Superoleophobicity

To elucidate the origin for the observed superoleophobicity, FOTS pillar array surfaces with (a) a smooth straight sidewall and (b) a straight sidewall with an overhang structure were fabricated (Fig. 4.27). The wetting properties with water and hexadecane were examined and key sessile drop data are included in the figure. The 

Also included in Fig. 4.29a, b are results from pillar array surfaces with 1 and 5 pm diameter pillars (represented by data points X and O, respectively). These data points are completely compatible with the results of the 3 pm pillar array surfaces, indicating that surface adhesion and drop mobility are governed primarily by the density of the contact lines, not the geometry of the texture. 

In summary, we show wifli model pillar array surfaces that hydrocarbon oils can trap air pockets on rough surfaces and result in a Cassie-Baxter composite interface when the following basic parameters are met high hexadecane contact angle surface 

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Saraf, R., Lee, H. J., Michelsen, S., Owens, J., Willis, C., et al 2011. Comparison of three methods for generating supeihydrophobic, superoleophobic nylon nonwoven surfaces. Journal of Materials Science, 46,5751-60. 

As mentioned above, the superhydrophobic-material-based oil/water separation device faces the practical issue that water is usually heavier than oil, which limits the productivity during the separation process. It is thus rational to develop a separation device on the basis of superhydrophilic materials. Among all the superhydrophilic materials, hydrogels exhibit the most robust underwater superoleophobicity and therefore, they are the most ideal candidates for such separation systems. 

Steele, A., Bayer, L, and Loth, E. 2009. Inherently Superoleophobic Nanocomposite Coatings by Spray Atomization. Nano Lett. 9 501. 

H. Zhao, K-Y. Law and V. Sambhy, Fabrication, surface properties, and origin of superoleophobicity for a model textured surface, Langmuir 27, 5927-5935 (2011). 

If a surface or coating also displays such high liquid repellency for oil droplets, it is referred as superoleophobic. Surfaces that display both superhydrophobicity and superoleophobicity and can also repel most other liquids in the same fashion are generally referred to as superomniphobic. Ihe enormous research interest in liquid repellent smfaces stems from their potential to be incorporated in a vast number of different applications [6-17]. 

In general, most superhydrophobic, superoleophobic, and superomniphobic surfaces are very fragile (i.e. they will lose liquid repellency if touched or rubbed by human hands) and are not suitable for commercial uses. This mechanical fragility of the surface texture can cause surface defects which leads to collapse of the Cassie-Baxter state. As a result, a subsequent... 

A.K. Kota, J.M. Mabry and A. Tuteja. Superoleophobic surfaces Design criteria and recent studies. Surface Innovations, 1,71-83 (2013). 

Superhydrophobic and superoleophobic nanostructured aerogel membranes on water or oils... 

Figure 10.15 Underwater superoleophobicity of the microhaired wood-based surface treated with argon plasma (0.2 mbar, 30 W, 120 s). (a) Schematic of the underwater contact angle measurement. Water trapped between microhairs limits the contact between oil and solid, (b) Photograph of a 7 pi oil droplet deposited under water on the plasma-treated microhaired surface with the oil contact angle of 157° [21].

M. N. Kavalenka, A. Hopf, M. Schneider, M. Worgull and H. Holscher, Wood-based microhaired superhydrophobic and underwater superoleophobic surfaces for oil/water separation RSCAdv., 4,31079-31083 (2014). 

T. Darmanin, F. Guittard, S. Amigoni, E. Taffin de Givenchy, X. Noblin, R. Kofman and F. Celestini, Superoleophobic behavior of fluorinated conductive polymer films combining electropolymerization and lithography, Soft Matter, 7, 1053-1057 (2011). 

H. Bellanger, T. Darmanin and F. Guittard, Surface structuration (micro and/ or nano) governed by the fluorinated tail lengths toward superoleophobic surfaces, Langmuir, 28,186-192 (2012). 

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