title: Towards combinatorial mixing devices without any pumps by open-capillary channels: fundamentals and applications.
abstract: In chemistry, biology, medical sciences and pharmaceutical industries, many reactions have to be checked by transporting and mixing expensive liquids. For such purposes, microfluidics systems consisting of closed channels with external pumps have been useful. However, the usage has been limited because of high fabrication cost and need for a fixed setup. Here, we show that open-capillary channels, which can be fabricated outside a clean room on durable substrates and are washable and reusable, are considerably promising for micro-devices that function without pumps, as a result of detailed studies on the imbibition of open micro-channels. We find that the statics and dynamics of the imbibition follow simple scaling laws in a wide and practical range; although a precursor film obeying a universal dynamics appears in the vertical imbibition, it disappears in the horizontal mode to make the design of complex micro-channel geometry feasible. We fabricate micro open-channel devices without any pumps to express the green fluorescent protein (GFP) by transporting highly viscous solutions and to accomplish simultaneous chemical reactions for the Bromothymol blue (BTB) solution. We envision that open-capillary devices will become a simple and low-cost option to achieve microfluidic devices that are usable in small clinics and field studies.
authors.affiliation: Department of Physics, Faculty of Science, Ochanomizu University, 2-1-1, Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan.
authors.forename: Marie
authors.initials: M
authors.lastname: Tani
authors.affiliation: 1] Division of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, 2-24-16 Naka-cho Koganei-shi Tokyo 184-8588 Japan [2] Artificial Cell Membrane Systems Group, Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado Takatsu-ku Kawasaki 213-0012, Japan.
authors.forename: Ryuji
authors.initials: R
authors.lastname: Kawano
authors.affiliation: Artificial Cell Membrane Systems Group, Kanagawa Academy of Science and Technology (KAST), 3-2-1 Sakado Takatsu-ku Kawasaki 213-0012, Japan.
authors.forename: Koki
authors.initials: K
authors.lastname: Kamiya
authors.affiliation: Department of Physics, Faculty of Science, Ochanomizu University, 2-1-1, Otsuka, Bunkyo-ku, Tokyo 112-8610, Japan.
authors.forename: Ko
authors.initials: K
authors.lastname: Okumura
mesh_terms: D001979:Bromthymol Blue / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D044085:Microfluidics / Q000295:instrumentation*; D012996:Solutions
chemical_list: D012996:Solutions; D049452:Green Fluorescent Proteins; D001979:Bromthymol Blue