Engineers at the University of British Columbia created a flexible waterproof battery that is durable enough to undergo multiple wash cycles. The battery is so pliant that it can still function when stretched to double its original length. It’s made of low-cost materials, making it potentially highly suited for wearable health monitoring technology, such as items of clothing, patches, or watches that monitor vital signs.
Providing a power source for wearable tech is somewhat of a conundrum, since most batteries are delicate, non-flexible, and certainly don’t do well around fluids such as body sweat or washing machine water. These issues prompted the UBC researchers to develop a new type of battery, which is designed specifically to be included in wearables.
“Wearable electronics are a big market and stretchable batteries are essential to their development,” says Ngoc Tan Nguyen, one of the lead designers of the new battery. “However, up until now, stretchable batteries have not been washable. This is an essential addition if they are to withstand the demands of everyday use.”
Typically, batteries consists of rigid materials, but to introduce some flexibility, the research team ground up the primary components of manganese dioxide and zinc into small fragments, which they then embedded into a flexible polymer to form ultrathin sheets. These sheets were then gathered together and embedded in the same rubbery polymer, to form a waterproof coating.
The researchers chose zinc and manganese dioxide because the battery is intended to be worn near the skin, and they wanted it to be as safe as possible in the event of leakage. “We went with zinc-manganese because for devices worn next to the skin, it’s a safer chemistry than lithium-ion batteries, which can produce toxic compounds when they break,” said Nguyen.
The final result is incredibly robust, and can endure multiple wash cycles with no loss in performance. So far, the UBC researchers have subjected a battery to 39 wash cycles and it still worked. “We put our prototypes through an actual laundry cycle in both home and commercial-grade washing machines. They came out intact and functional and that’s how we know this battery is truly resilient,” said Bahar Iranpour, another researcher involved in the study.
Study in Advanced Energy Materials: Washable and Stretchable Zn–MnO2 Rechargeable Cell