|Optoelectric Micro/Nano Particle Manipulation |
Mechanical and Aerospace Engineering
|Steve Wereley, Purdue University|
3:30 PM, Eng. Room B120
Recently our research group has developed an innovative method for capturing, concentrating, manipulating and sorting populations of particles ranging from single particles to thousands of particles (Lab-on-a-Chip, 2008; Microfluidics and Nanofluidics, 2008). This novel technique uses a simple parallel plate electrode configuration. Transparent electrodes comprised of Indium Tin Oxide (ITO) on glass substrates were used to generate an electric field in the fluid but also to allow light into and out of the fluid. Near-IR optical illumination causes subtle localized heating, creating an electric permittivity gradient, that in turn drives a microscopic toroidal vortex. The vortex efficiently transports particles to a preferred location, usually the surface of the electrode. The flow velocity is characterized as a function of the AC signal frequency and the strength of electric field using conventional microscopic imaging along with micro particle image velocimetry (mPIV). mPIV measures the velocity of a flow by tracking the motion of sub-micron tracer particles carried by the flow. To measure high velocity, small length scale flows, high speed lasers and interline transfer CCDs are used in conjunction with a microscope to image the tracer particles with sub-microsecond temporal resolution. The application of this technique to several typical micro systems, including the optoelectric vortex described earlier, will be presented and the results discussed. Recent trends in mPIV have allowed the spatial resolution of the technique to be increased such that even sub-micron domains can be measured in a spatially resolved manner.