Inkjet assisted electroforming and collective actuation of disk-shaped magnetic micromotors

Microrobotic swarms, with their intrinsic ability to multiply the properties of a single device by hundreds or thousands of times, demonstrate great potential for advanced microsurgery, targeted drug delivery or manipulation at the microscale. This is especially true in the case of magnetically actuated swarms, which can be remotely manipulated with high precision also in-vivo. The manufacturing and the collective actuation of a large number of devices, however, is a challenging task and it requires the development of highly tailored, adaptable and low cost strategies. In the present work, we demonstrate that a combination of inkjet assisted lithography (IAL) and electroforming can be a high-throughput, scalable and low-cost fabrication method for the production of disk-shaped ferromagnetic micromotors. Thanks to the versatility of the hybrid manufacturing technique developed, the diameter and the thickness of the devices can be easily controlled and tailored according to the target application. In addition, the use of electroforming makes possible the manufacturing of soft or hard magnetic devices, whose magnetization direction can be programmed. In the specific case, Ni and CoNiP devices were produced, characterized and actuated in swarms composed of hundreds of individuals. According to their magnetic properties, the devices exhibited highly controllable actuation patterns with multiple degrees of freedom. In order to provide an applicative perspective, the ferromagnetic micromotors were coated with polypyrrole and employed for drug delivery, evidencing thus their capability to load and release the model molecule Rhodamine B.