Material scientists have made an extraordinary breakthrough in 2D materials, by inventing an ultra-flexible electrical material for use in touchscreens that can be printed and rolled out like newspaper.

Unlike current touchscreen materials, which are 3D, the new material is 100 times thinner, so it lets more light pass through, making it more energy efficient.

“This means a cell phone with a touchscreen made of our material would use less power,” explains the study’s lead researcher Dr Torben Daeneke, “extending the battery life by roughly 10%.”

The research team of Dr Robi Datta, Dr Torben Daeneke, and Dr Nitu Syed. 

The discovery was based on modifying current technology for touchscreen production, which is slow and make screens in batches, and replace it with a material that is lighter, more flexible, and can be made on a roll to roll (2R) production process.

At first, the team studied regular touchscreens, which are typically made of indium-tin oxide, a transparent yet brittle material. By applying liquid-metal chemistry to the material, the team were able to shrink the 3D substance to only 2D. This left the researchers with a material flexible enough to be rolled up into a tube.

“We've taken an old material and transformed it from the inside to create a new version that's supremely thin and flexible,” says Daeneke, an Australian Research Council DECRA Fellow at RMIT. “You can bend it, you can twist it, and you could make it far more cheaply and efficiently than the slow and expensive way that we currently manufacture touchscreens.”

In fact, the process is much simpler than the energy intensive, vacuum chamber, batch production as Daeneke highlights, “The beauty is that our approach doesn't require expensive or specialised equipment - it could even be done in a home kitchen.”

The process was outlined in the RMIT press release, which explained how the researchers used a liquid metal printing approach to create atomically-thin indium-tin oxide (ITO). The report describing how, “An indium-tin alloy is heated to 200C, where it becomes liquid, and then rolled over a surface to print off nano-thin sheets of indium tin oxide.”

Schematic of the developed two-terminal resistive test device, with the inset showing the ITO/polymer interface.

While these 2D nano-sheets have the same chemical make-up as regular touchscreen raw material, the ingredients now have a new crystal structure, giving them novel optical and mechanical properties.

Consequently, the report notes, “As well as being fully flexible, the new type of ITO absorbs just 0.7% of light, compared with the 5-10% of standard conductive glass. To make it more electronically conductive, you just add more layers.”

a) AFM image of the 2D nanosheet. The inset shows a height profile recorded at the location indicated by the black line. b) Low-resolution TEM image of an ITO nanosheet printed onto a TEM grid.

It's a pioneering approach that cracks a challenge that was considered unsolvable, Daeneke said.

“There's no other way of making this fully flexible, conductive and transparent material aside from our new liquid metal method,” says Daeneke. “It was impossible up to now - people just assumed that it couldn't be done.”

The study was a collaboration of material analysis, with researchers from RMIT, Monash University, the ARC Centre of Excellence in Future Low-Energy Electronics Technologies (FLEET), and UNSW. The final report has now been published in the journal Nature Electronics, where they describe in detail how they created a, “… capacitive touch screen using centimetre-sized monolayer ITO sheets.”

a) An indium–tin alloy droplet is placed onto a suitable substrate, which is heated to 200 °C. A second preheated substrate is gently pressed from the top. b) Cross-sectional view of the squeezed alloy placed between the two substrates, pressing the liquid metal into a thin metallic film. The crystal structure of ITO can be seen in the inset. c) When the top substrate is lifted, the liquid metal reverts to small spherical droplets due to its high surface tension, revealing large-area ITO. d) LED demonstration circuit utilizing the printed 2D ITO to bridge a gap in the LED power circuit. The 2D ITO is visibly transparent and sufficiently conductive to allow for the LED to be switched on.

For now, the team have built working touchscreens, as a proof-of-concept, with the technology still patent pending.

However, the research is continuing, with the team exploring how their new approach to 2D material production could be applied to other optical electronic devices, such as touch displays, solar panels, LEDs, and even smart windows.

With so many possibly applications, the team are also considering the best way forward to commercialise the discovery.

“We're excited to be at the stage now where we can explore commercial collaboration opportunities and work with the relevant industries to bring this technology to market.” Says Daeneke.

These are changing times for the electronics industry, with new materials and technologies being constantly developed. However, all too often, breakthroughs are made that are too futuristic, too expensive, too incredible, or require current electrical products to be adapted before the new technology can be implemented.

However, by developing a roll on roll production process for more energy efficient and lighter touchscreens that can be immediately installed into next year’s mobile phones, this study has found something both futuristic and practical.  

As Daeneke concludes, “We've shown its possible to create printable, cheaper electronics using ingredients you could buy from a hardware store, printing onto plastics to make touchscreens of the future.”

Photo credit: Offgridindependce, Guardian, Nature, & RMIT