I recently setup conductive inkjet printing at my place, and here’s the how-to:
What you require:
- Conductive ink (in my case silver nanoparticle ink)
- Inkjet printer
- Syringe and filter (comes with the ink so no need to buy separately)
- Printing sheets (available from ink manufacturers)
Selecting the ink:
To my knowledge, two companies make such ink, Mitsubishi & AgIC. As my lab used ink from Mitsubishi, I went ahead with the same ink for my further work.
Selecting the printer:
This is the trickiest part as printer companies keep changing the models and not each of them might be compatible for conductive printing. After a lot of interaction with the ink manufacturers, I could finalize a printer, and it has worked so far.🙂 The important requirements for the printer are:
- piezo inkjet head (Brother and Epson have piezo technology, while Canon,HP have thermal. Thermal technology is not preferred because heating up the ink might affect its properties, say the ink manufacturers. Nevertheless, thermal and piezo printheads both work for conductive printing (My lab has a Canon iP100, a super high res mobile photo printer.). Given both, go for a piezo printer.)
- larger nozzle size for printing (Silver particles might get clogged on smaller sized nozzles, therefore larger sized nozzles are preferred)
- empty cartridges/ink tanks and unused printing pipeline. It is important that the printer is not tested before, or filled with CMYK ink already, as it will require massive cleaning of the print head and is not preferred.
The good news is that recent inkjet printers by Brother & Epson consist of ink tanks which are initially empty and the user needs to fill the ink with appropriate ink. Thus, we are not required to look for empty cartridges which is a really really tricky task.
I had to choose between the current Brother models and Epson models available in India. The printing resolution was quite similar between Epson and Brother models. Brother models also have larger number of nozzles per color than Epson. However,Epson printers have a slightly larger nozzle size. It is hard to find out the nozzle size in diameter from the websites of the companies, but the minimun quantity of ink dispersed by the nozzle is a proportional measure of the nozzle size. For Epson, that happened to be 3pl (picoliters) and for Brother models that are currently available, it is 1.5 picoliters. AgIC recommends recent models from Epson, of which L220 was available locally. Thus, I chose L220 inkjet printer from Epson over a Brother printer majorly due to the larger nozzle sizes.
I got a pack of 100 translucent coated PET sheets from Mitsubishi. There are white PET sheets too. AgIC also has printing media available. The media is unfortunately quite expensive.
Setting up printing:
Prior to putting the ink in the printer, refrigerate it, as the recommended storage temperatures are 0-8 degrees Celcius. And once you have the ink and the printer, it’s time to put everything together.
Shake the ink well. Fill it through the syringe, insert the filter on the mouth of the syringe, and insert the syringe into the ink tank. Remove the filter, fill the ink in the syringe, put the filter back, dispense it to the ink tank and repeat.
The filter will become slower as some ink gets trapped in it during each cycle of dispensing. When it becomes too slow and hard to get the ink out of the syringe through the filter, change the filter. Yes it gets slightly messy but we don’t have to pour ink in the tank very often so please be patient.I had fortunately about 4 unused filter, of which I used 3 while filling my ink tanks. I had 100 ml of silver ink, and I put about 22 ml ink in each of the ink tanks. The ink tanks always showed low ink warning, as their capacities are 70 ml each. However, its ok to print with that much of ink within each ink tank. Once the ink is filled, then follow the setup instructions of the printer: where to place the print media, charging the ink for the first usage, etc.
Once the printer is setup, it’s time to get the first prints.Design your circuits/sensors in any circuit design software/vector graphics software. Once done, configure print settings:
- For getting more conductive traces, it is recommended that in your design all the colors(C,M,Y,K) are set to 100% (more ink material, more conductivity).
- Print media settings:
- Size: Size of the respective media, Scaling : actual size
- Type of media: Glossy photo print or closest alternative
- Quality & Resolution: Highest possible quality and resolution(printing with these settings can take slightly longer but we require high resolution so this is necessary)
Stay tuned for some fun flex sensor designs and if you are around Bangalore, for an upcoming workshop on printed sensors!🙂
- Mitsubishi Silvernanoparticle ink and print media http://diamond-jet.com/silvernanoinkjetsystem.aspx
- AgIC beginner prototyping kit https://shop.agic.cc/collections/starter-products/products/prototype-ink-kit
- AgIC circuit implementation https://agic.cc/en/industrial/ink-kit/implementation
- Instant Inkjet circuits, UbiComp 2013.
Many thanks to folks at AgIC & Mitsubishi for their support and my friends Temu,Ruchi and Viru for helping me get the ink in the short time window.🙂