Engineers improve the conventional process for printing large-scale, complex flexible electronics.
Flexible electronics can be employed in a myriad of applications, including health monitors, soft robotics, and bendable displays.. There have been recent developments in this field for creating fully flexible high-performance sensors and displays.
Now, most flexible electronics are implemented by a process called transfer printing, which is a three-stage stamping-like process. In this process, first of all, silicon-based nanostructure is designed and grown on a surface known as a substrate. Then the nanostructure is picked up from the substrate by a soft polymeric stamp. Finally it is transferred from a stamp to a flexible substrate.
This process, however, has many limitations that limit the progress of large-scale flexible devices. Precisely controlling critical variables like the speed of transfer, and the adhesion and orientation of the nanostructure, makes it difficult to ensure each stamp is identical to the last.
Engineers from the University of Glasgow’s Bendable Electronics and Sensing Technologies (BEST) group have described how they improved the conventional approach for creating flexible electronics. They removed the second stage of fabrication in conventional processes altogether, and instead introduced their new process, what they call ‘direct roll transfer’ to print silicon straight onto a flexible surface.
The process consists of fabrication of thin silicon nanostructure of less than 100 nanometers to improve adhesion and precise control.
Professor Dahiya, leader of the BEST group at the University of Glasgow’s James Watt School of Engineering, said: “Although we used a square silicon wafer sample of 3cm on each side in the process we discuss in this paper, the size of the flexible donor substrate is the only limit on the size of silicon wafers we can print. It’s very likely that we can scale up the process and create very complex high-performance flexible electronics, which opens the door to many potential applications.
“The performance we’ve seen from the transistors we’ve printed onto flexible surfaces in the lab has been similar to the performance of comparable CMOS devices—the workhorse chips which control many everyday electronics.”
“That means that this type 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 which could be rolled up when not in use. Layers of flexible material stretched over prosthetic limbs could provide amputees with better control over their prosthetics, or even integrate sensors to give users a sense of ‘touch.”
The research appeared in the npj Flexible Electronics journal.