Biomedical Engineering Reference
In-Depth Information
functions), and where resources are low (e.g., in developing countries). They help
deliver appropriate and prompt treatments and improve clinical outcomes [ 5 - 7 ].
The development of microdevice-based diagnostics originated from driving
forces in molecular analysis, biodefence, molecular biology, and microelectronics,
the last of which provided tools for miniaturization and microfabrication [ 1 , 8 ]. How-
ever, miniaturized silicon-based devices were not suited to biological applications
with physiological fluids because of difficulty of optical detection, high material
cost, low biocompatibility, and lack of available rapid prototyping. The extension of
microfabrication techniques to first glass then polymers such as elastomers and hard
plastics enabled the construction of a set of microfluidic mechanical devices grouped
under the broad category of microelectromechanical systems (MEMS) or lab-on-a-
chip (LOC) systems [ 9 ]. These technologies, in turn, have led to developments in
sensors for medical, environmental, and life science applications [ 1 ].
1.2
Comparisons Between Point-of-Care Tests in Developed
Versus Developing Worlds
Integration, portability, low power consumption, automation, and ruggedness are
several important qualities common to point-of-care tests in both developed and
developing countries. (Here we define the developed world as the group of high-
income countries and the developing world as the groups of low- and middle-income
countries, based on classifications by the World Bank). These general design con-
straints suggest some LOC components and procedures to be more appropriate than
others in point-of-care settings (Fig. 1.1 ). In general, the differences in appropriate
LOC procedures are more pronounced between tests performed at centralized
settings versus point-of-care settings than between point-of-care tests performed at
high-income versus low-income settings [ 10 ]. For instance, the presence of reliable
ground electricity at centralized testing facilities allows for active mixing on-chip
and bulky signal detection systems which draw significant power. At point-of-care,
however, the lack of ground electricity requires passive or low-power approaches for
mixing on-chip and portable signal detection systems which can be powered by bat-
tery (or read by eye) (Fig. 1.1 ). By virtue of the common design criteria in point-of-
care tests, engineers interested in developing microdevices for point-of-care testing
in resource-limited settings can leverage the large body of existing research on LOC
designs for point-of-care testing for physicians and home use [ 11 , 12 ], devices for
military applications [ 13 ] and first responders, and extraterrestrial sensors [ 14 - 16 ].
There are, however, at least two important distinctions between LOC point-of-
care tests intended for developed countries versus developing countries. The first
is cost. Due to vastly smaller budgets via public financing, the budget available to
spend on medical diagnostics devices in developing countries is limited compared
to that of developed countries. Thus, the cost of the microfluidic device (which
includes both the material and the manufacturing process) must be kept extremely
low in POC testing in developing countries; the fixed instrument must be portable
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