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).

Rapid mold-free manufacturing of microfluidic devices with robust and spatially directed surface modifications

“…[15][16][17][18] Hence, protocols suited for small-scale manufacturing are seldom transferrable to larger-scale production, in particular because the available materials differ between small and large-scale productions. In the case of moldfree techniques, surface modification has been reported for SU8, using plasma treatment activation [19,20] or chemical ring-opening of the residual epoxy groups together with amine or silane-based chemistry. [21][22][23] These methods suffer from either short shelf life or long multistep processing.…”

Topographical and Physicochemical Contrast in Photopatterned SU-8 Films for Microfabrication of Multilayer Structures

“…Microposit resist displays better wettability compared to water. Wetting angles for water can be compared with typical values reported in the literature (60 ∘ -80 ∘ ) [31][32][33][34][35]. Water wettability is also important because the majority of developers products for positive tone resist are aqueous based solutions.…”

A multilayered microfluidic system with functions for local electrical and thermal measurements

“…Since SU-8 surface is hydrophobic, the microchannel layer cannot be sealed directly with a PDMS sheet. The samples were treated with oxygen plasma for approximately 30 s at a power about 50 W, which turned the hydrophobic SU-8 surface into a hydrophilic surface (Walther et al 2007(Walther et al , 2010. The top PDMS cover layer was bonded to the oxygen plasma treated SU-8 surface with a double-layer PDMS technique (Prabhakar and Mukherji 2010), where a hot PDMS sheet is used as an adhesive layer.…”