This talk will describe the behavior of fluids flowing through channels of microns in scale and will consider the effects when multiple fluids are present, so interfacial effects become important. Several different phenomena will be described, where the experimental observations are clear, but where a full understanding of the fluid behavior remains elusive.

David A. Weitz (born in 1951) is a Canadian/American physicist and Mallinckrodt Professor of Physics & Applied Physics and professor of Systems Biology at Harvard University. He is the co-director of the BASF Advanced Research Initiative at Harvard, and director of the Harvard Materials Research Science & Engineering Center. He is best known for his work in the areas of diffusing-wave spectroscopy, microrheology, microfluidics, rheology, fluid mechanics, interface and colloid science, colloid chemistry, biophysics, complex fluids, soft condensed matter physics, phase transitions, the study of glass and amorphous solids, liquid crystals, self-assembly, surface-enhanced light scattering, and diffusion-limited aggregation. More recently, his laboratory has developed force spectrum microscopy, which is capable of measuring random intracellular forces. He has published over 700 papers, with more than 80,000 citations.

Weitz received his B.Sc. in Physics from the University of Waterloo in 1973 and his PhD in superconductivity from Harvard in 1978. He then worked as a research physicist at Exxon Research and Engineering for nearly 18 years, leading the Interfaces and Inhomogeneous Materials Group and Complex Fluids Area. He then became a Professor of Physics at the University of Pennsylvania in 1995, before moving to Harvard in 1999. He is currently member of National Academy of Sciences (US), National Academy of Engineering (US), and American Academy of Arts and Sciences.