Versatile non-contact micro-manipulation method using rotational flows locally induced by magnetic microrobots

We present a versatile non-contact micromanipulation approach using the rotational flows locally induced by rotation of spherical magnetic microrobots in liquid environments. Micro-scale objects in close vicinity to the rotating microrobot are trapped inside the induced rotational flows and carried along with the robot as it translates on a planar surface by rotational motion. The proposed approach can handle a wide range of object sizes, and manipulate objects larger than the robot and significantly denser than water. Trapping and transport of individual human myeloid leukemia cells and swimming flagellated bacteria using this method has also been demonstrated. The proposed approach requires no special surface pattern or spatial structure, and hence is directly compatible with existing microfluidic devices.

I. Introduction

Manipulation of micro-scale objects is an important challenge frequently seen in many research domains including biology, medicine, and chemistry. Such micro-manipulation tasks can be performed in two fashions depending on whether mechanical contact occurs during the process. For contact micro-manipulation, various micro-grippers have been developed which are capable of manipulation with high spatial precision [1]–[3]. However, the conventional micro-grippers are tethered devices, which limits their applications in enclosed environments such as microfluidic chips. Mechanical contact during manipulation may also cause issues such as damage to fragile samples, and stiction between surfaces which makes precise release of samples challenging. On the other hand, non-contact micro-manipulation techniques exert manipulative forces via physical forces without mechanical contact. Hence, they can overcome the disadvantages of contact-based methods and are compatible with current microfluidic devices.