Microfluidics for Biologists Fundamentals and Applications

for the thermocouple. In this research the optimal placement test run for placement
of RTD is performed. The configuration chosen for RTD placement is heater is
placed at the bottom side of the chip while RTD is placed on the upper side of the
chip. RTD is used in four wire measurement mode which minimizes measurement
errors due to lead resistance. Various placement methods for RTD are studied to
obtain a linear relation in input and output parameters. Parametric identification
using Auto Regressive with Exogenous Inputs (ARX) method is performed and 2nd

2.1

1.8

1.5

1.2

0.9

0 50 100 150 200 250 300

Time in Minute Time in Minute

2.0

1.5

1.0

0 50 100 150 200

Relative Fluoroscence Increase Relative Fluoroscence Increase

ab

Fig. 2.32 (a) Plot showing the trend in increase in fluorescence intensity during DEP of different
bacterial cell (normal) concentrations with respect to time, :10^2 cfu/mL; :10^3 cfu/mL; :10^4
cfu/mL; :10^6 cfu/mL; :10^7 cfu/mL; :10^9 cfu/mL; : control, (b) Plot showing the trend in
increase in fluorescence intensity during DEP of different bacterial cell (conjugated) concentra-
tions with respect to time, : 109 cfu/mL; :106 cfu/mL; :104 cfu/mL; : 103 cfu/mL; :
control (Reproduced from Nayak et al. [ 98 ] with permission from the Nature Publishing Group)

Fluid only

(Very less cells)

Diversion

Outlet

Fluid and cells

(Small flow rate)

Main

Outlet

Main

Inlet

DEP based

Diversion Electrodes

Fluid Only

(Large flow.no cells)

Fig. 2.33Principle of operation of the dielectrophoresis-based diversion and diversion of cells
(Reproduced from Bhattacharya et al. [ 99 ] with permission from the Royal Society of Chemistry)

2 Microfluidics Overview 71