title: Liquid polystyrene: a room-temperature photocurable soft lithography compatible pour-and-cure-type polystyrene.
abstract: Materials matter in microfluidics. Since the introduction of soft lithography as a prototyping technique and polydimethylsiloxane (PDMS) as material of choice the microfluidics community has settled with using this material almost exclusively. However, for many applications PDMS is not an ideal material given its limited solvent resistance and hydrophobicity which makes it especially disadvantageous for certain cell-based assays. For these applications polystyrene (PS) would be a better choice. PS has been used in biology research and analytics for decades and numerous protocols have been developed and optimized for it. However, PS has not found widespread use in microfluidics mainly because, being a thermoplastic material, it is typically structured using industrial polymer replication techniques. This makes PS unsuitable for prototyping. In this paper, we introduce a new structuring method for PS which is compatible with soft lithography prototyping. We develop a liquid PS prepolymer which we term as "Liquid Polystyrene" (liqPS). liqPS is a viscous free-flowing liquid which can be cured by visible light exposure using soft replication templates, e.g., made from PDMS. Using liqPS prototyping microfluidic systems in PS is as easy as prototyping microfluidic systems in PDMS. We demonstrate that cured liqPS is (chemically and physically) identical to commercial PS. Comparative studies on mouse fibroblasts L929 showed that liqPS cannot be distinguished from commercial PS in such experiments. Researchers can develop and optimize microfluidic structures using liqPS and soft lithography. Once the device is to be commercialized it can be manufactured using scalable industrial polymer replication techniques in PS--the material is the same in both cases. Therefore, liqPS effectively closes the gap between "microfluidic prototyping" and "industrial microfluidics" by providing a common material.
authors.affiliation: Institute of Microstructure Technology (IMT), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany. bastian.rapp@kit.edu.
authors.forename: Tobias M
authors.initials: TM
authors.lastname: Nargang
authors.forename: Lara
authors.initials: L
authors.lastname: Brockmann
authors.forename: Pavel Mitkov
authors.initials: PM
authors.lastname: Nikolov
authors.forename: Dieter
authors.initials: D
authors.lastname: Schild
authors.forename: Dorothea
authors.initials: D
authors.lastname: Helmer
authors.forename: Nico
authors.initials: N
authors.lastname: Keller
authors.forename: Kai
authors.initials: K
authors.lastname: Sachsenheimer
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Wilhelm
authors.forename: Leonardo
authors.initials: L
authors.lastname: Pires
authors.forename: Marian
authors.initials: M
authors.lastname: Dirschka
authors.forename: Alexander
authors.initials: A
authors.lastname: Kolew
authors.forename: Marc
authors.initials: M
authors.lastname: Schneider
authors.forename: Matthias
authors.initials: M
authors.lastname: Worgull
authors.forename: Stefan
authors.initials: S
authors.lastname: Giselbrecht
authors.forename: Christiane
authors.initials: C
authors.lastname: Neumann
authors.forename: Bastian E
authors.initials: BE
authors.lastname: Rapp
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry* / Q000528:radiation effects; D002460:Cell Line; D049109:Cell Proliferation; D002470:Cell Survival; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D005347:Fibroblasts / Q000166:cytology*; D006358:Hot Temperature; D008027:Light; D008422:Materials Testing; D051379:Mice; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D009570:Nitriles / Q000737:chemistry; D044367:Phase Transition / Q000528:radiation effects; D010720:Phosphines / Q000737:chemistry / Q000528:radiation effects; D055668:Photochemical Processes; D017319:Photosensitizing Agents / Q000737:chemistry / Q000528:radiation effects; D011137:Polystyrenes / Q000737:chemistry* / Q000528:radiation effects; D066330:Printing, Three-Dimensional; D014783:Viscosity
chemical_list: D001672:Biocompatible Materials; D004129:Dimethylpolysiloxanes; D009570:Nitriles; D010720:Phosphines; D017319:Photosensitizing Agents; D011137:Polystyrenes; C013830:baysilon; C004526:azobis(isobutyronitrile)