| If one adds a small amount of water to a heap of sand, the medium becomes paste-like since some of the grains get connected by liquid bridges. These bridges act as little springs between neighbouring particles stiffening the material. Hence, we can easily sculpture, for example, a sand castle with wet sand. We use a non-Brownian suspension of micrometer-sized glass spheres dissolved in a critical binary liquid mixture. The suspending water-lutidine mixture exhibits a lower critical point leading to a phase separation slightly above ambient temperature. The water-rich phase wets the glass spheres and liquid bridges are formed upon increasing the temperature within the two-phase region. We study this temperature-induced formation of liquid bridges using a confocal microscope and calculate the cohesive forces from brightfield images. |
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