Electrical wiring diagrams, whose conductive tracks are
thinner than 20 micrometers and thus invisible to the naked eye, can
now be produced using new BayInk® nanoparticulate silver inks.
The aqueous nano dispersions were developed by Bayer
MaterialScience AG in cooperation with Bayer Technology
Services. They are about to be released for commercial sale and are
tailor-made for a new generation of ink jet printers that can be used
to produce wiring diagrams cost effectively with a high level of
productivity - even on an industrial scale. "Our nano inks achieve ten
percent of the specific conductivity of elemental silver with only a
relatively low percentage of silver by weight. At the same time, they
adhere very well to a wide variety of substrates, such as
polycarbonate, polyethylene terephthalate, thermoplastic polyurethane
and glass," explains Dr. Stefan Bahnmüller, nanotechnology
expert in the New Technologies group at Bayer MaterialScience.
The curing temperatures of the new nano inks are well below
130 °C - much lower than those of most commercially available
silver inks. Therefore, BayInk® can be printed on a variety of
plastics that would otherwise not be able to withstand the thermal load
during the curing process. In addition, the printed conductive tracks
are very flexible and extensible. "This is, for example, particularly
important for plastic films that are shaped using the film insert
molding process after the wiring diagram has been printed, and are then
back-injected," says Bahnmüller.
Printing wiring diagrams using an ink jet printer is an
attractive option because the process is very straightforward and
precise. What’s more, unlike chemical etching processes, it
is also ecologically safe. In the past, silver inks in ink jet printers
often caused problems when used on an industrial scale because the
printers’ spray nozzles would clog easily, causing high
reject rates and uneconomical production. "In contrast, the size and
distribution of the particulates in our nano inks are perfectly matched
to the process, which means that the nozzles don’t clog, thus
enabling continuous high-quality production without interruption,"
Bahnmüller envisages great potential for
BayInk® - which incidentally can also be used in screen
printing - in the field of printed electronics, for instance with
sensors, actuators and radio frequency identification systems (RFID).
Conductive tracks of photovoltaic cells could also be produced using
nano silver inks. In the automotive industry, wiring diagrams produced
using BayInk® are ideal as an alternative to cable harnesses,
for example in instrument panels. Very thin filaments based on nano
inks, which are invisible to the naked eye, could be used in rear
windows or headlamp lenses to prevent them from steaming up or icing
At present, Bayer MaterialScience is working with the
Universities of Jena and Marburg to reduce the width of conductive
tracks made of BayInk® still further.