Abstract
Light-responsive hydrogel actuators show attractive biomedical applications for in vivo drug delivery tool, surgical tissue repair operation, and vascular cleaning due to its non-contact, rapid, precise, and remote spatial control of light. Conventional visible–light–responsive hydrogels contain special chemical structure or groups, and the difficulty in synthesis results in that few can be applied to fabricate visible–light–driven hydrogel actuators. In this study, based on photothermal effect, surface-modified Fe3O4 nanoparticles were incorporated into poly(N-isopropylacrylamide-acrylamide) hydrogel by UV photopolymerization, which revealed excellent green–light–responsive volume change. Under a laser irradiation of 200 mW at 520 nm, the bending angle deformation of hydrogel strips with 2.62 wt% Fe3O4 reached 107.8°. Strip-shaped hydrogel actuators could be applied to transport tiny objects. Furthermore, a boomerang-like hydrogel actuator was designed and fabricated to drive floating foam on water. By 12 cycles of continuous laser on–off irradiation to a hydrogel actuator underwater, a circular returning movement of the float was accomplished. The study on driving a float using visible–light–triggered hydrogel actuators provides a new idea for the design of light-driven biomedical devices and soft robots.
Highlights
Hydrogels are three-dimensional water-swollen polymeric networks, similar to soft tissues, which exhibit dramatic volume changes in response to various environmental stimuli (Li G. et al, 2020; Jiao et al, 2020; Gao et al, 2020)
The morphology of the P(NIPAM-AM)/Fe3O4 nanocomposite hydrogel was observed by SEM (Figure 2B), which shows that the hybrid hydrogel acquires loose and porous structures with pore dimensions ranging from hundreds of nanometers to several micrometers
Aggregation of Fe3O4 NPs was observed in dried hydrogel networks (Figure 2C)
Summary
Hydrogels are three-dimensional water-swollen polymeric networks, similar to soft tissues, which exhibit dramatic volume changes in response to various environmental stimuli (Li G. et al, 2020; Jiao et al, 2020; Gao et al, 2020). Shi et al reported near-infrared (NIR) light-responsive poly(N-isopropylacrylamide)/graphene oxide (PNIPAM/GO). Chen et al reported a photo-responsive hydrogel with enhanced photo-efficiency and decoupled process of light activation by incorporating the triphenylmethane leucohydroxide and 2-nitrobenzaldehyde molecules into a polyacrylamide hydrogel (Chen et al, 2020) They demonstrated reprogrammable light patterning of the hydrogel with precisely controlled geometry under UV irradiation at 365 nm. Reported a series of azobenzene boronic acids that reversibly controlled the extent of diol binding via photochemical isomerization (Accardo et al, 2020) By tethering this photoswitch to a poly(ethylene glycol) star polymer, they could tune the stiffness of covalent adaptable hydrogels using different wavelengths (450–626 nm) of visible light.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
