Self-Assembly Magnetic Chain Unit for Bulk Biomaterial Actuation

Abstract

Untethered microrobot has been regarded as one of the most powerful tools for performing specific in vitro/vivo tasks, especially magnetic actuated microrobot owing to its biocompatible energy source. However, although numerous design and fabrication technologies of magnetic microrobot have been developed, the improvement of magnetic actuation manner reaches the limit, which mainly relies on the specific structure design (helix) or strong gradient magnetic field to realize locomotion. Inspired from surface cilia dependent paramecium swimming, this letter reports a new self-assembly magnetic actuation concept design for bulk biomaterial motion based on the partial asymmetrical heterofunction of magnetic chain units. Compared with the existing design and fabrication of magnetic microrobot actuators, our proposed self-assembly magnetic chain unit method is succinct, economical, structure unconstrained, and material unconstrained. In this work, the tanglesome bulk fiber fabrication based on flow-focusing microcapillary system is first introduced, which is utilized for structure unconstrained and material unconstrained actuation demonstration. Second, the six degrees of freedom electromagnetic coil system is proposed for presenting the magnetic actuation based on self-assembly magnetic chain units. After that, the self-assembly mechanism and magnetic control mechanism are developed to explain the fabrication and actuation procedure. Finally, the self-assembled magnetic chain units can achieve up to 150 $\mu$ m length during the fabrication process, which can actuate bulk biomaterial with much larger size than itself. The self-assembly magnetic chain unit and actuation experimental results verify the feasibility and practicability of the above-mentioned concepts. This research opens new prospects for magnetic microrobot actuation, which is expected to advance the biomedical area, such as for in vitro/vivo targeted therapy and organ-on-a-chip research.