Tuesday, 03/16/2004
4:00 PM
Steinman Hall, Room #312
(Chemical Engineering Conference Room)

Professor Sascha Hilgenfeldt
University of Twente
Department of Applied Physics and Institute for Biomedical Technology

"Bubble-Powered Streaming Flow: From Membrane Mechanics to MEMS "


In biophysical or lab-on-a-chip applications, it is often desired to transport cells or lipid vesicles in suspension, or to porate the cell membrane in order to transfect drugs and DNA. Two features are required to accomplish these tasks: efficient microfluidic transport and strong forces localized on the microscale. We show that both demands are met employing microbubbles as actuators for microfluidic flow. Oscillating microbubbles, excited by an ultrasonic wave, give rise to a steady streaming flow due to the inherent nonlinearities of fluid dynamics. The streaming is very intense close to a bubble, inducing strong localized shear forces sufficient to deform, porate and rupture lipid membranes. We have observed these processes experimentally and described them quantitatively using Stokes singularity theory. Combining bubbles with passive flow elements such as solid particles, we achieve directional control over the streaming flow on larger scales and demonstrate that bubble streaming can be used for efficient transport of microparticles in arbitrary directions. A multitude of microbubble-based MEMS applications in cytometry and membrane mechanics becomes feasible.

  • Bachelor's degree in physics, 1991.
  • Bachelor's degree in mathematics, U. Munich, 1995.
  • PhD, U. Marburg, physics, 1997.
  • Postdoctoral researcher, Dept. Theoretical Physics, U. Marburg,1997/98.
  • Postdoctoral fellow with Howard Stone, Harvard, 1998-2000
  • Assistant Professor, Dept. Applied Physics and Institute for Biomedical technology, U. twente, Netherlands, since 2000.
  • Visiting Scholar, U. Chicago, since 2001.