Photopolymerization of a perfluoropolyether oligomer and photolithographic processes for the fabrication of microfluidic devices Alessandra Vitale a,⇑ , Marzia Quaglio b , Matteo Cocuzza a,b,c , Candido Fabrizio Pirri a,b , Roberta Bongiovanni a a Materials Science and Chemical Engineering Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy b Center for Space Human Robotics, Italian Institute of Technology, Corso Trento 21, 10129 Torino, Italy c CNR-IMEM, Parco Area delle Scienze 37a, 43124 Parma, Italy article info Article history: Received 18 November 2011 Received in revised form 11 March 2012 Accepted 18 March 2012 Available online 27 March 2012 Keywords: Microfluidics Perfluoropolyethers Photolithography Photopolymerization Solvent resistance abstract A perfluoropolyether based photocured polymer is proposed as structural material for the fabrication and easy prototyping of microfluidic devices. The kinetics of photopolymeriza- tion and the fluoropolymer characterization is reported, assessing the suitability of the material: it results transparent, thermally resistant, with a good dimensional stability and a chemical resistance much higher than polydimethylsiloxane, material currently used in microfluidics. The direct fabrication of microchannels is finally presented by direct pho- topolymerization under UV light irradiation through photomasks: the transfer of micropat- terns was successful. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Microfluidics represents an emerging technology in many areas of biotechnology and chemistry to achieve, among the other advantages, reduction of reagent vol- umes, improved performances, integration, and parallelism [1,2]. In recent years polymers have assumed a leading role as substrate materials for the fabrication of microfluidic devices. In particular, polydimethylsiloxane (PDMS) has rapidly become a reference material for different applica- tions, thanks to simpler and less expensive fabrication pro- cedures as well as its interesting properties (optical transparency, durability, low cost, biocompatibility, non- toxicity and stability over a wide temperature range) [3–5]. However, extensive application of PDMS in the fields of chemistry and life science is limited due to its low chem- ical resistance. Its incompatibility with many solvents and reagents causes swelling and chemical etching, effects that are even more pronounced in microscale channels due to the high surface to volume ratio. These drawbacks lead to clogging of microchannels, device damaging and delam- ination, contamination of reactions and assays [6,7]. A tre- mendous benefit could therefore come from the development of polymeric devices that offer the same advantages as PDMS microfluidics with the additional fea- ture of high solvent resistance. Such a technology has the potential to expand the field of highly integrated microflui- dics to many new applications in chemical synthesis and analysis, currently of great interest for chemical produc- tion and drug discovery. Perfluoropolyethers (PFPEs) can be an interesting alter- native to PDMS: they typically contain one or two of the repetitive units –CF 2 O–, –CF 2 CF 2 O–, –CF 2 CF 2 CF 2 O–, –CF (CF 3 )CF 2 O– and show high thermal and chemical resis- tance, low refractive index and very low surface tension [8]. Perfluoropolyethers bearing chemically reactive end groups have also been obtained and find applications as elastomers, coatings and surface-treatment agents for tex- tile and paper [9–14]. Acrylates and methacrylates deriva- 0014-3057/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.eurpolymj.2012.03.016 ⇑ Corresponding author. Tel.: +39 0110904656; fax: +39 0110904699. E-mail address: alessandra.vitale@polito.it (A. Vitale). European Polymer Journal 48 (2012) 1118–1126 Contents lists available at SciVerse ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj