Soft Matter and Complex Systems Seminar

During the last decade microfluidics has emerged as a powerful tool in synthesis of new materials based on flow-assisted self-assembly of microscopic droplets into compact structures. So far, the efforts focused mainly on assembling small clusters consisting of two-, three-, sometimes several segments for applications in synthesis of non-spherical colloidal particles or multi-compartment capsules. Here, we attempt to formulate much larger structures built of hundreds or thousands of close-packed droplets and discuss their statistical-physical properties. We generate both spheroidal 3D aggregates in which the droplets can be treated an effective soft-solid material as well as elongated, discrete quasi-1D structures formed by repetitive folding of linear chains of droplets in the external co-flow. In the latter case we reveal that the average frequency of folding self-adapts to the rate of external flow while the large-scale fluctuations in the folding frequency are suppressed (as compared to those resulting from uncorrelated Gaussian fluctuations) via a memory effect which we associate with long-range elastic interactions in the chain. With this we demonstrate first experimental example of a self-assembling 1D system developing hyperuniformity (suppressed long-range fluctuations). Finally, we also discuss dynamic instabilities of such structures including chain scission and avalanche-like folding, and develop corresponding stability diagrams.