Carbon nanotubes (CNTs) are tubular cylinders of carbon atoms that possess incredible mechanical, electrical, thermal, and chemical
properties. In fact, the structures are 200 times
stronger than steel and experience very little physical
corrosion typical of other metals.
in three main
forms and are
how many walls
of carbon exist
tube. A single-
wall CNT has
a single tube; a
10 to 20 walls
each other; and
a few-wall CNT has two or three walls.
Multi-wall CNTs are easier to produce than single-wall CNTs, while few-wall CNTs are still a relatively
new category. South West Nano Technologies (SWeNT)
distinguishes itself as one of the only companies that
produces all three types at a commercial scale. Recently,
the company demonstrated the use of carbon nanotube
inks as a material for specific touch capacitance and
membrane switch replacement applications.
Last November, SWeNT had the opportunity to
showcase the technologies at the Printed Electronics
USA Show in Santa Clara, CA. The company exhibited
a transparent conductive ink material, which is
commercially available, and a semi-conducting ink
material, which is currently in the R&D stage. The
former is used for touch sensor applications, transparent
electrodes for display products, and for smart windows.
The latter is typically used for printing transistors and
various types of sensors.
What makes the company’s transparent conductive inks
unique is that they’re printable. Manufacturers must
usually etch away at a transparent conductive film to
form patterned circuits, but by using this approach,
manufacturers can print the transparent conductive ink
exactly where it is desired on the circuit. “There is no
waste of material,” explains Dave Arthur, SWeNT CEO.
“You don’t have the associated cost with etching away
the material and dealing with waste.”
SWeNT’s design philosophy has been to formulate
the inks so they are printable with standard industrial
printing equipment. For example, the company has
developed a screen-printing ink that can be printed on
any screen-printing press and a slot die coating ink that
can be coated in any slot die coater.
Aside from the transparent conductive ink’s printability,
the ink is also stretchable. “This capability of nanotubes
to stretch and still maintain their electrical properties
is very exciting from a design standpoint,” says Arthur.
“It’s consistent with wearable electronics, flexible
electronics, and 3D-formed electronics.”
The ability to form a three-dimensional shape after
it’s been printed would allow touchscreens to have
curved touch buttons. For instance, a 3D button on a
car’s display screen could guide a driver’s finger where to
touch. Taking one’s eyes off the road would no longer be
When first put on a screen,
inks must have a consistency
like paste so they don’t
drip through. Then when
the squeegee passes over
the ink to force it through
the screen, it must become
thinner to flow. After it
flows through the screen
and the ink is printed onto
the surface of the desired
substrate, the ink must stop
immediately so it doesn’t
lose precision of the image
that was just printed.
“Essentially, you need a
material that is a paste, and
Transparent, conductive inks to transform touch capacitive devices.
Kaylie Duffy, Associate Editor, PDD
Thermoformed Buttons using SWeNT
Carbon Nanotube Ink. (Photos courtesy of
South West Nano Technologies)
South West Nano Technologies
demonstrating 3D capacitive
touch sensor using
carbon nanotube ink at PE