Wetting and spreading are ubiquitous in nature and technology. Static wetting, often characterized by the contact angle, is controlled by the balance of at the contact line. Dynamic wetting is more complex since the fluid flow near the contact line causes viscous forces on the interfaces in addition to the capillary forces. These viscous forces become dominant as the contact line is approached. Thus, wetting phenomena we observe and attempt to control on the macroscopic scale are controlled by the physics and chemistry in the microscopic region near the contact line, a region where the static and dynamic behavior of the fluid may be different than in the bulk phase. We study a number of aspects of static and dynamic wetting.

Colloidal dispersions contain small, typically micron scale, solid particles suspended in a fluid. The stability and rheology of these dispersions depend on the forces between the colloidal particles. The particles can often be moved by fields applied to the suspension. In recent years we have investigated two aspects of colloidal forces and the manipulation of particles in electric fields.

Current knowledge is insufficient to reliably predict when a vehicle braking system will squeal. This problem, in common with many others involving friction-induced vibration, remains intractable because of significant shortcomings in the modeling of friction at interfaces. Our ultimate goal is to produce an experimentally verified model that identifies the key variables relevant to producing friction induced vibrations and to determine the sensitivity of the threshold for this vibration to those variables. We ask why in some systems, the friction induced vibration produces the harsh squeal of a brake while on a violin (in the hands of a skilled player) it produces a rich tone.

Our groups seeks projects where we can apply the fundamental knowledge about interfacial physics and chemistry to technological problems. We have undertaken a number of such projects in the past and welcome opportunities to participate in more such projects in the future. Recent project include: