Holst Centre Accomplishes Inkjet Printing High Aspect Ratio Conductive Structures

Researchers from Holst Centre have used inkjet printing techniques to create tall, narrow conductive structures on flexible substrates for the first time. The development offers manufacturers greater production flexibility, opening the door to cheaper, higher-resolution flexible applications like OLEDs and touch screen displays. The result was presented at the latest SID ME conference in Stockholm.

The ability to create tall, narrow conductive lines on flexible structures is an important step towards high-volume roll-to-roll production of flexible electronics devices. However, while inkjet printing is well established for producing thin layers of materials, previous attempts to inkjet print high aspect ratio structures have suffered from line spreading.

To overcome this, the Holst Centre team used a carefully selected silver nanoparticle ink and repeatedly printed thin lines on top of one another to create a single tall line. The line was then cured using Holst Centre’s rapid photonic sintering technology. The final result was a line less than 100µm wide but with a resistivity of just 15mΩ per centimeter.

The work was presented at Society for Information Display Mid Europe (SID ME) Spring Meeting in May. Held in Stockholm, the meeting was organized by leading inkjet printhead supplier Xaar. Holst Centre program manager Pim Groen was a member of the organizing committee.

In addition to the work on stacked lines, the Holst Centre team presented preliminary results on a one-layer technique for inkjet printing high-aspect ratio lines. In this approach, a wide (200µm) line is printed and then contracted to just 20µm. Researcher Pit Teunissen explained that the team is also working on embedding high aspect ratio lines into the flexible substrate to produce a much flatter surface that simplifies subsequent processing steps. These embedded lines have been used successfully to create functioning OLEDs.