Fundamentals on Bionanotechnologies - Bionanoelectronics: Bioinquiring and Bioinspired Devices - page 50

95 o C

77 o C

60 o C

the three zones with
constant temperature

input

output

Fig. 1.50 PCR lab on chip

of our topic. However, as we will see in the next chapter, micro- or nanofluidics
devices are integrated with nanoelectronic devices for biomolecule sensing. For the
interested readers, there are a lot of reviews and topics about microfluidics. We
mention here just a few of them. An early review on microfluidic integrated devices
is found in Erickson and Li ( 2004 ), while a brief review on droplets processing is
found in Tabeling ( 2009 ). Droplets microfluidics is reviewed by Teh et al. ( 2008 ),
while the biological applications of microfluidics is found in the topic of Tian and
Finehout ( 2008 ). The ultimate device of microfluidic is a lab-on-chip, which is
a device enabling the miniaturization, integration, and automation of biochemical
assays. There are many types of lab-on-chips, such as polymerase chain reaction
(PCR), which is used to replicate DNA and amplify it in a large amount.
This lab-on-chip, depicted in Fig. 1.50 , acts like a chemical amplifier and so is
the analogue of an electronic amplifier ( Kopp et al. 1998 ). PCR is based on three
steps: (1) heating the DNA solution at 95 ı C to separate dsDNA in single strands, (2)
heating at 50-65 ı C for primer binding to targeted sites (annealing), and (3) heating
at 72-77 ı C for primer extension with DNA polymerase, such as Taq. PCR is able
to produce 10 3 -10 6 copies of a DNA strand.
The fluid containing DNA is pumped into various temperature regions to
accomplish the PCR steps indicated in different gray colors in Fig. 1.50 ( Kopp
et al. 1998 ). The three temperature zones are preserved at constant values with the
help of thermostated copper blocks. Each cycle of melting doubles the number of
DNA molecules by changing the temperatures as indicated above.
The PCR lab-on-chip is formed by a single microchannel having a meandered
shape, which is hydrostatically pumped. The microchannel is etched in glass and
has a depth of 40 m and a width of 90 m. The output of the PCR is collected by
a capillary outlet.