Light-Driven Flagellated Micro-Gel Robot Made of Temperature-Responsive Hydrogel Actuator

In recent years, biomimetic microrobots are attracting large attention. Conventional microrobots that are inspired by living microorganisms mainly employ helical structure and be driven by a magnetic field. Thus, the motion of them is not similar to real microorganisms. To realize a microrobot that can reproduce the motion of real microorganisms, we propose a biomimetic micro-gel robot that can swim by flagella-like motion. In this paper, we succeeded in realizing swimming of micro-gel robot with flagella-like structure. An actuator of the microrobot is made of a temperature-responsive hydrogel and it is actuated by heating it with laser irradiation. We fabricate the robot with sacrificial layer process using dextran, and succeeded in acquiring freely movable micro-gel robot. Furthermore, laser scanning on the robot realizes sequential bending motion of the flagella-like actuator and swimming of the micro-gel robot. We also evaluated a relationship between scanning speed of the laser and swimming speed with different laser power to evaluate an optimal drive condition. Then, we fabricated robots with various lengths of the actuator, and we evaluated non-dimensional velocity by normalizing the velocity with the length of actuator. From the results, it is suggested that flagellar propulsion is suitable for micro-scale.