Wetting and Pickering Emulsions: measured receding contact angles on spherical particles as a function of interface shape.

When predicting the effectiveness of particles as droplet stabilizers, one often assumes that the contact angle (advancing or receding) is a property of the materials. We find that, by contrast, the receding angle is sensitive to the interface shape, while the advancing angle remains constant. In particular, we find that the receding angle decreases substantially with increasing anisotropy of the interface shape (parameterized by the deviatoric curvature). Measurements we made with carefully cleaned glass spheres functionalized with PDMS; angles were measured by image analysis and control experiments were done.