Untethered Micromachines Using Magnetic Nanoparticles for Wireless Assembly of Cell-laden Heterogeneous Micromodules

Magnetic micromanipulation has shown huge potential in biomedical research and regenerative medicine, which can be utilized to bio-assemble in-vitro tissues as pharmacological or physiological models. Here, a novel clamp magnetic micromachine was proposed for the assembly of cell-laden micromodules. The magnetic micromachine was fabricated with nickel nanoparticles and polydimethylsiloxane by mold replication. Composed of a through-hole template patterned by chemical etching and a glass substrate coated with an adhesive layer, the multi-layer mold was designed to ensure high resolution and low surface roughness. An eight-coil electromagnetic system was set up to generate a 3D magnetic field of up to 80mT. Driven by external magnetic field and its gradient, the micromachine is able to rotate with a frequency of 3 Hz or translate with a speed of 5 mm/s near the workspace center, which shows lower current supply and higher dynamic response than conventional electromagnetic systems. To evaluate the practicality of the micromachine, cell-laden hydrogel micromodules were assembled by indirect propulsion and integrated into a reconfigurable architecture with heterogeneous shape and composition. We anticipate that this system will regenerate more complex tissues with physiological importance in future tissue engineering.