Transporting macrophages with magnetic helical microrobots

Recent work has shown that microrobots can be used to transport cargo, such as cells, in a targeted manner. Despite abundant proof-of-concept cargo transportation studies, a comprehensive analysis on how the addition of cellular cargo impacts microrobot motion in a fluid environment remains unclear. In this work, we address this gap in knowledge by computationally and experimentally studying how the locomotion of magnetically responsive helical microrobots is altered when transporting macrophages, an immune cell, in the presence of a rotating magnetic field.

Helical microrobots, 50 microns in size, were fabricated with two-photon lithography and coated with chromium, nickel, and titanium to endow magnetic responsiveness in a biocompatible shell. Macrophages were added to the helices and cell attachment was characterized. The locomotion of the cell/microrobot complexes were studied in the presence of a rotating magnetic field.

We found that the location of cell attachment had a deterministic effect on the motion of the microrobot. Cells attached to the ends of the helices had a minor effect on the magnitude and direction of the microrobot velocity compared to cells inside and along the sides of the helices. We explain the alteration to locomotive modes via simulations of microrobot translation and rotation to determine changes in hydrodynamic mobility. This understanding can be leveraged to improve the efficacy of microrobots in biomedical and environmental remediation applications.