Researchers made zinc batteries flexible and stretchable by incorporating a hyper-elastic polymer layer made from isoprene, which is one of the main ingredients in rubber, and polystyrene. This substance allowed the batteries to stretch to twice their size without damage.
The scientists tested the technology on a fabric (see picture above, or video) but future steps could include expanding its use to different applications such as solar cells, or using it to power different kinds of electronic devices.
The team, from the university’s Center for Wearable Sensors, also managed to make the batteries rechargeable by adding bismuth oxide to the ink alongside zinc silver oxide. “This is a significant step toward self-powered stretchable electronics,” said Joseph Wang, a senior author on the paper. “We expect this technology to pave the way to enhance other forms of energy storage and printable, stretchable electronics, not just for zinc-based batteries but also for lithium-ion batteries, as well as supercapacitors and photovoltaic cells.”
The prototype battery developed by the researchers has about one fifth of the capacity of a rechargeable hearing aid battery, but is one tenth as thick, and cheaper to make. Currently it takes two of these batteries to power a 3 Volt LED, but researchers are working to improve its performance.
One potential use could be wearable sensors for medical purposes, either attached to the skin or implanted inside the body, according to Niko Munzenreider, a lecturer in sensor technology at the University of Sussex, who was not involved in the research. “Medical purposes for sure the most obvious ones,” he told Professional Engineering. “You can fabricate smart tattoos to monitor different parameters like temperature, PH, chemicals, things like this.”
The human body presents a challenging environment for electronics, he added. “It has to be biocompatible, you cannot use poisonous materials for example. But the more challenging part is probably the material science point of view, because first of all it has to be stretchable, and human skin is stretchable by up to 70 %.”
This new breakthrough could solve a lot of problems, according to Munzenreider. “You don’t have to rely on solar cells and energy harvesting anymore – you can use this variable device in an environment where you cannot harvest energy, for example during the night, or inside the body.”