Selective control method for multiple magnetic helical microrobots

Microrobots have been investigated in recent years with the objective of discovering applications in the biomedical industry. The selective control of multiple microrobots is a challenging task; however, such control would allow for the dexterous manipulation of microscale objects. In this paper, we present a novel control method for the selective actuation of microrobots using only an external magnetic field. Such selective actuation of microrobots can be achieved by combining two types of external magnetic field rotations and two microrobotic designs, one with a bar-shaped head and the other with a cross-shaped head. After the type of rotation is chosen, the bar-shaped or the cross-shaped head can be individually actuated or both of them can be actuated simultaneously. To demonstrate the feasibility of the proposed method, millimeter-sized prototypes were fabricated and their individual actuation was successfully demonstrated in silicone oil. The prototypes showed the ability to swim in silicone oil (viscosity: 100 cSt) with a synchronized frequency of up to 0.25 Hz. This result suggests that the proposed method can be used in water at high input frequencies while taking the scaling effect into consideration. Hence, this method is expected to have many practical applications.