Surface hydrophilization of SU‐8 by plasma and wet chemical processes

Abstract Wetting properties and surface roughness of SU‐8 can be modified by wet chemical and plasma processes. These processes result in an enhanced wettability that can be attributed to an increase of CO and COO groups at the surface. Wet chemical etching with ceric ammonium nitrate (CAN) rendered the SU‐8 surface hydrophilic. However, it also led to the accumulation of cerium species on the surface, which may interfere with biochemical reactions in the device. Surface activation could also be achieved with a low‐temperature atmospheric argon plasma, which left a smooth surface. Treatment of SU‐8 with oxygen plasma led to a stable hydrophilization and an increased surface roughness. Owing to oxygen plasma processing, antimony species were accumulated which could be removed with a cleaning step. In order to maintain the hydrophilization after oxygen plasma treatment for storage, or over several wetting cycles, the surface can be coated with a protein‐resistant graft copolymer (PLL‐ g ‐PEG). Copyright © 2010 John Wiley & Sons, Ltd.