Characterization of fluid transport in microscale structures
A new tool for imaging both scalar transport and velocity fields in liquid flows through microscale structures is described. The technique employs an ultraviolet laser pulse to write a pattern into the flow by uncaging a fluorescent dye. This is followed, at selected time delays, by flood illumination with a pulse of visible light which excites the uncaged dye. The resulting fluorescence image collected onto a sensitive CCD camera. The instrument is designed as an oil immersion microscope to minimize the beam steering effects. The caged fluorescent dye is seeded in trace quantities throughout the active fluid, thus images with high contrast and minimal distortion due to any molecular diffusion history can be obtained at any point within the microchannel by selectivity activating the dye in the immediate region of interest. The author reports images of pressure- and electrokinetically-driven steady flow within round cross section capillaries having micron scale inner diameters. The author also demonstrates the ability to recover the velocity profile from a time sequence of these scalar images by direct inversion of the conserved scalar advection-convection equation.
- Research Organization:
- Sandia Labs., Livermore, CA (United States)
- Sponsoring Organization:
- USDOE Office of Energy Research, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 588570
- Report Number(s):
- SAND--98-8227; ON: DE98052595
- Country of Publication:
- United States
- Language:
- English
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