title: A photoinduced nanoparticle separation in microchannels via pH-sensitive surface traps.
abstract: A microfluidic surface trap was developed for capturing pH-sensitive nanoparticles via a photoinitiated proton-releasing reaction of o-nitrobenzaldehyde (o-NBA) that reduces the solution pH in microchannels. The surface trap and nanoparticles were both modified with a pH-responsive polymer-poly(N-isorpopylacylamide-co-propylacrylic acid), P(NIPAAm-co-PAA). The o-NBA-coated microchannel walls demonstrated rapid proton release upon UV light irradiation, allowing the buffered solution pH in the microchannel to decrease from 7.4 to 4.5 in 60 s. The low solution pH switched the polymer-modified surfaces to be more hydrophobic, which enabled the capture of the pH-sensitive nanobeads onto the trap. When a photomask was utilized to limit the UV irradiation to a specific channel region, we were able to restrict the particle separation to only the exposed region. Via control of the UV irradiation, this technique enables not only prompt pH changes within the channel but also the capture of target molecules at specific channel locations.
authors.affiliation: Department of Bioengineering, University of Washington, Seattle, Washington 98195, United States.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Ebara
authors.forename: John M
authors.initials: JM
authors.lastname: Hoffman
authors.forename: Allan S
authors.initials: AS
authors.lastname: Hoffman
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Stayton
authors.forename: James J
authors.initials: JJ
authors.lastname: Lai
mesh_terms: D001547:Benzaldehydes / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation; D053758:Nanoparticles / Q000737:chemistry*; D055668:Photochemical Processes; D011108:Polymers / Q000737:chemistry; D013499:Surface Properties; D014466:Ultraviolet Rays
chemical_list: D001547:Benzaldehydes; D011108:Polymers; C043850:2-nitrobenzaldehyde