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The material – which could be used as packaging for high-value technologies that require protection from gases, such as flexible batteries – was developed by researchers at North Carolina State University and Shanghai Jiao Tong University in China.
“This is an important step because there has long been a trade-off between elasticity and being impervious to gases,” said Professor Michael Dickey from NC State, co-corresponding author of a paper on the work.
“Basically, things that were good at keeping gases out tended to be hard and stiff. And things that offered elasticity allowed gases to seep through. We’ve come up with something that offers the desired elasticity while keeping gases out.”
The technique to make the new material uses a eutectic alloy of gallium and indium (EGaIn), meaning the alloy has a melting point that is lower than its constituent parts – in this case, the EGaIn is liquid at room temperature.
The researchers created a thin film of EGaIn, and encased it in an elastic polymer. The interior surface of the polymer was studded with microscale glass beads, which prevented the liquid film of EGaIn from pooling. The result is an elastic bag or sheath lined with liquid metal, which does not allow gases or liquids in or out.
The team tested the effectiveness of the new material by assessing the extent to which it allowed liquid contents to evaporate, as well as the extent to which it allowed oxygen to leak out of a sealed container made of the material.
“We found that there was no measurable loss of either liquid or oxygen for the new material,” said Professor Tao Deng, co-corresponding author from Shanghai Jiao Tong.
“The liquid metals themselves are fairly expensive,” Deng added. “However, we’re optimistic that we can optimise the technique – for example, making the EGaIn film thinner – in order to reduce the cost. At the moment, a single package would cost a few dollars, but we did not attempt to optimise for cost, so there is a path forward to drive cost down.”
The researchers are exploring testing options, to determine whether the material is actually an even more effective barrier than they have been able to show so far.
“Basically, we reached the limit of the testing equipment that we had available,” Dickey said.
“We’re also looking for industry partners to explore potential applications for this work. Flexible batteries for use with soft electronics is one obvious application, but other devices that either use liquids or are sensitive to oxygen will benefit from this technology.”
The work, which also involved authors from A123 Systems in China, will be published in Science.
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