When a small amount (less than 1%) of a second immiscible liquid is added to the continuous phase of a suspension, the rheological properties of the mixture are dramatically altered from a fluid-like to a gel-like state or weakly elastic to strongly elastic state. The yield stress and viscosity increase by several orders of magnitude as the volume of the second fluid increases. This transition is attributed to the capillary forces of the two fluids on the solid particles, and in an analogy to wet granular materials, two distinct states are defined: the "pendular state" where the secondary fluid preferentially wets the particles; and the "capillary state" where the secondary fluid wets the particles less well than the primary fluid. Capillary suspensions are a new class of materials that can be used to create tunable fluids, stabilize mixtures that would otherwise phase separate, and to create new materials such as low-fat foods or microporous solids.

Refreshments will be available starting at 1:45 pm.