MSGID: 1:317/3 6483fc65   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Liquid metal sticks to surfaces without a binding agent    
      
     Date:   
         June 9, 2023   
     Source:   
         Cell Press   
     Summary:   
         Everyday materials such as paper and plastic could be transformed   
         into electronic 'smart devices' by using a simple new method to   
         apply liquid metal to surfaces, according to scientists. The study   
         demonstrates a technique for applying a liquid metal coating to   
         surfaces that do not easily bond with liquid metal. The approach   
         is designed to work at a large scale and may have applications in   
         wearable testing platforms, flexible devices, and soft robotics.   
      
      
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   FULL STORY   
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   Everyday materials such as paper and plastic could be transformed   
   into electronic "smart devices" by using a simple new method to apply   
   liquid metal to surfaces, according to scientists in Beijing, China. The   
   study, published June 9 in the journal Cell Reports Physical Science,   
   demonstrates a technique for applying a liquid metal coating to surfaces   
   that do not easily bond with liquid metal. The approach is designed   
   to work at a large scale and may have applications in wearable testing   
   platforms, flexible devices, and soft robotics.   
      
   "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,"   
   said Bo Yuan, a scientist at Tsinghua University and the first author   
   of the study.   
      
   Scientists seeking to combine liquid metal with traditional materials   
   have been impeded by liquid metal's extremely high surface tension, which   
   prevents it from binding with most materials, including paper. To overcome   
   this issue, previous research has mainly focused on a technique called   
   "transfer printing," which involves using a third material to bind the   
   liquid metal to the surface.   
      
   But this strategy comes with drawbacks -- adding more materials can   
   complicate the process and may weaken the end product's electrical,   
   thermal, or mechanical performance.   
      
   To explore an alternative approach that would allow them to directly print   
   liquid metal on substrates without sacrificing the metal's properties,   
   Yuan and colleagues applied two different liquid metals (eGaln and BilnSn)   
   to various silicone and silicone polymer stamps, then applied different   
   forces as they rubbed the stamps onto paper surfaces.   
      
   "At first, it was hard to realize stable adhesion of the liquid metal   
   coating on the substrate," said Yuan. "However, after a lot of trial and   
   error, we finally had the right parameters to achieve stable, repeatable   
   adhesion."  The researchers found that rubbing the liquid metal-covered   
   stamp against the paper with a small amount of force enabled the metal   
   droplets to bind effectively to the surface, while applying larger   
   amounts of force prevented the droplets from staying in place.   
      
   Next, the team folded the metal-coated paper into a paper crane,   
   demonstrating that 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.   
      
   While the technique appears promising, Yuan noted that the researchers   
   are still figuring out how to guarantee that the liquid metal coating   
   stays in place after it has been applied. For now, a packaging material   
   can be added to the paper's surface, but the team hopes to figure out   
   a solution that won't require it.   
      
   "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," said Yuan. "The properties of the coating   
   itself will not be greatly affected, but objects in contact may be   
   soiled."  In the future, the team also plans to build on the method   
   so that it can be used to apply liquid metal to a greater variety of   
   surfaces, including metal and ceramic.   
      
   "We also plan to construct smart devices using materials treated by this   
   method," said Yuan.   
      
   This work was supported by 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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   Story Source: Materials provided by Cell_Press. Note: Content may be   
   edited for style and length.   
      
      
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   Journal Reference:   
      1. Bo Yuan, Xuyang Sun, Qianyu Wang, Hongzhang Wang. Direct   
      fabrication of   
         liquid-metal multifunctional paper based on force-responsive   
         adhesion.   
      
         Cell Reports Physical Science, 2023 DOI: 10.1016/j.xcrp.2023.101419   
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   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230609160620.htm   
      
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