On-chip micromanipulation using a magnetically driven micromanipulator with an acoustically oscillating bubble

• A new type of magnetically driven micromanipulator for biological and microscale object manipulation is presented and experimentally verified.
• 2D motion control of the micromanipulator (horizontal, vertical, and rotational motions) is carried out by using an external magnetic controller.
• Micro-object manipulation is separately investigated by using an acoustically oscillating bubble.
• The proposed micromanipulation technique can be applied to cell manipulation, micro-assembly, etc.

This paper presents a magnetically driven micromanipulator for biological and microscale (bio/micro-) object manipulation in a microfluidic chip. The proposed micromanipulator mainly consists of a gaseous bubble that functions as a gripping tool and twin permanent magnets allowing for two-dimensional (2D) motion control in an aqueous medium. First, the 2D motion control of the micromanipulator (horizontal, vertical, and rotational motions) was demonstrated by using an external magnetic controller attached to the bottom of the chip, capable of altering the interaction forces induced by twin magnets installed inside both the micromanipulator and controller. Second, the micro-object manipulation was separately tested with glass beads (100 μm diameter) and steel balls (600 μm diameter) using an acoustically oscillating bubble. When the bubble was acoustically excited around its natural frequency by a piezoactuator, the radiation force generated from it attracted neighboring objects. The capturing force generated from an acoustically excited bubble was indirectly measured using the glass beads in a mini-channel. The maximum capturing force occurring at the natural frequency of the bubble was approximately 390 nN. Finally, the manipulation of the steel balls on a chip was achieved with the use of both the magnetic and acoustic actuation. This micromanipulation technique can be applied to cell manipulation, micro-assembly, etc., with the advantage of minimizing any contact damage through the use of the bubble.