, potassium salt) (PSPA) using glycidyl methacrylated hyaluronic acid (GMHA) as a mechanically enhancing multileg long chain (MLLC) crosslinker. The MLLC crosslinking improved the stretchability of the PSPA-based hydrogel to 49% from 28%, while maintaining the same level of electroactivity. Additionally, the fracture toughness of the PSPA-based hydrogel remarkably increased from 11 to 40 J m^-2 with crosslinking by the MLLC. Using the mechanically enhanced EAH, i.e. the GMHA-PSPA EAH, the 3D printing of elaborate structures, e.g. 'Leaning Tower of Pisa' and a hand, and their electroactuation were successfully demonstrated.