Superoleophobic Behavior Induced by Nanofeatures on Oleophilic Surfaces

Abstract

The control of surface wetting properties to produce robust and strong hydrophobic and oleophobic effects on intrinsically oleophilic surfaces is at the heart of many technological applications. In this paper, we explore the conditions to observe such effects when the roughness of the substrate is of fractal nature and consists of nanofeatures obtained by the ion track etching technique. The wetting properties were investigated using eight different liquids with surface tensions gamma varying from 18 to 72 mN m(-1). While it is observed that all the tested oils readily wet the flat substrates, it is found that the contact angles are systematically exalted on the rough surfaces even for the liquids with very low surface tension. For liquids with gamma > or = 25 mN m(-1) an oleophobic behavior is clearly induced by the nanostructuration. For liquids with gamma < 25 mN m(-1), although the contact angle is enhanced on the nanorough surfaces, it conserves its oleophilic character (theta* lower than 90 degrees). Moreover, our experiments show that even in the case of hexane, liquid having the lowest surface tension, the homogeneous wetting (Wenzel state) is never reached. This high resistance to liquid impregnation is discussed within the framework of recent approaches explaining the wetting properties of superoleophobic surfaces.

Superamphiphobic surfaces

“…38 Glass can be 10 tailored by ion etching, and subsequently chemical etching in aqueous HF. 39 Besides the etching techniques discussed above, other etching methods such as plasma etching 40 and water etching 41 can also be applied, depending on the chemical property of the substrate. …”

Polymeric Slippery Coatings: Nature and Applications

“…Oleophobic coatings provide a different kind of slippery surfaces that could resist wetting of water as well as other lower surface tension liquids such as hexadecane, dodecane, octane, and ethylene glycol [22][23][24][25][26][27][28][29][30]. Since such surfaces could repel different kind of liquids, they are considered omniphobic.…”

On-Chip Double Emulsion Droplet Assembly Using Electrowetting-on-Dielectric and Dielectrophoresis

“…[97][98][99][100][101][102][103][104][105][106][107][108] Two well-known models, developed independently by Wenzel [109] and Cassie and Baxter [110], are Branch III corresponds to an inversion of the first branch. All the three branches show that texturing enhances natural wetting property of a surface.…”

“…Methods used to create rough aluminum surfaces include anodic oxidization [98,103], sand-blasting, and electrolytic etching [108]. Nowadays, microstructured surfaces are usually fabricated by microfabrication methods, for example, micro-hoodoo structures on silicon wafer [97], hierarchical silica sphere stacking layers [99], ion track etched silica film [100], and re-entrant structures on PDMS [102]. The bonding of the fluorinated chemical layer is done by either coating [98,102] or chemical vapor deposition (CVD).…”

“…The bonding of the fluorinated chemical layer is done by either coating [98,102] or chemical vapor deposition (CVD). [97,100] A different strategy for making oleophobic surfaces is to add fluorinated compounds to the structure materials before they form microstructured surfaces.…”