Paper convertible into an electronic device by means of liquid metal

June 9 () –

Materials such as paper and plastic could be transformed into electronic “smart devices” using a new and easy method for applying liquid metal to surfaces.

Chinese scientists have developed a technique to apply a coating of liquid metal to surfaces that do not readily adhere to liquid metal. The method is designed to work on a large scale and may have applications in portable test stands, flexible devices, and soft robotics.

“We used to think it was impossible for liquid metal to adhere so easily to surfaces that don’t get wet, but here it can adhere to various surfaces just by adjusting the pressure, which is very interesting“, says Bo Yuan, a scientist at Tsinghua University and first author of the study, which is published in the journal ‘Cell Reports Physical Science’.

Scientists trying to combine liquid metal with traditional materials have been hampered by liquid metal’s extremely high surface tension, which prevents it from sticking to most materials, including paper.

To overcome this problem, previous research has focused primarily on a technique called “transfer printing,” which involves using a third material to bond the liquid metal to the surface. But this strategy has its drawbacks: adding more materials can complicate the process and reduce the electrical, thermal or mechanical performance of the final product.

To explore an alternative method that would allow them to directly print liquid metal onto substrates without sacrificing metal properties, Yuan and colleagues applied two different liquid metals (eGaln and BilnSn) to various silicone and silicone polymer stamps, and then applied different forces by rubbing the stamps on paper surfaces.

“At first, it was difficult to get stable adhesion of the liquid metal coating to the substrate,” Yuan explains, “However, after much trial and error, we finally got the right parameters to achieve stable and repeatable adhesion.”

They found that rubbing the liquid metal-coated stamp against the paper with a small amount of force allowed the metal droplets to effectively adhere to the surface, while applying greater amounts of force prevented the droplets from staying in place.

The team then folded the metal-coated paper into the shape of a paper crane, demonstrating that the surface could continue to fold as usual after the process was complete. And after doing so, the modified paper continues to maintain its usual properties.

While the technique looks promising, Yuan says the researchers are still figuring out how to ensure the liquid metal coating stays put once applied. For now, a packaging material can be added to the surface of the paper, but the team hopes to find a solution that doesn’t require it..

“Just like wet ink on paper can be wiped off by hand, unwrapped liquid metallic coating can also be wiped off by the object you touch when applying it,” Yuan explains. “The properties of the coating itself won’t be greatly affected. , but the objects in contact can get dirty”.

In the future, the team also plans to develop the method so that it can be used to apply liquid metal to a wider variety of surfaces, including metals and ceramics. “We also plan to build smart devices with materials treated with this method,” Yuan advances.