Designing superoleophobic surfaces

AEI 83

Anish Tuteja, atuteja@mit.edu1, Wonjae Choi2, Gareth H. McKinley, gareth@mit.edu3, and Robert E. Cohen, recohen@mit.edu1. (1) Department of Chemical Engineering, Massachusetts Institute of Technology, Bldg. NE-47, Room 583, 500 Technology Square, Cambridge, MA 02139, (2) Department of Mechanical Engineering, Massachusetts Institute of Technology, MA, (3) Hatsopoulos Microfluids Laboratory, Department of Mechanical Engineering, Massachusetts Institute of Techology, 77 Massachusetts Ave., Cambridge, MA 02139
The combination of surface chemistry and roughness on multiple scales imbues enhanced repellency to the lotus leaf surface when in contact with a high surface tension liquid such as water. This understanding has led to the creation of a number of biomimetic superhydrophobic surfaces (i.e. apparent contact angles (θ*) with water greater than 150 and low contact angle hysteresis). However, surfaces that display contact angles of θ* > 150 with organic liquids having appreciably lower surface tensions (i.e. superoleophobic surfaces) are extremely rare. Calculations suggest that creating such a surface would require a surface energy lower than any known material. In our recent work (Science, 318, 1618, 2007) we demonstrated how a third factor, re-entrant surface curvature, in conjunction with chemical composition and roughened texture can be used to design surfaces that display extreme resistance to wetting from alkanes such as decane and octane. Here, we extend the work by establishing four design parameters that correlate the solid surface (surface energy and texture) and liquid (surface tension) properties to the observed contact angles with the liquid, as well as, the robustness of the composite interface. This allows for the creation of non-wetting rough surfaces with a given liquid, even though the same liquid easily wets smooth surfaces made from the same material.
 

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The 236th ACS National Meeting, Philadelphia, PA, August 17-21, 2008