Microfluidics for Biologists Fundamentals and Applications

parallel and in a relatively short period. In one run the researchers were able to run
20 different samples (glucose and BSA) within 7.5 min (another 10.5 min for the
color to fully develop). Thus, an 18 min assay is enough for measuring two analytes
in 20 different samples (Fig. 8.8A)[ 71 ]. In another work Bercovici
et al. demonstrated an experimental and analytical study of a novel paper-based
analytical device for sample focusing using isotachophoresis (ITP) [ 72 ]. The
authors used 2.5 mm wide channels and described the processing of a 30μL sample
in several minutes. It was observed that the dispersion was much significant in the
paper as compared to glass, and the peak enhancement on the order of 1000-fold in
several minute by substantial sample focusing (Fig.8.8B). Thus, obtaining high
sample concentrations in paper results in enhanced reaction kinetics and creating
low-cost devices with much-enhanced sensitivity. Further, this paper-based ITP can
process large sample volumes, but the small dimension of the microchannels limits
their application to the analysis or processing of small sample volumes. The
realization of ITP in larger channels or larger diameter capillaries is challenging
due to hydrodynamic instabilities and excessive Joule heating. Therefore, these
papers based ITP can be helpful in detection of extremely dilute samples
(e.g. detection of bacteria at 10–100 copies per mL). In the next section we will
discuss the potential application of PoC devices for molecular diagnosis and
immunodiagnostics.

Sample input (Raw samples)

Pretreatment of sample

(fluid handling, derivatization, lysis of cells, concentration, extraction,

and amplification)

Sample separation (electrophoresis, liquid chromatography, molecular

exclusion, field-flow fractionation)

Amplification or post treatment

Detection (fluorescence, UV/Vis absorption, amperometric,

conductivity, Raman, electrochemical)

Fig. 8.7 Scheme showing different steps involved in a general procedure for operation of a MF
diagnostic device

8 Biological Applications of Microfluidics System 209