Formation of hydrogel microspring by using bevel-tip capillary for soft actuator

This paper describes a hydrogel microspring formed by using a bevel-tip capillary and its application for a soft actuator. The hydrogel microspring was formed by extruding sodium alginate pre-gel solution into calcium chloride solution using a bevel-tip microfluidic capillary. We conducted experiments of changing relevant parameters such as flow velocity, tip angle of bevel-tip capillary and diameter of capillary. Based on those results, we suggest a model of the microspring formation. As an application of soft actuators, we encapsulated magnetic nanoparticles inside a hydrogel microspring and successfully actuated the microspring by applying magnetic field. We believe that our hydrogel microsprings could be used for various applications including actuators, sensors and scaffolds for cells.