Page 277 - Organic Electronics in Sensors and Biotechnology

254 Cha pte r S i x

field aims to transform the analytical sciences, using techniques devel-
oped in the silicon processing industry, to engineer miniature devices
on which chemical and biological processing can take place under pre-
cisely controlled conditions. Miniaturization of chemical processing
provides significant advantages over conventional systems. These
include (1) reduced analysis times, (2) cost reductions through down-
scaled fabrication and reduced consumption of reagents, (3) superior
control of reaction conditions, (4) enhanced ability to carry out parallel
processing, and (5) the ability to perform in-the-field or point-of-care
measurements. Typical microfluidic devices are fabricated by forming
continuous channels in silicon, glass, or plastic substrates and then
sealing the channels using a second substrate as a lid (Fig. 6.32). All the
standard chemical processing steps can be carried out in microfluidic
devices, e.g., filtering, mixing, heating, cooling, separation.
The workhorse of clinical diagnostics is the immunoassay. In
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simple terms, an immunoassay is a biochemical test that quantita-
tively measures the presence of a specific analyte in a biological fluid
(usually serum, urine, or saliva) using the specific reaction of an anti-
body to its antigen. The final signal is usually optical, e.g., a qualita-
tive color change or a quantitative absorption or emission signal.

FIGURE 6.32 Typical microfl uidic devices. (Picture courtesy of Wikipedia.)