Polymer-Based Magnetically Driven Microtool for On-Chip Particle Sorting

We succeeded in powerful noncontact actuation of magnetically driven microtool (MMT) by magnetizing it and focusing magnetic field in a microfluidic chip. Novelty of this paper is summarized as follows. (1) We employed neodymium powder as the main component of MMT. The density of magnetic flux was improved about 100 times larger after magnetization. (2) We fabricated a pair of magnetic sharp needles in the chip by electroplating. MMT was placed between the needles and the density of magnetic flux was improved about 3 times larger. As a result, we succeeded in powerful actuation of MMT in a chip. Drive frequency was improved about 10 times faster (up to 180 Hz). We applied it for sorting of copolymer beads in a chip. The concept of the sorting chip is shown. MMT is put in the microchannel. The principle of the actuation method is also shown. The size of the bead was measured by image processing (15 Hz). Moving frequency of the MMT was made higher than the sampling frequency of measurement and secure sorting was achieved.