Weitz and his group study the physics of soft condensed matter, materials easily deformed by external stresses, electric, magnetic or gravitational fields, and even thermal fluctuations. These materials typically possess structures much larger than atomic or molecular scales; the structure and dynamics at these mesoscopic scales determine the macroscopic physical properties.
The goal of their research is to probe and understand the relationship between mesoscopic structure and bulk properties. The group studies both synthetic and biological materials, with interests ranging from fundamental physics to technological applications and from basic materials questions to specific biological problems.
Techniques used by the group include video-image analysis, light scattering, optical microscopy, rheology, and laser tweezing. New experimental techniques are developed, such as the use of multiply scattered waves to study the dynamics and mechanical properties of materials. Weitz and his group study the properties of colloidal suspensions to investigate the behavior of crystals and glasses as well as the properties of highly disordered gels. They use confocal microscopy, scattering and rheology to investigate both fundamental properties that are modeled using the colloidal particles as well as more technological applications of these systems. They also investigate other soft materials such as foams, emulsions and gels, to study the relationship between their internal structure and dynamics and their bulk properties, developing a fundamental understanding that can also impact on technological applications.
Weitz and his group also are developing methods to make ‘designer’ emulsions and foams on a drop-by-drop basis using a class of microfluidic devices that they have developed. They fabricate multiple emulsions with exquisite precision and they explore both the basic physics of these structures, as well as their potential uses for encapsulation of active materials. In addition, they explore the scale-up of these structures to make useful quantities of materials. Weitz and his group have extensive interactions with industry, with some of their work motivated by the science that directly addresses technologically important problems. In addition, some research in the group has led to promising new technologies, and several start-up companies have emerged from the research.