Engineers from the University of Glasgow's Flexible Electronics and Sensing Technology (BEST) group explain how they
First, a semiconductor nanostructure basedsilicon is designed and made on a substrate. At the second stage, the nanostructure is removed from the substrate using a soft polymer stamp. In the final step, the nanostructure is transferred from the stamp to another substrate that is specifically suitable for flexible devices, such as 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 low-quality stamp inpassport, due to unprinted ink it is more difficult to read or verify, similarly, incomplete or low-quality polymer printing on the substrate can lead to improper operation of the equipment.
Therefore, the Glasgow team used a differentapproach, in which she 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, engineers made thin siliconnanostructure with a size of less than 100 nm. Then they coated the substrate 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 tocreate a very uniform print on an area of 10 cm² with a transfer yield of 95% - significantly higher than most conventional nanometer-scale transfer printing processes.
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