Woodruff School of Mechanical Engineering

Faculty Candidate Seminar


Visualization and Manipulation of Swimmers and Fluids at Microscopic Scale


Dr. Bian Qian


Massachusetts Institute of Technology


Thursday, January 31, 2013 at 11:00:00 AM


MRDC Building, Room 4211


David Hu


In this talk, I will present our recent work on manipulation of microswimmers and experimental research on electrorheological fluids in small-scale hydraulics. Manipulation of microswimmers by adaptive photon nudging - The capacity to navigate microscopic swimmers in complex liquid environment could have wide-ranging implications in the fields of nanorobotics, microbiotechnology, microfluidics and directed assembly. In the first part of the talk, we will present a simple scheme for remotely maneuvering individual microscopic swimmers. The proposed strategy utilizes rotational random walks to reorient the micro-swimmer and turns on propulsion only when the swimmer is aligned with the target location. The strategy is illustrated in a principle-of-proof experiment steering a gold-coated Janus micro-sphere using adaptive laser heating. Beyond experimental demonstration, computer simulation is performed to examine the strategy and identify the key dimensionless control parameters. Structure and dynamics of electrorhelogical fluids in a microchannel - Electrorheological (ER) fluids, which have tunable viscosity under the influence of external electric field, have been used in a variety of hydraulic components, including clutches and valves. Recent advances in design and fabrication of microscale ER valves offer new opportunities for fluid control at microscale. Aiming at better design of fast-actuated ER valves, we experimentally investigate the dynamic response of electrorheological fluid flows in a rectilinear microchannel, an idealized model of ER valves. Using high-speed microscopic imaging, the evolution of particle aggregates in ER fluids subjected to temporally stepwise electric fields is visualized. In the second part of the talk, we will present experimental measurements of the evolution of particle structures and discuss its correlation to field strength and flow rate. In addition, a phenomenological model is developed to quantitatively describe and predict the evolution of microscale structures.


Dr. Bian Qian is a postdoctoral research associate in Mechanical Engineering at Massachusetts Institute of Technology. His research interests involve the study of micro-scale fluid mechanics as applied to micromanipulation, microtechnoloy and small-scale robots, with a recent focus on field-activated fluids in small-scale hydraulics. Dr. Qian received his MS and PhD degrees in Applied Mathematics and Engineering from Brown University in 2009 and 2010 respectively. His research has been featured on the Discovery Channel's series Weird Connections program and reported by New Scientist and Chemistry World.


Refreshments will be served.