Magnetic Lateral Ladder for Unidirectional Transport of Microrobots: Design Principles and Potential Applications of Cells‐on‐Chip

Abstract

Functionalized microrobots, which are directionally manipulated in a controlled and precise manner for specific tasks, face challenges. However, magnetic field‐based controls constrain all microrobots to move in a coordinated manner, limiting their functions and independent behaviors. This article presents a design principle for achieving unidirectional microrobot transport using an asymmetric magnetic texture in the shape of a lateral ladder, which the authors call the “railway track.” An asymmetric magnetic energy distribution along the axis allows for the continuous movement of microrobots in a fixed direction regardless of the direction of the magnetic field rotation. The authors demonstrated precise control and simple utilization of this method. Specifically, by placing magnetic textures with different directionalities, an integrated cell/particle collector can collect microrobots distributed in a large area and move them along a complex trajectory to a predetermined location. The authors can leverage the versatile capabilities offered by this texture concept, including hierarchical isolation, switchable collection, programmable pairing, selective drug‐response test, and local fluid mixing for target objects. The results demonstrate the importance of microrobot directionality in achieving complex individual control. This novel concept represents significant advancement over conventional magnetic field‐based control technology and paves the way for further research in biofunctionalized microrobotics.

Magnetically Selective Versatile Transport of Microrobotic Carriers

“…Based on the geometry designs of micromagnet ladders or negative patterns and in combination with three-dimensional structures as well, the microrobotic carriers can be controlled simultaneously in a specific direction. [24][25][26][27] Furthermore, the introduction of circuit concepts allows for programmable active transport of the microrobotic carriers under a magnetic in-plane field with a combination of current lines or a pulsed out-of-plane field, which can produce instantaneous potential energy for the microrobotic carriers to cross the energy barrier over the micromagnet. A nonmagnetic gap could also cause an energy barrier to hinder particle transportation.…”