Rapid Prototyping with a $100 Inkjet Printer
By: Yash Goliya
Tags: Technology, Science Communication, Electronics, Printed Circuit Board, DIY

The real magic in this prototyping technique lies in the ink. These inks are formulated to have the right particle size so that the nozzle is not clogged and have the right viscosity for printability. Moreover, functional inks usually require heat or photonic (high-intensity light) treatment to make the printed pattern conductive. However, Mitsubishi Paper Mill’s ground-breaking ink utilized chemical sintering to make silver conductive instantly after printing without the need for further treatment. This ink is currently not available for purchase but there are some alternatives.

Although inkjet printing electronics was demonstrated decades ago, it was brought to the public eye by AgIC in 2014. The company used Prof. Yoshihiro Kawahara‘s research with Mitsubishi’s special silver ink to launch a successful Kickstarter campaign. Prof. Kawahara et. al. demonstrated several applications ranging from touch sensors to capacitive liquid level sensors in their award-winning 2014 paper.

Kickstarter Campaign by AgIC

Silver and carbon inks for desktop inkjet printers by Novacentrix are available for purchase online. Although they recommend that their silver ink patterns be treated by additional expensive equipment, it has been demonstrated that treating the silver ink on a hot plate at 100–120C produces acceptably conductive patterns. The carbon ink also requires heat treatment after printing, which is possible in an oven or hot plate. Once you have the functional inks, follow the steps by Maximus in his featured Instructables post. Just a tip: You can use conductive silver epoxy to solder circuit components instead of copper tape as used by Maximus. You need the following:

A low-cost printer such as EPSON WF 2010

Printing substrates like PET and glossy paper

Oven or hot plate for sintering & drying the ink

Empty refillable cartridges

So, what can you make or prototype with this (apart from PCBs)?

Temperature sensors based on resistance measurements

Printed temperature sensors by Liew et. al / MDPI

The resistance of a material is dependent on the temperature. Researchers from Malaysia used this concept to inkjet-print silver nanoparticles onto PET to measure temperature. They created a meander pattern and measured the resistance at the two ends. As the temperature increased, so did the resistance.

Humidity sensors based on capacitance measurements

Printed humidity sensors by Gaspar et. al. / MDPI

Researchers from VTT Technical Research Centre of Finland, inkjet-printed a pattern (interdigitated electrodes) with silver nanoparticles to measure humidity. The capacitance of this pattern changes as the humidity changes. Hence by measuring the capacitance, one can calculate the humidity.

The resolution demonstrated in this paper might not be possible with a desktop inkjet printer, but the same concept can be applied to create similar sensors with different dimensions.

Antennas for IoT applications

Printed antenna for IoT applications by Kirtania et. al. / MDPI

Antennas require a conductive material to convert electromagnetic waves into voltages and currents, and vice-versa. By changing the shape and size of the printed patterns, antennas can be designed to operate at different bands, for example, Wi-Fi or 5G frequencies.

Researchers from the Washington State University inkjet-printed this antenna on PET with a silver nanoparticle ink for IoT applications