Laser-induced sol–gel transition for high-resolution magnetic patterning of hydrogel actuators

Abstract This paper presents a novel magnetization patterning method for magnetic hydrogel actuators using laser-induced sol–gel transition. While conventional magnetically driven soft actuators typically use silicone matrices and neodymium magnetic particles, we demonstrate a new approach using agar hydrogel and ferrite particles. The agar matrix undergoes sol–gel transition upon laser heating, allowing localized reorientation of magnetic particles, while ferrite particles maintain their magnetic properties due to their high Curie temperature. We investigate the relationships between laser parameters and pattern dimensions, achieving pattern widths down to 100 μm. Through overlapping scan patterns, we further improve resolution to 50 μm pitch. The effects of sample thickness and applied magnetic field strength on actuation behavior are systematically evaluated using a beam deformation model. This method enables precise control of magnetization patterns in hydrogel-based soft actuators, offering potential applications in biomedical fields.