Continuous fabrication of near-infrared light responsive bilayer hydrogel fibers based on microfluidic spinning

Hydrogel microfibers with inhomogenous structure can achieve some complex motions such as bending, folding and twisting. So it can be applied to soft actuators, soft robots and micropumps. In this paper, continuous bilayer hydrogel fibers in which one layer is calcium alginate hydrogel and the other is linear poly(N-isopropylacrylamide) (PNIPAM)/calcium alginate/graphene oxide (GO) semi-interpenetrating hydrogel were prepared based on microfluidic spinning method. The results show that the bilayer hydrogel fibers have particular porous internal structures of semi-IPN hydrogels and the pore size becomes smaller with the increase of GO content. Besides, the bilayer hydrogel fibers can bend response to the temperature and near-infrared (NIR) light. The diameter of the hydrogel fibers can be tuned by changing the flow rate of spinning fluid and the take-up velocity of winding device.