黑料福利网

We follow how small particles respond to forces, in liquid and in air. In liquids, our experiments have uncovered the origins of exclusion-zone (EZ) formation, a previously unexplained effect where particles exhibit long-range repulsion from a solid surface. We have shown that this effect is due to a phoretic force, in this case diffusiophoresis, the transport of colloidal particles along a gradient of (salt) concentration in the background liquid. In liquids, we employ such phoretic forces for applications; we have used electrophoresis and electro-osmosis to control particle transport in nonpolar liquids, which can be used to create faster switching in electronic-paper displays. In air, we use both inertial and electrostatic forces to transport and concentrate aerosol particles in a detection area. We did this earlier for pollen particles, and we now work on monitoring ultrafine particles (UFPs), where we employ nanophotonic fiber-tip optical sensors to detect individual UFPs.

To both study and control how soft materials organize, we build simple microfluidic tools: A recent example is an oil-free platform that enables the controlled formation of two-phase systems (water-in-water droplets) and other phase-separating materials in situ, where tuning the chemistry and channel geometry lets us steer how they exchange, compartmentalize, and reorganize over time. We have already demonstrated this on model PEG-dextran mixtures and on coacervates, and we continue to use the platform to better understand complex phase separation in both synthetic and biological systems.