oil phase. In optical and electrical sorting of cells, high-frequency electrical fields
create forces which move cells into potential wells specified by the placement of the
electrodes or the use of light patterns that change the conductivity of a conducting
surface. Similarly, the electrical forces can be used in dielectrophoresis to direct the
cell to a particular location. After single cell sorting, the analysis of cell components
can be done using cell analysis techniques.
Single cell analysis (SCA) reduces the biological noise, and it provides funda-
mental improvements in experimental design and data analysis for applications
predicated on single cells. Stem cells, for example, hold great potential for regen-
erative medicine as they are capable of self-renew and can divide along different
lineages. However, the other cells like the embryonic stem cells, adult stem cells,
and induced pluripotent stem cells are all heterogeneous populations. SCA can
target specific populations and, therefore, elucidate signaling pathways and net-
works for self-renewal and for differentiation [ 66 ].
3 Microfluidics in Diagnostics
Biomedical diagnostics has been an important application area of MF technologies.
The unique features of MF technology make it naturally suitable for the fabrication
of PoC testing devices. Till date, some prior DNA separation techniques and
diagnostics have been successfully miniaturized [ 67 , 68 ]. MF seeks to overcome
the difficulties or challenges in traditional assays in medical diagnoses such as cell-
based assays, disease screens and drug screens. Many MF systems are integrated
with sensing modules or sample-pre-treatment modules, which increases the effi-
ciency of the assays and reduces cross-contamination. These advantages have
potentially lowered the cost of the assays as well as provided a faster diagnosis.
Integration of multiple components/functionalities (sample preparation, detection,
data processing) on a simple to use single device has enabled their use by
non-specialized person. Moreover, the parallel analysis allows multiple tests to be
run simultaneously, either in the same sample or multiple samples. A variety of
samples including blood, urine, saliva, stool, and plasma, amniotic and cerebral
fluids have been used for diagnosis in PoC devices [ 69 ]. Figure8.7demonstrates
different steps of a general analytical procedure involved in a MF diagnostics
device.
Various materials like glass, silicon, and polymers have been used for the
fabrication of various MF devices, but recently, the application of paper in MF
device development is emerging as a promising format for PoC devices. MF paper-
based analytical devices orμPADs as coined by Whitesides are thin, small, cheap,
flexible and can easily be disposed of thus, making it an ideal platform for
healthcare applications [ 70 ]. The PoC devices are designed to detect specific bio-
molecules like DNA, RNA, whole cell or biomarkers, etc. specific to a particular
disease. The paper-based assay is suitable for measuring multiple samples in
208 S. Solanki and C.M. Pandey