Su 8 2005 photoresist

Fabrication of PDMS microfluidic devices followed standard rapid prototyping procedures as previously described (18 (link)). The patterns on a silicon wafer for microchannels (4 μm high and 100 μm wide) and nanoslit (450 nm high and 40 μm wide overlayed with 4 μm high and 80 μm wide microchannels were fabricated using soft lithography. The Cr mask was obtained from Amed Inc. (Seoul, Korea). SU-8 2005 photoresist (Microchem, Newton, MA, USA) was spin-coated onto the silicon wafer to make 4 μm high photoresist layer. After spin coating, the baked wafer was exposed under 350 nm irradiation. The patterned wafer was baked again and developed using a SU-8 developer (Microchem). The height was measured by a profilameter (Dektak XT, Bruker). The PDMS pre-polymer mixed with curing agent (10:1 weight ratio) was cast on the patterned wafer and cured at 65° C for 4 h or longer. Cured PDMS was peeled off from the patterned wafer and then PDMS devices were treated in an air plasma generator for 30 s with 100W (Femto Science Cute Basic, Korea) to make PDMS surface hydrophilic. PDMS devices were stored in water and air-dried before use.

Micropatterning for podocytes, smooth muscle cells, and fibroblast cultures were fabricated by conventional photolithography using SU8 2005 photoresist (MicroChem) onto 22 mm × 22 mm microscope cover glass slides (Corning, Cat: 2725–22). Prior to fabrication, glass coverslips were cleaned by sonication in isopropanol and deionized water for 15 min each and then baked in oven at 110 °C overnight. Photolithography was performed on Süss MicroTec MA6 Mask Aligner (Süss Microtec AG, Germany) using standard vacuum hard-contact mode. UV source was a standard mercury lamp with a power throughput of 8 mJ/cm², and exposure time of 115–125 s with 360 nm long pass filter (Omega Optical, SKU: 2007308) was used in order to ensure straight edges and sidewalls.
Following fabrication, patterned slides were treated with pluronic F-127 (Sigma-Aldrich, Cat: P2443). The natural hydrophobicity of SU8 allowed selective adsorption of pluronic only onto the SU8 and not onto the glass substrate, which ensured that cells could only spread within the patterns. Slides were immersed in 1% (wt/vol) pluronic solution for 3 h. Excess pluronic was washed away using deionized water and PBS. The substrates were then immersed in culture media for 1 h and used immediately thereafter.

A standard rapid prototyping method was used to create PDMS microfluidic devices for DNA elongation and deposition on a positively charged surface [51 (link)]. Briefly, the patterns on a silicon wafer for microchannels (2.3 μm high and 100 μm wide) were fabricated using SU-8 2005 photoresist (Microchem, Netonpression, MA, USA). The PDMS pre-polymer mixed with a curing agent (10:1 weight ratio) was cast on the patterned wafer and cured at 65 °C for four hours or longer. Cured PDMS was peeled off from the patterned wafer, and the PDMS devices were treated in an air plasma generator for 1 min with 100 W (Femto Science Cute Basic, Hwaseong, Korea) to alter the PDMS surface to become hydrophilic. The PDMS devices were punctured for an inlet and outlet. The devices were stored in water before use.