INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF MICROMECHANICS AND MICROENGINEERING J. Micromech. Microeng. 15 (2005) 2156–2162 doi:10.1088/0960-1317/15/11/023 Surface-modified polyolefin microfluidic devices for liquid handling Rongsheng Lin 1,3 and Mark A Burns 1,2 1 Department of Chemical Engineering, The University of Michigan, Ann Arbor, MI 48109-2136, USA 2 Department of Biomedical Engineering, The University of Michigan, Ann Arbor, MI 48109-2136, USA 3 Department of Electrical Engineering, The University of Michigan, Ann Arbor, MI 48109-2136, USA E-mail: maburns@umich.edu Received 3 August 2005, in final form 23 September 2005 Published 10 October 2005 Online at stacks.iop.org/JMM/15/2156 Abstract Polymer-based microfluidic devices offer an attractive platform for single-use disposable applications due to their low cost, ease of fabrication and good biocompatibility. In this work, we investigated liquid handling in surface modified polyolefin microfluidic devices. The modification of the surface was accomplished using ultraviolet light, and the contact angle was reduced from 88 ◦ to 45 ◦ . This type of treatment is easy to implement and could be beneficial for liquid handling in microchannel networks. Capillary-driven flow, contact angle hysteresis and pulsed pumping were demonstrated in these plastic devices. This surface treatment also facilitates rapid gel loading for separation since viscous sieving media can be injected solely by capillary force. Nucleic acid separation was demonstrated in the gel-loaded devices. (Some figures in this article are in colour only in the electronic version) Introduction The development of microfluidic systems for many routine tasks has been a significant area of research in chemistry, biology and medicine in recent years due to the reduction in analysis time and reagent volumes resulting from the miniaturized format. Great strides have been made in applying microfluidics for genomics (DNA genotyping or sequencing) [1–3], proteomics (protein identification) [4–7], and clinical diagnostics (virus or pathogen detection) [8, 9]. However, substrate materials have to be chosen carefully in terms of cost, biocompatibility, mechanical, chemical and optical properties, ease of fabrication and other properties. Much of the initial work on miniaturized chemical analysis systems has centered on the use of glass or silicon substrates along with the standard lithographic fabrication technology [10]. Compared to glass and silicon, polymers are attractive materials ideally suitable for single-use disposable devices since they offer low cost, ease of fabrication and good biocompatibility. There have been increasing efforts to use polymeric materials for chip-based devices. Several extensive reviews have discussed fabrication techniques of polymer microfluidic devices including casting, laser ablation, imprinting, hot embossing and injection molding along with their applications for genetic analysis [11–13]. Various polymeric materials, including poly(dimethylsiloxane) (PDMS), poly(methyl methacrylate) (PMMA) and polycarbonate (PC) have been employed in the fabrication of microfluidic devices. Most of the commercially available polymers for microfluidic applications are hydrophobic. These materials include polycarbonate (PC), poly(methyl methacrylate) (PMMA), polydimethysiloxane (PDMS) and copolymer of 2- norbornene ethylene (‘cyclic olefin copolymer’, COC). The hydrophobic nature could be problematic for liquid handling in microfluidic devices. Unlike loading samples in hydrophilic channels using capillary force, external pumping is necessary to wet hydrophobic channels. As a result of hydrophobic interactions, the surfaces may capture specific compounds from the solution passing through the channels, changing their concentration in the solution and affecting the reliability of quantitative assays. Appropriate functionalization of the surface of the polymer microchannels would enable control 0960-1317/05/112156+07$30.00 © 2005 IOP Publishing Ltd Printed in the UK 2156