Synthesis of hydrophilic to superhydrophobic SU8 surfaces

Abstract

In published literature, it is widely reported that the plasma treatment and funtionalization with Octadecyltrichlorosilane (OTS) self-assembled monolayer (SAM) can individually alter the wetting properties of SU8 surface. A combination of the two approaches gives better results and the synergism of the two approaches produces a superhydrophobic SU8 surface, which is presented in this work. We have investigated various composition of plasma for treatment of SU8 surfaces and permuted the treated SU8 surfaces with deposition of OTS SAM. In all such synergized experiments, we obtained water contact angle higher than 150 , which is much higher than the one that can be obtained with individual application of the two approaches. The combined approach presented in this work is suitable for bulk production of superhydrophobic surface, and is a mask-less process, which makes it cost effective. The surface topography, wetting, and chemical properties of SU8 surfaces were characterized using the contact angle goniometry, atomic force microscopy, FTIR, Raman, and XPS spectra. The superhydrophobic SU8 surfaces were observed to be stable even after five months. EXPERIMENTAL Substrate PreparationSingle side polished p-type silicon wafers (100) were used as substrate. SU8 (Microchem, SU8-2002) negative photo resist were used for experiments. The silicon wafers were cleaned in H 2 SO 4 (98%) and H 2 O 2 (30%) mixture of 3:1 ratio for 15 min to remove organic contaminations. The samples were rinsed thoroughly with DI water followed by drying with nitrogen gas. After cleaning, the SU8 photoresist was spin coated at 500 rpm Additional Supporting Information may be found in the online version of this article.

Roll‐to‐roll nanoimprint lithography of ultrafiltration membrane

“…A dependence of fouling on membrane surface roughness has been experimentally and theoretically observed. [6][7][8] These studies focused on randomly rough surfaces, but recent research has found a correlation between fouling resistance and induced regular surface roughness. [9][10][11] Through use of nanoimprint lithography (NIL)-a process by which submicron patterns are transferred from a mold to a resist by means of mechanical deformation-commercial polyethersulfone (PES) UF membranes were imprinted with regular line and groove surface patterns.…”

Programmable droplet actuating platform using liquid dielectrophoresis

“…The oil treatment is an alternative method to enhance the hydrophobicity of the surface to minimise the contact angle hysteresis, and similar results may also be obtained using an enhanced OTS surface with superhydrophobic wetting properties [19]. The actuation of DI water droplets was achieved at a voltage as low as 30 V when a layer of mineral oil with an average thickness of 100 µm covered the device.…”

Wireless Acoustic-Surface Actuators for Miniaturized Endoscopes

“…When a dried active surface is immersed under water, air is trapped in the cavities as bubbles due to the small size of the cavity and the hydrophobicity of the SU-8 photoresist (∼90° contact angle 27 ). The diameter of the bubble is the same as that of the cavity and the length is normally shorter than that of the cavity, as shown in the inset of Figure 2 .…”