Colour changing ink is our equivalent of the transistor, our ‘on and off’, ’1 and 0’.
It’s the main reason we’re able to communicate information from the internet through our paper and ink updating posters.

Whilst the electronics part of our product development process was probably the most complex. Figuring out how to print smart ink was the problem which came closest to ending the entire project.

We wanted to produce test prints in-house, before we invested in our first run of professionally printed updating posters. The plan was to convert an ink cartridge of a standard home printer so it could print colour changing ink. However, there is one small detail of this kind of ink which makes it impossible to use in the majority of print processes, both amateur and professional.

The ink particle size is just too big. As in ten to a hundred times too big for standard printer nozzles. Modern day printers have thousands of tiny nozzles per print head, and they’ve been getting smaller and smaller for decades.

After hours of scouring the internet I stumbled across this obscure article on converting a home inkjet printer into a bio-printer! There is a tiny community of tinkerers and lab workers who have figured out how to print proteins and other bio matter. They discovered a trick: use an old printer. These old printers have much bigger nozzles. Our smart ink particle size is about 10um in size. So we got to work, reading old printer data sheets, lots of fun…

We eventually managed to buy a 1990’s Epson printer from an elderly gentleman. He kept it in terrific condition too. We couldn’t believe our luck, until we discovered these nozzles were also too small.

Change of tactics

After failing to produce an in-house prototype of the print we decided to focus on figuring out how the updating poster could be printed professionally. The colour changing ink ‘pigment size’ problem carried over to this realm as well. We contacted over 30 print companies from around the globe who advertised ‘specialty ink’ printing. Yet, they were always limited to a narrow range of pre-selected inks and varnishes. No one would touch our smart ink.

In spite of all of these road blocks, we eventually hit gold. We received a tip-off about a specialty screen-printing studio in the inner suburbs of Melbourne who would apparently have a go at printing just about anything, music to our ears. We also figured out that screen-printing solves the particle size problem, as it doesn’t use tiny nozzles. It uses mesh screens, which are precise but nowhere near as small.

Over the next couple of months we worked with the studio, iterating through processes and different inks until we were happy with the print. I was originally sceptical of screen-printing as it’s quite pricey. However, the results are beautiful. We could stare for hours at the intricate grain of the paper contrasting with the vibrant paint-like finish of the ink.

Cheers,

Oli