Dual-Modal 3D Locomotion of Magnetically Actuated Millirobots in Elongated Narrow Conduits

Magnetically actuated miniature robots have great potential for biomedical applications such as targeted drug delivery and intestinal interventions. However, it is challenging to realize gravity-resistant 3D locomotion in elongated narrow conduits, where scales reach the millimeter level and inertial forces, especially gravity, cannot be ignored. Addressing this challenge, we developed a millirobot with an optimized helical structure guided by topology optimization. Based on a structural optimization and density regulation approach, we achieve helix-like millirobots capable of resisting gravity and performing dual-modal 3D locomotion in narrow conduits. Experimental validation shows that the designed millirobot can stably move in a horizontal conduit with a maximum speed of 4.91 mm/s and resist gravity to rise vertically in a vertical conduit with a maximum rise speed of 8.96 mm/s under the action of a programmable rotating magnetic field. The robot provides a novel solution for the use of magnetically controlled robots for biomedical applications in complex tubular conduits.