Soft materials are highly permeable to gases, making it difficult to create stretchable hermetic seals. An often overlooked aspect of stretchable electronics and technology is the choice of materials to protect them hermetically.
An international team of researchers developed a technique that uses liquid metal to create an elastic material impervious to gases and liquids.
A eutectic alloy of gallium and indium (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. The scientists produced a thin coating of EGaIn, and 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 result is a liquid metal-lined elastic bag or sheath impermeable to gases and liquids.
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 could determine how effective the material was.
Tao Deng, co-corresponding author and Zhi Yuan Chair Professor at Shanghai Jiao Tong University, said, “We found that there was no measurable loss of either liquid or oxygen for the new material.”
“The liquid metals themselves are fairly expensive. However, we’re optimistic that we can optimize the technique – for example, making the EGaIn film thinner – 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.”
Researchers reported that the material could be used in packaging for high-value technologies that require protection from gases, such as flexible batteries.
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, said, “This is an important step because there has long been a trade-off between elasticity and being impervious to gases.”
“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 created something that offers the desired elasticity while keeping gases out.”
The researchers are currently exploring testing options to determine whether the material is an even more effective barrier than they’ve been able to show so far.