Microrobots have attracted considerable attention due to their immense potential for biomedical and engineering applications in recent years. Inspired by human walks, a bipedal microwalker capable of standing and walking like humans regulated by external weak magnetic fields was reported in this paper. The walker has a submillimeter size and a simple arrowhead shape. Its standing and walking locomotion is controlled by external oscillating magnetic fields generated by orthogonal electromagnetic coil pairs. The walking speeds of the microwalker are controlled using magnetic fields with varying parameters. The walking speeds on a glass substrate immersed in water could reach up to 2.2 mm s⁻¹. Designed walking paths of the microwalker on a horizontal substrate are also demonstrated. Besides walking on horizontal flat surfaces, the microwalker can climb up slopes and walk freely in circular microtubes. The microwalker is of interest in fundamental robotic gait research and for micromanipulation applications.

The capillary action between two solid surfaces has drawn significant attention in micro-objects manipulation. The axisymmetric capillary bridges and capillary forces between a spherical concave gripper and a spherical particle are investigated in the present study. A numerical procedure based on a shooting method, which consists of double iterative loops, was employed to obtain the capillary bridge profile and bring the capillary force subject to a constant volume condition. Capillary bridge rupture was characterized using the parameters of the neck radius, pressure difference, half-filling angle, and capillary force. The effects of various parameters, such as the contact angle of the spherical concave gripper, the radius ratio, and the liquid bridge volume on the dimensionless capillary force, are discussed. The results show that the radius ratio has a significant influence on the dimensionless capillary force for the dimensionless liquid bridge volumes of 0.01, 0.05, and 0.1 when the radius ratio value is smaller than 10. The effectiveness of the theorical approach was verified using simulation model and experiments.

The micro soft robot which mimics the movement of microorganisms is one of the important research directions in the field of robotics. This study proposes a programmable 3D printing method for magnetically driven micro soft robots based on surface tension. High-performance surfactant was used to reduce the surface free energy of the printing substrate, so that the liquid printing material can maintain a stable shape under the effect of surface tension. Pre-printed auxiliary lines with ultraviolet curing adhesive made the subsequently printed silicone maintain its shape defined by the auxiliary lines in the plane, and the thickness of its shape was adjusted by controlling the total amount of silicone. Silicone mixed with and without neodymium–iron–boron powder was printed into different areas successively, which eventually combined into a magnetically driven micro soft robot with a specific two-dimensional structure. Magnetically driven motion experiments confirmed that micro soft robots with different driving modes can be manufactured by this 3D printing method, and the influences of printing parameters as well as magnetically driven parameters on the motion performance of the microrobots are studied.