Liquid-metal-based material forms airtight seal for flexible electronics
A team of researchers has developed a new material that’s not only elastic, but is impervious to gases and liquids – something that this kind of material is usually bad at. The material could be useful for making flexible batteries or wearable electronics.
Designing materials often requires trade-offs between certain properties. If you want something that’s going to keep gases and liquids out, then you’ll want a hard, stiff material. If on the other hand you need something with a bit of flexibility, then you’ll have to make do with at least some gas or liquid seeping through.
But in a new study, researchers at North Carolina State University (NCSU) have developed a new material that can do both. The key is a strange alloy known as eutectic gallium and indium (EGaIn), which is made up of those two soft metals in a form that’s liquid at room temperature. EGaIn has proved to be a versatile material – in recent years it’s been put to work as a carbon capture catalyst, in dissolvable implants, and stretchable and twistable electronic devices.
To make their new material, the team encased a thin layer of EGaIn in an elastic polymer. On the inside of the polymer was a series of tiny glass beads, which keep the EGaIn from pooling in one spot. That makes the new material a stretchy, flexible polymer with a liquid metal center that effectively prevents gases and liquids from passing through.
In tests of the material’s effectiveness, the team measured whether the liquid metal could evaporate away over time, and whether oxygen could escape from a sealed container made of the polymer. In both cases, no loss of the liquid or gas was detected, indicating it was an effective barrier.
In more detailed experiments, the researchers tested how well the polymer would work as a hermetic seal in stretchable electronic devices, including a battery and a heat transfer system. Again, the polymer helped both devices perform well in their roles, keeping the capacity of the battery high over 500 cycles and increasing the thermal conductivity of the heat transfer system.
Finally, the team added a signal transmission window to the polymer and demonstrated that it could also be used to allow wireless communication to pass through. All up, these experiments show that the flexible, non-permeable material could have a range of applications.
One possible downside is that EGaIn is relatively expensive. But the team says that there should be room to optimize the material to reduce the cost, since cost wasn’t a focus in this study. One method they suggest is to use a thinner film of EGaIn.
The research was published in the journal Science.