AAWSAP DIRD, Biosensors and BioMEMS: A Survey of the Present Field, March 2010

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move through the channels where processes of separation, filtering, mixing, heating,
reaction, and waste disposal can occur in a programmed sequence. Color changes after
a sequence of chemical steps might be used to indicate the presence and concentration
of an analyte. Optical absorbance or transparency can be read by a simple light
emitting diode (LED) and photodetector system that measures light passing through the
glass sample cell.
LAB CHIPS
A class of microfluidic devices known as lab-chips or Lab-on-a-Chip (LOC) have made
their appearance in the market place. These devices are miniature chemical analysis
systems that replace many of the manual and laborious steps associated with analytical
chemistry. They are generally produced by MEMS techniques and often, but not always,
incorporate electrical systems on the devices.
Automated MEMS-based lab-on-a-chip platforms have become an established system
for basic life science research and drug discovery. They are used to assess the
characteristics of isolated DNA or proteins.
One of the most useful products of bioMEMS instrumentation is the ability to manipulate
small quantities of DNA using microfluidic pathways to perform chemistry with only the
content from a single cell. BioMEMs enable new techniques in genomics (the study of
sets of genes, gene products, and their interactions) and proteomics (the study of
proteins, the expression of genes in health and disease).
These systems are being made now by companies including Affymetix, Caliper,
Nanogen, and Agilent for processing samples on a microfluidic chip for separation and
detection. Figure 31 shows the variety of such systems currently on the market.
Such devices can replace a number of gel electrophoresis operations and substantially
improve work flow sample handling and analysis, lower per sample analysis by 10X and
minimize sample and reagent use.
The physics of these microfluidic systems enable some unique features, including
smooth laminar flow through the microchannels, high surface area to volume ratios,
small thermal mass, and strong effects by electric fields. Microfluidic devices also lend
themselves to enhancements for single cell detection, fluorescence detection, sorting
schemes, and unique fluid separation methods.
The advantages of lab-on-chip devices include:
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Improved fluid transport by electrokinetic effects and miniaturized pumps.
•
Efficient molecular and particle separation and immobilization.
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Smaller sample requirements and carrier volumes.
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Reduced reagent consumption and expense.
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Integration of channels, mixers, separators, reaction chambers, electrodes, and
detectors into single devices.
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