1.1 Biosensors-Involvement of Microfluidics
According to a recent National Institute of Health (NIH) report, point-of-care
(POC) testing has the potential to introduce a paradigm shift into personalized
medicine by creating a link between disease diagnoses and the ability to tailor
therapeutics to the individual [ 1 ]. POC testing promotes a shift away from tradi-
tional diagnostic tests in the clinical laboratory setting to near-patient settings,
providing physicians with timely diagnostic details to make appropriate decisions
regarding diagnosis and treatment. The global POC market for in-vitro diagnostics
is poised to grow at a CAGR of 9.3 % from 2013 to 2018 and is said to reach $27.5
billion by 2018 [ 2 ]. Examples of POC testing have become a familiar topic within
the research community in recent years. Successful examples of these widely
adopted POC systems are the glucometer, used for managing diabetes mellitus
and the disposable lateral flow immuno-strip, used for pregnancy testing. To qualify
as a successful candidate for POC diagnostics, the sensitivity, specificity, portabil-
ity, and cost of the biosensor system must be better than that of centralized
laboratory assays [ 3 , 4 ]. In order to achieve these requirements, most of the POC
sensors are built around the idea that they should operate as lab-on-chip (LOC)
devices; implying that they are miniaturized automated laboratories. The only way
to achieve this device goal and out-compete the need for cumbersome lab tech-
niques that require culture bottles, petri dishes, and microtiter plates is to employ
microfluidics. Analysis rates for POC devices integrated with microfluidic channels
are usually shorter and several assays can be integrated in a single system without
extending the size and complexity of the device. In addition to this, several steps of
the analytical procedure can be integrated and automated within the system. An
idealized concept of a POC device [ 5 ] is shown in Fig.6.1.
Based on George Whitesides’definition [ 6 ], microfluidics is “the science and
technology of systems that process or manipulate a small volume of fluids, typically
(10^9 –10^18 L), using channels with dimensions of tens to hundreds of microme-
ters”. The high surface-area-to-volume ratio of microfluidic devices leads to
enhanced heat and mass transfer. In addition to the latter, interfacial phenomena
that are not usually observable at the macroscale, such as the domination of surface
forces instead of inertial and body forces can be elucidated. While microfluidics
hold great promise in POC medical diagnostics, limitations to its applicability still
exist. Fabrication costs and material compatibility are two major concerns in
material development; novel materials and processes that overcome these limita-
tions are addressed in this chapter.
146 P. Manickam et al.