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Electrophoretically Deposited Polymers for Organic Electronics 387

is passed through, which seriously affects the efficiency of the process
and the uniformity of the deposit. Electrolysis of water occurs at low
voltages, and gas evolution at the electrodes is inevitable at field
strengths high enough to give reasonably short deposit times. This
causes bubbles to be trapped within the deposit, unless special proce-
dures are adopted, and damage the film topology. Another electroki-
netic phenomenon occurring in an aqueous EPD is water electroos-
mosis, which consists of the movement of the liquid phase because of
an external electric field. This could be helpful in EPD because it
would accelerate drying of the deposit surface which is in contact
with the electrode. So if the process is well controlled, demolding of
the self-supported deposits can be easier. Contrarily, if the deposits
were too thick, or the process was too fast, crack formation would
occur as a consequence of the drying gradient.

10.4 Scope of Electrophoretically Deposited Polymers
It has been shown that EPD has gained considerable interest in recent
years for fabrication of advanced materials. The process is simple,
easy to use, and cost-effective, and it has found innumerable applica-
tions including thin- and thick-film deposition, layered ceramics,
hybrid materials, fiber-reinforced composites as well as nanocompos-
ites, nanoscale assembly of two- and three-dimensional ordered
structures and micropatterned thin films. However, the process needs
judicious choice of solvent media such that an appreciable magnitude
of surface charge is developed on the powder surface in the suspen-
sion to ensure stability of the suspension as well as facilitate high
electrophoretic mobility. EPD has a number of advantages over the
usual filtration methods, including rapid but controlled deposition
over a wide range of substrate materials. As long as the substrate is
conducting, an adherent coating can be obtained. The EPD technique
is a widely used industrial process that has been applied successfully
for deposition of, e.g., phosphor for displays. It is an automated and
high-throughput process that in general produces films with good
homogeneity and packing density.
The EPD process is found to be the most promising technique for
homogeneous, smooth, and rigid deposition of CNT with controlled
thickness and morphology. In addition, the technique can be readily
extended to allow the coating of CNTs onto large planar substrates,
wires, individual fibers, fibrous structures, and porous components.
These CNT-based films have numerous applications for these net-
works: antielectrostatic coatings; electrochromic or electrically heated
windshields; field emitters; energy applications; displays; electro-
magnetic screening and touch panels; transistors for logic elements in
macroelectronic systems or for optical elements with highly anisotro-
pic properties; sensors; optoelectronics; and diodes. Moreover, elec-
trophoretically deposited CNT films are robust and provide new