Faculty

Associate Professor Darrell Velegol | Research

Fabrication of colloidal devices, nanocolloidal forces and dispersion, nanoscale charge nonuniformity on particles.

Colloidal devices, which are smaller than 10 micrometers in size, have great possibilities in drug delivery, energy collection, micro-robotics, and environmental remediation. We work to fabricate devices for these apaplications from the "bottom-up", meaning that we make "smart parts" that "know" how to piece themselves together. Surface forces control the assembly processes, and so in addition to the engineering applications, we study colloidal forces at a fundamental level. We combine experiments (e.g., video microscopy, Nanofabrication, synthesis, laser trapping), numerics (e.g., Brownian dynamics simulations, eigenmode problems), and theory (e.g., hydrodynamics, elasticity, quantum physics) to reveal how bulk behavior can be controlled using molecular techniques.

Colloidal fabrication

By placing site-specific chemistry on individual colloidal particles using our "particle lithography" method, we are working toward building colloidal machines and devices and patterned particles. Applications include drug delivery, energy, colloidal motors, and environmental.

Nanoscale charge nonuniformity on individual particles

We have developed the technique of "rotational electrophoresis" to measure particle charge nonuniformity for the first time, showing that particles that have long been thought to be uniformly-charged, are in fact not. This has huge ramifications for colloidal forces stability.

Colloidal and nanocolloidal forces and dispersion

We have developed the "coupled dipole method" to calculate van der Waals forces between nanocolloids, to improve upon the Lifshitz theory (which is not applicable for nanocolloids, for several reasons). Then we use our technique of "differential electrophoresis" to measure interparticle forces, for particles as small as 85 nm. The vision is to design nanocolloids that remain stable without dispersants.

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