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MicroPIV Systems

    • Standard MicroPIV
      The standard microPIV system is ideal for steady flow in complex microchannel geometries.
    • Time-Resolved MicroPIV
      Time-resolved methods are used for investigations of mixing or flow evolution.
    • Confocal MicroPIV
      When narrow depth of field is required, the confocal system is used to obtain a representative vector field from a thin slice.
    • Other MicroPIV Configurations
      Many different microPIV configurations are available for different types of measurements.

    MicroPIV systems - flow measurements in microfluidic devices and microchannels

    MicroPIV systems are PIV systems designed to for measuring flows in MEMS devices, microchannels, vessels and flow devices; with dimensions ranging from tens to hundreds of microns.  The typical arrangement for microPIV system is similar to PIV (using a camera and laser) but also uses a microscope for its magnification power to zoom into the micro-device for the flow field.  The figure illustrates some microchannel geometries and a typical vector field in a channel.

    Typical microchannels and a typical vector field in a channel

    Patented technique

    Pioneering work performed by Prof. Carl Meinhart at the University of California, Santa Barbara, Prof. Juan Santiago of Stanford University, Prof. Steve Wereley of Purdue University and Prof. Ron Adrian of Arizona State University led to a patented measurement approach that incorporated special optical system development, epifluorescence illumination, and ensemble processing algorithms.  With the exclusive right for the patent licensed by TSI, those methods were incorporated in the design of our microPIV systems to provide the most advanced and accurate tool for microflow measurements.

    Epifluorescence Illumination

    The epifluorescence illumination approach is key to our microPIV system. This design, in which the illumination and scattered light collection use the same optical access to the flow channel shown in the figure below, offers stable and easy access for the camera and maximizes image quality.  The fluorescent seed particles are excited by the 532 or 527 nm laser light but the image captured by the camera is from the emission signal of the fluorescent particles, using the filter cube assembly.

    Epifluorescence assembly for microPIV

    Ensemble Correlation

    The ensemble correlation processing algorithm provides results with the highest possible spatial resolution.  The technique computes the average of the correlation peaks from a number of images and then the vector field is calculated based on the final (averaged) correlation map.  Using this technique, the signal-to-noise ratio is significantly improved and gives very accurate velocity vectors.

    Laser Beam Delivery to Microscope

    Delivery of the laser light into the microscope for illumination is critical.  The laser light needs to be directed into the microscope precisely at an energy level sufficient enough to illuminate the flow model without causing any damage in the microscope.  A laser light guide or laser light arm can be used to couple the laser head with the lamp housing of the microscope.  When the parallel light beam comes out of the light guide, the beam goes through a neutral density filter and holographic diffuser.  The diffuser removes any hot spots in the laser beam to provide a uniform beam profile.

    Insight 4G for microPIV analysis

    The Insight 4G software includes many functions designed for microPIV analysis.  In addition to the ensemble correlation processing algorithm, the background subtraction helps remove particles that are out of focus due to volume illumination.  Subsequently, the analysis focuses on the particle within the depth of field, giving the representative vector field. The particle tracking scheme is part of the Insight software analysis and is ideal in boundary layer flow and near-wall measurement where particle density is typically small.

    Types of microPIV systems

    The different types of microPIV systems are configured from components to meet different requirements of flow measurements.  Major components of those systems are the camera, synchronization electronics, laser, microscope system and Insight 4G software.  The table below provides some details of the cameras, lasers, and microscopes typically used to configure the system.  It is important to note that the microscope system provided with the system is a COMPLETE functional microscope for two major reasons.  First, it can easily be expanded to accommodate other types of measurement (e.g. temperature measurement using PLIF technique with another camera).  Second, the microscope can be used on its own for other investigations, such as cell and biological measurements

     System Microscope System Cameras Lasers 
     Standard MicroPIV Nikon- or Olympus-based inverted or upright microscope Powerview series of high resolution cameras  Energy output up to 100 mJ at 15 Hz pulse rate 
     Time-Resolved MicroPIV  Nikon- or Olympus-based inverted or upright microscope  Model 630081 to 630087-based Phantom high-speed cameras  Energy output up to 30 mJ at 3000 Hz pulse rate
     Confocal MicroPIV  Nikon or Olympus inverted microscope with motorized Z-traverse Model 630081 to 630087-based Phantom high-speed cameras  CW laser with 100mW at 532 nm (part of the confocal optics)
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