Scientists have created a new method of manufacturing flexible electronics: in it, high-performance silicon is printed directly onto flexible materials.
Glasgow University of Glasgow (BEST) Flexible Electronics and Sensor Technology engineers share how they have streamlined and improved the traditional large-area flexible electronics process. Previously, the most advanced flexible electronics were produced mainly using transfer printing: a three-step process, a bit like ink printing on documents or a visa.
First, a silicon-based semiconductor nanostructure is designed and built on a substrate. At the second stage, the nanostructure is removed from the substrate with a soft polymer stamp. At the final stage, the nanostructure is transferred from the stamp to another substrate that is especially suitable for flexible devices, for example, it can be soft robotics or a flexible display.
However, the transfer printing process has many limitations that make it difficult to create large, complex and flexible devices.
This can be compared to a poor-quality stamp in a passport, because of unprinted ink it is more difficult to read or verify it, similarly, incomplete or poor-quality polymer printing on a substrate can lead to improper operation of equipment.
So the Glasgow team took a different approach, in which they completely eliminated the second step from the typical transfer printing process. Instead of transferring the nanostructures onto a soft polymer stamp before transferring it to the final substrate, it now prints directly onto the flexible surface.
First, the engineers made a thin silicon nanostructure less than 100 nm in size. The substrate was then coated with an ultra-thin layer of chemicals to improve adhesion. The prepared substrate was wrapped around a metal tube and, then, this tube was rolled over a silicon wafer, transferring it to a flexible material.
By carefully optimizing the process, the team was able to create a very uniform print on an area of 10 cm² with a transfer yield of 95% – significantly higher than most conventional nanometer transfer printing processes.