A groundbreaking technique has been developed by researchers, enabling the application of liquid metal to everyday surfaces like paper and plastic. This breakthrough has the potential to convert these materials into electronic “smart devices.” The researchers aim to expand the scope of this method to a wide range of surfaces and utilize it for constructing smart devices using treated materials.
Chinese scientists have successfully devised a method to coat ordinary materials, such as paper and plastic, with liquid metal, creating the possibility of producing “smart devices.” Unlike previous challenges due to high surface tension, this approach adjusts pressure instead of relying on binding materials, effectively allowing liquid metal to adhere to surfaces.
According to scientists in Beijing, China, a simple and novel method can transform everyday materials, including paper and plastic, into electronic “smart devices.” A study published in the journal Cell Reports Physical Science on June 9th outlines a technique for applying liquid metal coatings to surfaces that typically do not bond well with liquid metal. This method has the potential to be used on a large scale and find applications in wearable testing platforms, flexible devices, and soft robotics.
Bo Yuan, a scientist at Tsinghua University and the study’s first author, expressed his excitement, stating, “Previously, we believed it was nearly impossible for liquid metal to adhere so easily to non-wetting surfaces. However, this method allows for adhesion to various surfaces simply by adjusting the pressure, which is incredibly fascinating.”
Combining liquid metal with conventional materials has been a challenge due to the high surface tension of liquid metal, which makes it difficult to bind with most materials, including paper. Prior research primarily focused on a technique called “transfer printing” to overcome this issue, where a third material is used to bind the liquid metal to the surface. However, this approach has drawbacks, such as complicating the process and potentially compromising the electrical, thermal, or mechanical performance of the final product.
To explore an alternative approach that directly prints liquid metal on substrates without compromising its properties, Yuan and his colleagues experimented with two different liquid metals (eGaln and BilnSn) on various silicone and silicone polymer stamps. They applied different forces while rubbing the stamps onto paper surfaces.
“At first, achieving stable adhesion of the liquid metal coating on the substrate was challenging,” explained Yuan. “However, after extensive trial and error, we finally identified the correct parameters for achieving stable and repeatable adhesion.”
The researchers discovered that rubbing the liquid metal-covered stamp against the paper with a small amount of force effectively bonded the metal droplets to the surface. On the other hand, applying excessive force prevented the droplets from remaining in place.
Next, the team folded the metal-coated paper into a paper crane, demonstrating that the surface could be folded normally after the process. Importantly, the modified paper retained its original properties.
While the technique shows promise, Yuan mentioned that ensuring the liquid metal coating remains in place after application is still an ongoing challenge. Currently, a packaging material can be added to the paper’s surface, but the team hopes to find a solution that eliminates this requirement.
“Just as wet ink on paper can be wiped off by hand, the liquid metal coating applied here without packaging can also be wiped off by contact with other objects,” explained Yuan. “While the coating’s properties are not significantly affected, the objects it comes into contact with may become soiled.”
In the future, the researchers plan to further develop this method to enable the application of liquid metal on a broader range of surfaces, including metal and ceramic.
“We also intend to utilize materials treated by this method to construct smart devices,” added Yuan.
Reference: “Direct fabrication of liquid-metal multifunctional paper based on force-responsive adhesion” by Yuan et al., 9 June 2023, Cell Reports Physical Science.
DOI: 10.1016/j.xcrp.2023.101419
This work received support from the China Postdoctoral Science Foundation, the National Nature Science Foundation of China, and the cooperation funding between Nanshan and Tsinghua SIGS in science and technology.
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Frequently Asked Questions (FAQs) about liquid metal applications
What is the significance of the liquid metal breakthrough described in the text?
The liquid metal breakthrough described in the text is significant because it allows everyday materials like paper and plastic to be transformed into electronic “smart devices.” This opens up possibilities for the integration of electronic functionalities into a wide range of objects and surfaces.
How does the method of applying liquid metal to surfaces work?
The method involves adjusting pressure instead of using a binding material to enable the liquid metal to adhere to surfaces. By rubbing liquid metal-covered stamps with the right amount of force onto materials like paper, the metal droplets effectively bind to the surface.
What challenges did researchers face in applying liquid metal to non-wetting surfaces?
Researchers faced challenges due to the high surface tension of liquid metal, which prevented it from bonding well with most materials, including paper. Previous techniques like transfer printing required the use of additional materials, complicating the process and potentially affecting the performance of the final product.
Can the liquid metal coating be applied to other materials besides paper and plastic?
While the research focused on applying liquid metal to paper and plastic, the researchers aim to expand the method’s application to a greater variety of surfaces, including metal and ceramic. This could potentially lead to the creation of smart devices using a wide range of materials.
How can the liquid metal coating be made to stay in place after application?
Currently, a packaging material can be added to the surface to ensure the liquid metal coating remains in place. However, the researchers are actively working to find a solution that eliminates the need for additional packaging and maintains the stability of the coating without compromising its properties.
More about liquid metal applications
- Cell Reports Physical Science: Direct fabrication of liquid-metal multifunctional paper based on force-responsive adhesion
- China Postdoctoral Science Foundation: Official website
- National Nature Science Foundation of China: Official website
