title: Twisting microfluidics in a planetary centrifuge.
abstract: This paper reports a twisting microfluidic method utilising a centrifuge-based fluid extruding system in a planetary centrifuge which simultaneously generates an orbital rotation and an axial spin. In this method, fluid extrusion from a micro-scale capillary to an 'open-space' solution or air enables release of the fluid from the capillary-based microchannel, which physically means that there is a release of fluids from a confined low-Reynolds-number environment to an open non-low-Reynolds-number environment. As a result, the extruded fluids are separated from the axial spin of the capillary, and the difference in the angular rates of the axial spin between the capillary and the extruded fluids produces the 'twisting' of the fluid. In this study, we achieve control of the twist of highly viscous fluids, and we construct a simple physical model for the fluid twist. In addition, we demonstrate the formation of twisted hydrogel microstructures (stripe-patterned microbeads and multi-helical microfibres) with control over the stripe pattern and the helical pitch length. We believe that this method will enable the generation of more sophisticated microstructures which cannot easily be formed by usual channel-based microfluidic devices. This method can also provide advanced control of microfluids, as in the case of rapid mixing of highly viscous fluids. This method can contribute to a wide range of applications in materials science, biophysics, biomedical science, and microengineering in the future.
authors.affiliation: Department of Computational Intelligence and Systems Science, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8502, Japan.
authors.forename: Shoya
authors.initials: S
authors.lastname: Yasuda
authors.affiliation: Department of Computational Intelligence and Systems Science, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8502, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Hayakawa
authors.affiliation: Department of Mechanical Engineering, Faculty of Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Onoe
authors.affiliation: Department of Computational Intelligence and Systems Science, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8502, Japan and Department of Computer Science, School of Computing, Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama, Kanagawa 226-8502, Japan. takinoue@c.titech.ac.jp masahiro.takinoue@takinoue-lab.jp.
authors.forename: Masahiro
authors.identifier: http://orcid.org/0000-0002-3874-2670
authors.initials: M
authors.lastname: Takinoue