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Colloids are particles that have a diameter of between approximately 1 and 1,000 nanometres and that are evenly dispersed in fluids. Colloids are also known as colloidal dispersions because the particles remain dispersed and don't settle to the bottom.
Thermal gradients are shown to provide a robust and chemically specific driving force to liposomes. Here the authors show controlled direction of migration of unilamellar lipid vesicles by varying the temperature in the suspension and the exposed polar lipid head groups.
Solid-solid transitions between different crystalline structures have broad implications in earth science, steel and ceramic materials. Peng et al. show a transformation pathway that starts off as being martensitic then switches to diffusive at the single particle level in a colloidal system under pressure.
Conductive colloidal chains are promising for electronics but difficult to synthesize outside of a liquid environment. Here, the authors use field-directed assembly and capillary effects to pull conductive particle chains out of a suspension, which remain held together by flexible liquid bridges even after the external field is turned off.
Water treatment processes mostly rely on the use of membranes and filters, which have high pumping costs and require periodic replacement. Here, the authors describe an efficient membraneless method that induces directed motion of suspended colloidal particles by exposing the suspension to CO2.
Ensembles of magnetic colloids can undergo an instability triggering the formation of clusters that move faster than the particles themselves. The many-body process relies on hydrodynamics alone and may prove useful for load delivery in fluidics.
Confocal microscopy and computational analysis, now used for measuring microscale stresses in colloidal crystals, could be developed for investigation of amorphous materials, crystal melting, and mechanical properties of tissues.
Simple models have given us surprising insight into how animals flock, but most assume they do so through a homogeneous landscape. Colloidal experiments now suggest that a little disorder can have unexpected — and spectacular — effects.