Thin films superhydrophobic coatings

Another widely used approach in this area is a sol-gel process. In order to create surface roughness after deposition of thin films, a secondary component is included in the sol-gel deposition process which can be removed later by dissolution in hot water or sublimation. The removal of the secondary components gives porous structures. Subsequent lluorinated silane coating can render these sol-gel processed films superhydrophobic [81-83]. Microporous structures can be created through phase separation of organic polymer solutions and then used as a template for sol-gel processing of porous silica substrates. Ruorosilane treatment of these substrates produces superhydrophobic surfaces [84]. 

Here, we employed polymethacrylates to provide the roughened and oxidized surface of aluminium sheets with superhydrophobic properties. Polymethacrylates can be easily synthesized and their properties varied by copolymerization of methacrylate monomers that have different side chains. The correlation between the structural composition of polymethacrylates and their wetting behavior is well known from model studies carried out on thin films on smooth surfaces [19, 20], but there is no information about the wetting behavior of polymethacrylate hlms on micro-rough surfaces. We have synthesized poly(tert-butyl methacrylate) and poly(methyl methacrylate) containing different hydrophobic and hydrophilic sequences. In dependence on the polymer composition the wetting behavior was studied on polymer-coated smooth silicon wafers and rough aluminium surfaces. 

Here we describe two simple fabrication processes to modify the surface of the device to achieve a very high water contact angle. In the first approach, the device was first coated with a thin film of hydrophobic materials, fluoropolymer in this case, and then oxygen plasma was used to create superhydrophobic surfaces. However, only in some cases, the chemical properties of the hydrophobic materials could be altered by the oxygen plasma treatment [19]. Therefore, a second technique has been developed where the nanostructures can be created on the device surfaces by a nanoimprint process [20]. Both of these approaches are compatible with the micro-fabrication process. 

An alternative approach to fabricate a superhydrophobic surface on a device is to utilize the nanoimprint technique to create nanostructures on the chip surfaces, which are coated with a thin film of hydrophobic materials. The fabrication scheme for a superhydrophobic surface using nanoimprint is illustrated in Fig. 2. To conduct nanoimprint lithography, the first step is to fabricate the stamp for nanoimprint. Previously [24-26], we demonstrated a simple technique to fabricate nanoimprint stamp by nanosphere lithography. In this process, a monodispersed polystyrene dispersion with 400 nm diameter beads (Bangs Laboratories, Inc., Fishers, IN) was... 

Huang, L., Lau, S., Yang, H., Leong, E., Yu, S., Prawer, S. (2005). Stable superhydrophobic surface via carbon nanotubes coated with a ZnO thin film. The Journal of Physical Chemistry B, 109, 7746-7748. 

Lee, J.-H., Lee, S.H., Kim, D., Park,Y.S., 2013a. The structural and surface properties of carbon nanotube synthesized by microwave plasma chemical vapor deposition method for superhydrophobic coating.Thin Solid Films 546, 94. 

Stability attributed to the presence of long and thin nanohairs on the fibers (Shin et al., 2012). In another example, inherent microstructure of cellulose paper was enhanced by plasma-assisted nanostructuring to create a surface that once coated with a thin fluorocarbon film was superhydrophobic (Balu et al., 2008).The nanotopography was varied with plasma treatment, yielding a surface in either the Wenzel or Cassie—Baxter states. 

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