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Can non-linear elasticity explain contact-line roughness at depinning?

Pierre Le Doussal·Kay Joerg Wiese·Elie Raphael·Ramin Golestanian
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Abstract

We examine whether cubic non-linearities, allowed by symmetry in the elastic energy of a contact line, may result in a different universality class at depinning. Standard linear elasticity predicts a roughness exponent zeta=1/3 (one loop), zeta=0.39 (numerics) while experiments give zeta of about 0.5. Within functional RG we find that a non-local KPZ-type term is generated at depinning and grows under coarse graining. A fixed point with zeta=0.45 (one loop) is identified, showing that large enough cubic terms increase the roughness. This fixed point is unstable, revealing a rough strong-coupling phase. Experimental study of contact angles theta near pi/2, where cubic terms vanish in the energy, is suggested.

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Pierre Le Doussal, Kay Joerg Wiese, Elie Raphael, Ramin Golestanian. 2004-12-22. Can non-linear elasticity explain contact-line roughness at depinning?. https://doi.org/10.1103/physrevlett.96.015702

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