A method that uses liquid metal to make an elastic material that is impenetrable to both gases and liquids has been created by an international team of researchers. The material can be used to package valuable technology that needs to be protected from gases, including flexible batteries.
“This is an important step because there has long been a trade-off between elasticity and being impervious to gases,” says Michael Dickey, co-corresponding author of a paper on the work and the Camille & Henry Dreyfus Professor of Chemical and Biomolecular Engineering at North Carolina State University. “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.”
A gallium-indium eutectic alloy (EGaIn) is used in the novel method. Eutectic refers to an alloy with a lower melting point than its component elements. The EGaIn is liquid at room temperature in this instance. A thin coating of EGaIn was produced by the researchers, who then covered it with an elastic polymer. Glass microbeads were placed on the polymer's internal surface to prevent the liquid coating of EGaIn from pooling. The end result is essentially a liquid metal-lined elastic bag or sheath that is impermeable to gases and liquids, reports Matt Shipman at NCSU News.
By measuring how much liquid content was allowed to evaporate and how much oxygen was permitted to escape from a sealed container made of the novel material, the researchers were able to determine how successful the material was. “We found that there was no measurable loss of either liquid or oxygen for the new material,” says Tao Deng, co-corresponding author and Zhi Yuan Chair Professor at Shanghai Jiao Tong University.
The researchers are also conscious of the costs associated with manufacturing the new material. “The liquid metals themselves are fairly expensive,” Deng says. “However, we’re optimistic that we can optimize 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 optimize for cost so there is a path forward to drive cost down.”
The researchers are currently exploring testing options to determine whether the material is actually an even more effective barrier than they’ve been able to show so far. “Basically, we reached the limit of the testing equipment that we had available,” Dickey says. “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.”