Liquid Bridges   Leave a comment

Liquid bridges are a volume of liquid held by surface tension between two or more solid supports. You can make them between your fingers the next time you take a bath.

The applications are numerous: oil recovery, crystal growth, granular flow, and an advanced form of transportation technology.

The science is more esoteric, but touches on many deep problems: the shape is a solution to Plateau’s problem and is a minimal surface. The three-phase line, the junction between the liquid bridge/solid support/surrounding fluid, can move (wetting), a process that not understood and in fact violates a foundational principle of fluid mechanics (no slip). If the contact line is pinned by for example, having a solid support with a sharp edge, the contact angle is indeterminate (canthotaxis).

For the most simple solid support geometry- coaxial solid disks of equal size- the stability diagram was solved by Perales and Meseguer in 1992. This was the basis on my PhD research- verifying the stability diagram and extending the experimental parameters to coaxial disks of unequal size, lateral vibrations, and loss of stability to a nonaxisymmetric mode.

The technique we used to image the liquid bridge used principles of Fourier optics- we used a variant of a ‘4f imaging system‘ with a DC stop to block all undiffracted light; the image consisted only of edges (the silhouette of the bridge), allowing for accurate measurements of the dynamic contact angle.

Posted December 27, 2010 by resnicklab

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