Getting started with printing circuits is a relatively
simple and inexpensive process. There are three main things you will need; an
inkjet printer, conductive ink, and a substrate.
When selecting a printer, almost any inkjet printer will
work. Some researchers claim that it is best to use a piezo-driven printer
rather than a thermal-driven one as it is less likely to alter the structure
and properties of the conductive ink.[1] It doesn’t need to have fancy
touchscreen controls or wireless connectivity. Just look for a cheap printer
that you would feel comfortable taking apart and modifying. Studies have shown
that Brother Co. printers are the preferred option when it comes to printing circuits
due to their nozzles releasing higher volumes of ink. [2] More ink on the page means
that there is a better chance of a solid connection or trace being made. The
projects on this blog will use a Brother MFC-J450DW. This model was chosen mostly
due to the fact that it was the cheapest on Amazon for about $80 at the time of
writing. It is also recommended that you purchase empty refillable ink
cartridges that are compatible with your model of printer. Trying to reuse the
standard ink cartridges may end up contaminating your conductive ink and lead
to poor connections. These refillable cartridges can range anywhere from $5-20
depending on the model of printer they are for.
Next you will need the ink. There are many properties such
as viscosity, surface tension, volatility, and particle size that need to be
taken into consideration for choosing a suitable ink. Luckily, an extensive
amount of research has already been done on this and there is a clear winner.
Silver nanoparticle ink, part number NBSIJ-MU01, from Mitsubishi Paper Mill
works the best for most applications.[3] This ink can be purchased
from Diamond-Jet for $340.00 per 100 ml.[4] Admittedly, this does sound
like a daunting price at first. However, most conventional ink cartridges only
contain between 10 – 15 ml of ink inside of them. So overall the price per ml
isn’t that much more expensive. With a 100 ml of silver nanoparticle ink you will
be able to print hundreds of circuits.
Another benefit of the NBSIJ-MU01 ink which helps justify
the price is that it is chemically sintered. Sintering is the process which
take a powdered material or solution and transform it into a solid. With inkjet
printing the printer does not print continuous lines. The printer prints many
small drops of ink. The sintering process helps combine the silver
nanoparticles in these drops together thus creating a complete circuit. Traditionally,
the inks would have to be sintered or “baked” in an oven for a few hours so
that the solidification process would take place.[5] Chemically sintered silver
nanoparticles are dissolved in a special solvent that allows for the reaction
to take place just seconds after it is printed.[2] This dramatically reduces the
time it takes to prototype a circuit.
The only thing left is the substrate. Choosing a proper
substrate is important because it dictates how well the ink will adhere and
last. There can be a lot of experimentation still done with the substrates as
some may work better in certain situations than others. Some good baseline
substrates are resin coated paper, white and transparent PET film, inkjet
paper, and glossy photo paper.[6]
Now hook up your printer, fill and
insert your ink cartridges, and start printing!
References
[1] M. M. Tentzeris, “Inkjet-Printed
Nanotechnology-Enabled Zero-Power Wireless Sensor Nodes for Internet-of-Things
(IoT) and M2M Applications,” ATHENA Research Group, School of ECE , Georgia
Institute of Technology, Atlanta, GA, 30332-250, USA.
[2] Y. Kawahara, S.
Hodges, B. S. Cook, C. Zhang, and G. D. Abowd, “Instant inkjet circuits:
lab-based inkjet printing to support rapid prototyping of UbiComp devices,”
2013, p. 363.
[3] P. H. King, J.
Scanlan, and A. Sobester, “From Radiosonde To Papersonde: The Use of Conductive
Inkjet Printing in the Massive Atmospheric Volume Instrumentation System
(MAVIS) Project,” 2015.
[4] “NBSIJ - Silver
Nanoparticle Ink - 100ml-1,” Mitsubishi Imaging (MPM), Inc. [Online].
Available: http://diamond-jet.com/silvernanoparticleink-2.aspx. [Accessed:
28-May-2015].
[5] T. Falat, B. Platek,
and J. Felba, “Sintering process of silver nanoparticles in ink-jet printed
conductive microstructures - Molecular dynamics approach,” 2012, pp. 1/5–5/5.
[6] Y. Kawahara, S.
Hodges, N.-W. Gong, S. Olberding, and J. Steimle, “Building Functional
Prototypes Using Conductive Inkjet Printing,” IEEE Pervasive Comput.,
vol. 13, no. 3, pp. 30–38, Jul. 2014.
