Imaging and Manipulation of Biomolecules - Bionanoelectronics: Bioinquiring and Bioinspired Devices - page 120

Fig. 3.8 The PIRE electrode

cell flow

in

ITO

out

6x6 array

Fig. 3.9 Electrodeless DEP

DNA in pH = 7 solution

of DNA

E lines

etched quartz

Nanogaps studied in the previous chapters can be used also for DEP. For example,
20-nm gold nanoparticles were manipulated using positive DEP in a nanogap with a
width not exceeding 100 nm ( Kumar et al. 2009 ). The applied signal in this case
had a frequency of 1 MHz and an amplitude of 3 V. In this way, assembles of
nanoparticles can be generated. Moreover, a lab-on-chip can be created using DEP
to separate cells with the help of a pair of embedded electrodes and an insulator
hurdle. In this situation, the amplitude was 10 V and the frequency had a value of
200 kHz ( Kang et al. 2009 ).
But not only planar metallic electrodes can be used for DEP but also dielectric
constrictions ( Chou et al. 2002 ). For instance, a 1-m gap between two etched
quartz substrates, as shown in Fig. 3.9 , can be used to DEP ssDNA and dsDNA
molecules and to analyze their physical properties at low frequencies, of 200-
1,000 Hz, when the peak-to-peak amplitude is 1 kV. In the geometry in Fig. 3.9 ,
the force takes a maximum value not at the center of the gap but where the product
between the electric field and its gradient is maximum.
Carbon nanotubes were used also as DEP electrodes with the aim of trapping
short DNA molecules ( Tuukkanen et al. 2006 ). The DEP was used as well to trap
and determine the dielectric permittivity of isomated DNA. Experimental data show