| Flows
in micro-fluidic channels have been investigated for possible applications in
Micro-Electro-Mechanical-Systems (MEMS) devices. Both pressure and electro-kinetic
driven flow have been analyzed. We have used high aspect ratio rectangular channels
to analyze the flow where the channel height was varied between 1 to 20 microns,
and the channel width was kept between 50 to 300 microns. Soft lithography techniques,
which offer rapid prototyping, easy multilayer fabrication, mass production capability
and biocompatibility, was utilized to fabricate various parts of the micro-fluidic
chip, such as channels, connectors and reservoirs. Poly-di-Methyl-Siloxane (PDMS),
a polymeric based material, which is transparent to ultraviolet and visible light,
is used as the channel material. PDMS material consists of a base elastomer (vinyl
group and platinum catalyst) and a curing agent (cross linker Si-H), and it spontaneously
creates negative charges on the surface when it comes in contact with polar media,
such as de-ionized (DI) water. Our experimentations include unsteady and steady
flow measurement in the micro-channels under the action of electric and pressure
field. Experimental results show that for pressure driven flow, the flow velocity
increases with the applied pressure. On the other hand, for electroosmotically
driven flow, the flow velocity depends on the concentration and the electric field. |
