Experimental Soft Condensed Matter Group Harvard University, Prof. D. A. Weitz Cool Picture of the Moment

Early-time evolution of a gel sample with φ=0.045, ξ=0.059 and c_p=3.31 mg/mL, also illustrated in Fig. 1d. Time elapsed after mixing indicated by the counter in the upper left. Three-dimensional reconstruction (56x56x56μm³) shown at left, with a two-dimensional confocal microscope image at upper right. The static structure factor S(q) is shown as a function of scattering vector q at lower right. Clusters are colored by their mass. After mixing, the sample undergoes spinodal decomposition. Clusters in the sample grow, manifest in S(q) as the growth and narrowing of a peak, which moves to lower q as a function of time. After two hours, all clusters have merged into a single spanning cluster that arrests, forming a gel. The peak in S(q) no longer evolves, and while the spanning cluster fluctuates thermally and exchanges monomers with a sparse colloidal gas phase, no significant structural arrangements occur.

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