Inkjet printed circuitry is a traditionally challenging endeavor, usually requiring specific silver nano-particle ink, paper, and post-proccessing through sintering. Though recent work (like this paper and this paper by researchers from The University of Tokyo) has led to streamlined and more efficient ways of fabricating instant inkjet circuits, they were restricted to relatively small range of materials, constraining the use cases to few applications — however, new work from ACM's UbiComp 2020 makes inkjet printed circuitry more accessible and usable than ever.
A team of interdisciplinary researchers from Georgia Tech, University of Tokyo, Carnegie Mellon, and University of Nebraska-Lincoln recently published a new and exciting fabrication technique that greatly expands the range of materials and use cases available for inkjet printed circuitry. The technique, called Silver Tape is a way “to transfer inkjet-printed silver traces from paper onto versatile substrates, without time-/space- consuming processes such as screen printing or heat sintering." That is to say, it effectively removes the most time and energy intensive parts of the printed circuit process while expanding the material range to include PDMS, Scotch tape, Kapton tape, and water soluble wave soldering tape.
The process starts with a desktop inkjet printer, retrofitted with ink cartridges filled with silver nano-particle ink. During printing the ink is deposited onto transfer paper — traditionally the next step would be heat sintering to ensure conductivity across the circuit, but notably this method requires no manual post-processing of that sort, rather, a chemical sintering reaction between the transfer paper and the circuit ensures conductivity right off the bat. Then, a sticky substrate is applied over the circuit, and peeled back to separate the ink from the transfer paper, giving you a new and ready to use circuit. Because the process works with a variety of materials, you can choose a substrate to meet your project needs — like Kapton for higher temperatures, or PDMS for flexibility.
The paper also highlights a workshop session the authors led to see how well students could approach the Silver Tape technique. The results showed every participant had a functional circuit within 20 minutes, highlighting the real world approachability the process has. The team proposes a few notable applications (like a printed flexible temperature sensor and ultra thin bending sensor), but most of the applications serve more to highlight the ways the Silver Tape process can be a tool in the rapid fabrication toolbox— though silver nano-particle ink isn’t cheap, it’s easy to see work flows that could benefit from Silver Tape, especially as a part of high fidelity prototypes, soft machine fabrication, paper craft, and even art making.
The paper, Silver Tape: Inkjet-Printed Circuits Peeled-and-Transferred on Versatile Substrates, by Tingyu Cheng, Koya Narumi, Youngwook Do, Yang Zhang, Tung D. Ta, Takuya Sasatani, Eric Markvicka, Yoshihiro Kawahara, Lining Yao, Gregory D. Abowd, and HyunJoo Oh, can be found in the 2020 Proceedings of the ACM on Interactive, Mobile, Wearable and Ubiquitous Technologies.