People

David A. Weitz
Pierce 231 • 29 Oxford Street
Cambridge, MA 02138
(617) 496-2842

  • Mallinckrodt Professor of Physics and Applied Physics
  • Director of the Materials Research Science and Engineering Center
  • Co-Director of the BASF Advanced Research Initiative
  • Member, Kavli Institute for Bionano Science & Technology

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.

The group also develops drop-based microfluidics for biophysics and biotechnology applications.  This is a microfluidic technique where minute drops immersed in an inert carrier fluid are used as reaction vessels of only a few picoliters in volume.  They are used to collect biological data at very high rates, and Weitz and his group are applying them to investigate issues in biology and for biotechnology applications.

The group also investigates the mechanical properties of biopolymer networks, both model, reconstituted networks, and those in cells, with a goal of understanding mechanical behavior at the level of single cells and of tissue.  They investigate the properties of reconstituted networks of actin, microtubules and intermediate filaments, and study ‘active’ networks, where molecular motors induce active motion.  These studies provide insight into the mechanical properties of cells. They also investigate mechanical properties of extracellular biopolymer networks, including collagen and fibrin.

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.