KðÞ¼ωε*pε*mε*pþ 2 ε*m; ε*
p
ðÞi¼p, m
¼εijσ 1
ε 0 ω
ð 2 : 7 ÞWhere, p and m refer to the particle and medium,ε is permittivity,σ is
conductivity andωis the angular frequency of applied field (ω¼ 2 πf). Dielectro-
phoresis can be carried out in various circumstances, i.e., using metal electrodes,
liquid electrodes, carbon electrode, insulator based DEP and light induced DEP.
The detailed classification of the DEP techniques is given in Fig.2.28.
As Fig.2.28 represents, DEP can be performed using various types of electrodes,
even electrodeless DEP is possible using techniques. Initially metal electrode DEP
were used in which metal electrodes used to be printed on the substrate surface.
Printed electrodes further possess various characteristics and various designs of
electrodes (interdigitated electrodes (IDEs), other discrete shapes etc.) It has
advantage of performing the process at low voltage value as the electrodes are
placed very near to each other. Very low volume of solution (volume corresponding
to 30 μm height from the base) can effectively undergo DEP process. Beyond this
height, the efficiency reduces steeply. In metal electrode category, 2D and 3D types
of electrodes are there. 2D electrodes are also called as the planar electrodes. To
increase the volume respective to further height, 3D metal electrodes (Extruded
metal electrodes, thick layer of doped silicon electrodes) were evolved. With time,
several limitations of the metal electrode DEP like constraint on the volume that
can undergo DEP and erosion of metal electrodes with time has led to evolution of
Fig. 2.28 Classification of DEP techniques
66 G. Bhatt et al.