title: Surface modification method of microchannels for gas-liquid two-phase flow in microchips.
abstract: A capillarity restricted modification method for microchannel surfaces was developed for gas--liquid microchemical operations in microchips. In this method, a microstructure combining shallow and deep microchannels and the principle of capillarity were utilized for chemical modification of a restricted area of a microchannel. A hydrophobic--hydrophilic patterning in microchannels was prepared as an example for guiding gas and liquid flows along the respective microchannels. Validity of the patterning was confirmed by measuring aqueous flow leak pressure from the hydrophilic microchannel to the hydrophobic one. The leak pressure of 7.7-1.1 kPa agreed well with that predicted theoretically from the Young-Laplace equation for the microchannel depth of 8.6-39 microm. In an experiment to demonstrate usefulness and effectiveness of the method, an air bubble was first introduced into the hydrophilic microchannel and purged from the hydrophobic-hydrophilic patterned microchannels. Next, the patterning structure was applied to remove dissolved oxygen by contacting the aqueous flow with a nitrogen flow. The concentration of dissolved oxygen decreased with contact time, and its time course agreed well with numerical simulation. These demonstrations showed that the proposed patterning method can be used in general microfluidic gas-liquid operations.
authors.affiliation: Department of Applied Chemistry, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-8656, Japan.
authors.forename: Akihide
authors.initials: A
authors.lastname: Hibara
authors.forename: Shinobu
authors.initials: S
authors.lastname: Iwayama
authors.forename: Shinya
authors.initials: S
authors.lastname: Matsuoka
authors.forename: Masaharu
authors.initials: M
authors.lastname: Ueno
authors.forename: Yoshikuni
authors.initials: Y
authors.lastname: Kikutani
authors.forename: Manabu
authors.initials: M
authors.lastname: Tokeshi
authors.forename: Takehiko
authors.initials: T
authors.lastname: Kitamori
mesh_terms: D001696:Biomechanical Phenomena; D001709:Biotechnology / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D005740:Gases; D057927:Hydrophobic and Hydrophilic Interactions; D046208:Microchip Analytical Procedures / Q000379:methods*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D036103:Nanotechnology; D009584:Nitrogen / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D011312:Pressure; D012212:Rheology; D012984:Software; D013499:Surface Properties
chemical_list: D005740:Gases; D009584:Nitrogen; D010100:Oxygen