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Design and Construction of a Microfluidic Device for Studying Protein Nucleation and Crystallisation Host Publication: 23rd European Crystallographic Meeting Authors: R. Willaert, C. Vanhee, C. De Tandt, W. Ranson, R. Vounckx and L. Wyns Publication Year: 2006
Abstract: The design and construction of a microfluidic T-mixer is described. In a T-mixer, 2 channels with a small width (50 - 100 µm) are merged into a single channel (100 µm width) in which mixing takes place. In this device, the protein solution and precipitant solution are mixed. Due to the small dimensions of the channels, fluid flow is laminar and mass transport in the mixing channel occurs only by diffusion, normal to the flowing direction. At proper supersaturation values, nuclei will be formed in the mixing channel. These nuclei are allowed to grow into crystals in a metastable condition.
Polydimethylsiloxane (PDMS) microfluidic chips were built using soft lithography. Silicon wafers were coated with Photoresist Shipley AZ 1400ᆹ by spinning 6 different layers on top of each other at 1000 rpm for 30 s on a Headway Research Inc. spincoater. Each Photoresist layer has been seperately soft baked at 90°C for 3 min 30 s. UV exposure through black-and-white transparancy masks was performed for 2 min on a 365nm mask aligner (Karl Suss MJB3). The Photoresist channel mold (total thickness 8.6 - 9 µm) has been developed in Developer 312 (Shipley) in 1:1 ratio for 3min and hard baked on a hot plate at 120°C for 5 min.
PDMS (Sylgard 184, Dow Corning) in 10:1 ratio was poured onto the Photoresist mold in a Petri dish and baked in an 80°C oven for 60 min. Glass coverslips were coated with PDMS (Sylgard 184) in 5:1 ratio spin coated on a glass substrate at 5000 rpm for 60 sec and baked at 80°C during 15 min. The thick PMDS chip was sealed to the coverslip by baking at 80°C for 120 min.
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