Candle Soot as a Template for a Transparent Robust Superamphiphobic Coating

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Science  06 Jan 2012:
Vol. 335, Issue 6064, pp. 67-70
DOI: 10.1126/science.1207115

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  1. Fig. 1

    Morphology of porous structure. (A) Photograph depicting sample preparation. A glass slide is held in the flame of a candle until a soot layer a few micrometers thick is deposited. (B) Scanning electron microscope (SEM) image of the soot deposit. (C) High-resolution SEM image showing a single particle chain made up of almost spherical carbon beads 40 ± 10 nm in diameter. (D) SEM image of the deposit after being coated with a silica shell (see fig. S2 for a cross section of the deposit). (E) High-resolution SEM image of a cluster after the carbon core was removed by heating for 2 hours at 600°C. (F) High-resolution TEM image of a cluster after calcination, revealing the silica coating with holes that were previously filled with carbon particles. The silica shell is 20 ± 5 nm thick.

  2. Fig. 2

    Superamphiphobicity of the surface. A 2-μl water drop (A) and 5-μl hexadecane drop (B) deposited on the surface possess a static contact angle of 165° ± 1° and 156° ± 1°, respectively. (C) Cartoon of a liquid drop deposited on the fractal-like composite interface. (D) Time-resolved images of the bouncing of a 5-μl hexadecane drop on a superamphiphobic surface. Just before impinging, the drop’s kinetic energy exceeds its interfacial energy by 2.4 (that is, the Weber number is 2.4) (28).

  3. Fig. 3

    Thermal stability and light transmittance of a superamphiphobic surface. (A) Static contact and roll-off angles of hexadecane measured after the samples were annealed for 1 hour at various temperatures. The surface loses its superamphiphobicity after annealing at temperatures above 400°C because of thermal degradation of the fluorosilane (shadow area). (B) Ultraviolet-visible transmittance spectra of a 3-μm-thick superamphiphobic surface compared to pristine glass. (C) Photograph of a drop of dyed water (γlv = 72.1 mN/m, blue); peanut oil (γlv = 34.5 mN/m, white); olive oil (γlv = 32.0 mN/m, yellow); and dyed hexadecane (γlv = 27.5 mN/m, red) deposited on a superamphiphobic glass slide. The coated slide was placed on labeled paper.

  4. Fig. 4

    Mechanical resistance quantified by sand abrasion. (A) Schematic drawing of a sand abrasion experiment. (B) Hexadecane drop deposited on the coating after 20 g of sand abrasion from 40 cm height. The 100- to 300-μm-sized grains had a velocity of 11 km/hour just before impingement. After impingement, the drops rolled off after the substrate was tilted by 5°. (C) SEM image of a spherical crater (orange circle) after sand abrasion. (D) SEM image of the surface topography inside the cavity.

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