Yokohama, Japan – A protective cover made from TPU has been created for the batteries in wearable devices. Such devices have huge potential in monitoring biomarkers, for drug delivery, and as various other types of medical device. While flexible batteries have been designed, until now less attention has been paid to how they might be protected from moisture and gases.
Now, scientists at Yokohama National University have developed a stretchable packaging film for these batteries. The film has effective gas and moisture battery properties.
According to mechanical engineer Hiroki Ota, while the sensors and interfaces themselves are soft, batteries tend still to be hard. ‘Soft and stretchable batteries have been studied, but cannot be used in air due to the high gas and moisture permeability of the packaging materials of stretchable batteries,’ Ota said.
The film was created by coating a thin layer of liquid metal onto a gold-deposited TPU film, using the layer-by-layer method. This gave a deformable film with the necessary barrier properties, in contrast to the inflexible aluminium-laminated films that had previously been tried.
Its impermeability to oxygen gas and moisture was retained under mechanical strain. A test using a stretchable lithium-ion battery with the new film worked reliably in air. The hope is that will make wearable devices more practical, with stable, effective batteries that are, like the devices themselves, deformable.
The group now plans to look at whether further modifications could be made to further improve its moisture protection properties. ‘Further cost reductions of the developed film will lead to the implementation of stretchable batteries,’ Ota said. ‘In addition, the film could be useful as a barrier film for organic electronics and so on.’
The work has been published in the journal ACS Applied Materials & Interfaces.
