Influences of two sizes of nano-Fe3O4 on stereolithography 3D printing properties of gel photoresist for photothermal-responsive hydrogel

Nanocomposite hydrogels enable augmented properties, functions, and responsive behaviors. In the field of stereolithography 3D printing of the photothermal responsive nanocomposite hydrogel, the influence of the size of nano-Fe3O4 on 3D printing properties is significant due to the sedimentation, but the relevant research is rare. In this study, for the fabrication of photothermal responsive hybrid hydrogel, poly(N-isopropylacrylamide-acrylamide)/nano-Fe3O4 [P(NIPAM-AM)/nano-Fe3O4] gel photoresist was prepared and digital light processing (DLP)-based 3D printing as one of the popular stereolithography 3D printing technology was utilized. The influences of two sizes of Fe3O4 nanoparticles (10 and 50 nm) denoted as nano-Fe3O4(10) and nano-Fe3O4(50) on DLP 3D printing properties of the gel photoresist were investigated in detail. The results reveal that the gel photoresist with nano-Fe3O4(10) obtained long exposure time for the basic prototype, low overcuring degree (Od), and good uniformity of nanoparticles in hybrid hydrogels, while those with nano-Fe3O4(50) had the merits of printing high 3D sample due to the low release fore. Unfortunately, the gel photoresist with a high content of nano-Fe3O4 such as 3.11 wt% failed in 3D printing of a high and uniform gel cylinder. A strategy of preparing P(NIPAM-AM)/nano-Fe3O4 gel photoresist with mixed nano-Fe3O4(10) and (50) for 3D printing was proposed. Using the gel photoresist (nano-Fe3O4 content: 3.11 wt%) with two sizes of nano-Fe3O4 mixed with 50% each and the exposure time of 8 s, a gel cylinder with a height of 1 cm was successfully printed with uniform nano-Fe3O4 distribution and low Od values (≤ 1.17%). Further, a biomimetic hydrogel octopus was 3D printed by using the gel photoresist with mixed nano-Fe3O4 and thereafter a near-infrared-light-driven waving motion of octopus tentacle was achieved successfully. [Display omitted] •Photothermal-responsive nanocomposite hydrogel is stereolithography 3D printed.•Gel photoresists containing small or large nano-Fe3O4 have various printing features.•Mixed usage of 10 and 50 nm of Fe3O4 profits the printing feasibility and uniformity.•3D printed hydrogel octopus reveals good light-driven biomimetic waving motion.