Everyday materials – such as paper and plastic – could be transformed into “smart” devices such as mobile phones after the development of a liquid metal that sticks.
Scientists say the technology has potential applications in wearable electronics, soft robotics and flexible devices such as stretchable smartphones.
First author Dr. Bo Yuan, of Tsinghua University in China, said: “Before, we thought that it was impossible for liquid metal to adhere to non-wetting surfaces so easily.
“But here it can adhere to various surfaces only by adjusting the pressure, which is very interesting.”
The Chinese team demonstrated a technique for applying it to surfaces that do not easily bond. The approach described in Cell Reports Physical Science is designed to be scaled up for mass production.
Previous attempts have been impeded by liquid metal’s extremely high tension, which prevents it from adhering to most materials, including paper. To overcome the issue, a strategy called ‘transfer printing’ has been tried which involves using a third material. But drawbacks include complicating the process and weakening the end product’s electrical, thermal or mechanical performance.
Dr. Yuan and colleagues’ alternative method used a cocktail of liquid metals called eGaln and BilnSn. They were applied to various silicone stamps, that were then rubbed onto paper surfaces.
Dr. Yuan said: “At first, it was hard to realize stable adhesion of the liquid metal coating on the substrate.
“However, after a lot of trial and error, we finally had the right parameters to achieve stable, repeatable adhesion.”
Rubbing the stamp against the paper with a small amount of force enabled metal droplets to bind effectively to the surface. Applying greater energy prevented the droplets from staying in place. Making an origami-style paper crane demonstrated the surface can still be folded as usual after the process is completed. And after doing so, the modified paper still maintains its usual properties.
The researchers described the results as “promising.” They are still figuring out how to guarantee that the liquid metal coating stays in place after it has been applied. For now, packaging material can be added to the paper’s surface, but the team hopes to figure out a solution that won’t require it.
Dr. Yuan said: “Just like wet ink on paper can be wiped off by hand, the liquid metal coating without packaging here also can be wiped off by the object it touches as it is applied. The properties of the coating itself will not be greatly affected, but objects in contact may be soiled.”
In the future, the researchers plan to apply liquid metal to a greater variety of surfaces, including metal and ceramic.
Added Dr. Yuan: “We also plan to construct smart devices using materials treated by this method.”
Bendable displays are an emerging technology, ranging from foldable smartphones to bendy TVs and curved public information displays.
The latest findings could help take them to the next level. The future of technology is moving away from flat, rigid displays and towards more flexible and curved alternatives.
Produced in association with SWNS Talker
Edited by Jessi Rexroad Shull and Kyana Jeanin Rubinfeld
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