Flexible sensors glide into the future with a new approach to electric printing


Scientists say a new method of “sliding” delicate high-performance electronics over flexible surfaces could allow future developments in electronics.

Engineers at the University of Glasgow say they’ve found a way to solve one of the key problems with contact printing – a method of planting electronics on bendable plastic surfaces to create circuits and devices flexible electronics.

The ability to reliably replicate the same device at high volumes is critical to the development of an electronic product and its commercialization. While contact printing techniques have been in development for more than a decade, scientists have strived to create reliable methods to bring their electronic elements and surfaces together again and again while keeping prints accurately aligned and aligned. uniformity required.

Now, in a new article published in the journal Microsystems & Nanoengineering, researchers at the University of Bendable Electronics and Sensing Technologies (BEST) describe how the introduction of sliding motion in the contact printing technique has helped them to apply nanowires to flexible and rigid surfaces with greater precision. .

The team began by fabricating zinc oxide nanowires, similar to those already used in many models of high-performance sensors, on a rigid surface in the laboratory.

They designed an automated system to transfer nanowires from their surface on which they were created – the “donor” surface – to a flexible silicon sheet – the “receiving” surface.

The system allows the team to mechanically control the movements of two flat platforms, which can rotate to ensure they line up correctly for a smooth transfer. The movement of the platforms is similar to the palms of two hands meeting and moving away from each other, with a flat object squeezed into one palm passing to the other in the process.

The donor and recipient surfaces are placed between the two platforms, which meet in a carefully controlled alignment. The system allows the team to maintain precise control over lateral and shear forces on surfaces as they meet and as they slide, which is essential for allowing the nanowire to transfer cleanly to the flexible surface.

After experimenting with the parameters of the pressure applied during the process, the team used a scanning electron microscope to scrutinize the quality of the contact impressions, which covered an area of ​​approximately 10 square centimeters on each impression.

They showed a high level of alignment uniformity of nanowires on surfaces, suggesting that the new process could be a useful next step towards large-scale contact printing of nanowires on flexible surfaces.

Professor Ravinder Dahiya from the James Watt School of Engineering at the University of Glasgow heads the BEST group.

“This is a simple but effective technique that we believe has a lot of potential to solve one of the key problems in contact printing to date,” said Prof Dahiya.

“The article discusses the system’s ability to reliably print over a relatively small area, only because we were limited by the size of the printing apparatus we built. There is every reason to expect that the same process could work on much larger surfaces, allowing the creation of flexible large-scale electronics with a level of reproducibility which was very difficult to achieve until now. .

“Although the article demonstrates the technique using zinc oxide nanowires, the method could be used to create printed integrated circuits using materials like silicon and. The new system could also support layer-by-layer printing, allowing the development of integrated circuits vertically.

“Along with this research, we have also developed a new way to reliably transfer semiconductors to flexible surfaces. The combination of our direct roll printing and new slip processes to print semiconductor micro and nanowires could open up many new applications for high performance flexible electronics.

“This could include adding a sophisticated sense of ‘touch’ to prosthetics, or the development of advanced wearable devices to accurately keep track of inpatient vital signs, or the search for new forms of self-contained digital displays. fully foldable. “

The team’s article, titled “Development of a Highly Controlled System for Large Area Directional Printing of Quasi-1D Nanomaterials”, is published in Microsystems & Nanoengineering and is available at https: //www.nature. com / articles / s41378- 021-00314-6

The research was funded by the Engineering and Physical Sciences Research Council (EPSRC).


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