Tiny channels designed to control the flow
of minuscule amounts of fluids are a major component of Labs-on-a-chip,
which promise to enable inexpensive, hand-held devices for chemical and
Researchers from Cornell University have devised a simple, inexpensive
way to construct fluidic channels whose corners are elliptical rather
than sharp, which permits fluid to flow more freely.
To make the channels, the researchers used a spinning technique
to deposit parallel, evenly-spaced polymer fibers onto the surface of
a silicon, silicon dioxide or glass chip. They then added a layer of liquid
glass, a chemical that hardens to a transparent substance when heated.
The fibers are as small as 100 nanometers in diameter, or one-tenth the
girth of an E. coli bacterium.
The researchers used photolithography -- a process that uses chemicals
and light to pattern materials -- to add reservoirs to the chip, then
etched holes at each end using a hot beam of plasma. The more tedious
work -- making many tiny channels -- was done simply by heating the surface
to 350 degrees Celsius to decompose the fibers, leaving channels with
The channels could be used to separate, count and analyze biological
molecules like DNA, according to the researchers.
The channels could see limited use in commercial devices in two
to five years, and more widespread use in five to ten years, according
to the researchers. The work appeared in the December 8, 2003 issue of
Applied Physics Letters.
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