8th Liquid Matter Conference September 6-10, 2011 Wien, Austria ...

P7.32Thu 811:10-14:00Capillary filling in patterned microchannelsDavide Ferraro, 1 Tamara Tòth, 1 Matteo Pierno, 1 and Giampaolo Mistura 11 Dipartimento di Fisica - Università di Padova, Via Marzolo, 8, 35131, Padova,ItalyIn the recent years, the capillary filling of microdevices patterned with posts or ridges has beenthe subject of an intense work motivated by the rich phenomenology observed in numericalsimulations [1,2,3] and by its technological interest, like for instance the design of micro-injectionmolding in capillaries [4] and of channel geometries preventing air bubbles during the first stagesof filling in microfluidic chips [5]. Here we present a systematic work aimed to investigate theshape of the air/water meniscus moving in channels micropatterned with different geometric posts.The microchannels are produced by replica molding in PDMS (hydrophobic) and in NOA-61, athiolenic resin slightly hydrophilic, in order to explore surface walls with different wettabilityconditions. The masters for the replica molding are made in SU-8 by standard photolithographictechniques. The cross-section of the channels was about of 100 x 100 µm. By means of amicrofluidic controller we performed measures of the meniscus shape trough a suitable opticalsetup in proximity of symmetric and asymmetric posts as a function of the characteristic size,surface wettability and pressure applied along the channel, comparing our results with thoseobtained in numerical simulations.[1] H. Kusumaatmaja, C. M. Pooley, S. Girardo, D. Pisignano, J. M. Yeomans, PhysicalReview E 77, 067301 (2008).[2] S. Chibbaro, E. Costa, D. I. Dimitrov, F. Diotallevi, A. Milchev, D. Palmieri, G. Pontrelli, S.Succi, Langmuir 25 (21), 12653-12660 (2009).[3] B. M. Mognetti, J. M. Yeomans, Soft Matter 6, 2400-2402 (2010)[4] D. S. Kim, K-C. Lee, T. H. Kwon, S. S. Lee, J. Micromech. Microeng. 12, 236-246 (2002).[5] F. Goldschmidtboeing, M. Rabold, P. Wojas, J. Micromech. Microeng. 16, 1321-1330 (2006).32