New high performance silicon printing process

By on August 11, 2021 0

A new electronics production technique capable of printing high performance silicon directly onto flexible materials has the potential to make significant development in technologies such as prosthetics, fully foldable digital displays, and high-end electronics.

Image credit: University of Glasgow.

Engineers from the University of Glasgow’s Bendable Electronics and Sensing Technologies (BEST) group explained how they organized and improved the traditional process of large area flexible electronics development. The study was published in the journal Flexible electronics npj.

Until now, highly sophisticated flexible electronics have mainly been manufactured using a process known as transfer printing. This is a three-level stamping process, similar to receiving an ink stamp in a passport while visiting abroad.

Initially, a silicon-based semiconductor nanostructure is designed and built on a surface called a substrate. Then, the nanostructure is extracted from the substrate using a flexible polymer pad. Finally, the nanostructure is moved from the pad to a different flexible substrate, ready for use in foldable devices such as health monitors, foldable displays, and flexible robots.

But the transfer printing process has several limitations, which makes it difficult to manufacture more complex and large-scale flexible devices. Obtaining precise control over crucial variables such as transfer speed, as well as the adhesion and orientation of the nanostructure, made it difficult to guarantee identical pads every time.

A badly stamped passport can make it difficult for the traveler to read it; similarly, a misaligned or incomplete polymetric pad on the last substrate can provide poor electronic performance or even cause the device to malfunction.

Although the processes were developed to provide efficient stamping transfer, they mainly require additional equipment such as magnets and lasers, resulting in increased manufacturing costs.

The Glasgow team had adopted a different method, eliminating the second step of the traditional printing process. This process prints silicon directly onto a flexible surface instead of transferring nanostructures onto a flexible polymer pad before being moved to the final substrate. This new process is known as “direct roll transfer”.

The process begins with the fabrication of a thin silicon nanostructure, measuring less than 100 nm. The receiving substrate, a flexible, high performance plastic sheet material known as polyimide, is then coated with an ultra-thin layer of chemicals to improve adhesion.

The prepared substrate is then wrapped around a metal tube, and a computer-controlled machine designed by the team rolls the tube onto the silicon wafer. This makes it a flexible material.

After meticulously tuning the process, the team created very uniform prints on an area measuring approximately 10cm2, as well as a transfer efficiency of 95%. This value is remarkably higher than most traditional transfer printing processes available at the nanoscale.

Although we used a 3cm square silicon wafer sample in the process we are discussing in this article, the size of the flexible donor substrate is the only limit to the size of silicon wafers we can print. ItIt’s very likely that we can extend the process and create a very complex high performance flexible electronics, which opens the door to many potential applications..

Ravinder Dahiya, professor and BEST group leader, James Watt School of Engineering, University of Glasgow

Dahiya continued: “The performance we’ve seen from the transistors we’ve printed on flexible surfaces in the lab is similar to the performance of comparable CMOS devices, the working chips that control many everyday electronic devices.. “

This means that this kind of flexible electronics could be sophisticated enough to integrate flexible controllers into LED arrays, for example, potentially allowing the creation of self-contained digital displays that could be rolled up when not in use. Layers of a flexible material stretched over prosthetic limbs could provide amputees with greater control over their prostheses, or even incorporate sensors to give users a sense of comfort. to touch‘, Dahiya added.

This is a simpler process capable of producing flexible high performance electronics with results as good, if not better, than conventional silicon-based electronics. It is also potentially cheaper and more resource efficient, because it uses less material, and better for the environment, because it produces less waste in the form of unusable transfers..

Ravinder Dahiya, professor and BEST group leader, James Watt School of Engineering, University of Glasgow

This study was funded by the Engineering and Physical Sciences Research Council (EPSRC).

Direct roll printing for high performance electronics

Video credit: University of Glasgow.

Journal reference:

Zumeit, A., et al. (2021) Arrays of silicon nanoribbons printed by direct roll transfer based on flexible high performance electronics. flexible electronics npj.


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