Biomedical Engineering Reference
In-Depth Information
4.
EXPERIMENTAL MEASUREMENTS OF ELECTROKINETICS
Two examples of using electrokinetics to manipulate small particles will be
presented here. Since both examples employ the
PIV technique to quantify the
response of small particles to the electrically induced forces, a brief introduction
to the technique will also be given. The first example, electrokinetic flow, illus-
trates the electrothermal effect and the second illustrates the dielectrophoretic
effect.
4.1. Microparticle Image Velocimetry (
PIV)
PIV is a technique that has been developed recently to measure the veloc-
ity of small scale flows in a spatially resolved manner (19). Figure 9 shows the
typical layout of a
PIV system. The flow is illuminated by either a broad-
wavelength continuous light source, such as a mercury vapor lamp, or a pulsed
laser, such as a frequency-doubled Nd:YAG. Normally,
PIV is used to measure
the velocity of small-scale flows by measuring the motion of small tracer parti-
cles either naturally present in the flow or artificially added to the flow. In the
following examples, however, the motion of the fluid is not the primary subject
of study, but rather the motion of the suspended particles in response to an elec-
trically applied force. Regardless of whether the fluid motion or particle motion
Figure 9
. Diagram of typical
PIV system.
