THE University of British Columbia (UBC) researchers have created what could be the first battery that is both flexible and washable. It works even when twisted or stretched to twice its normal length, or after being tossed in the laundry. The battery developed by Ngoc Tan Nguyen, a postdoctoral fellow at UBC’s faculty of applied science, and his colleagues offers a number of engineering advances. In normal batteries, the internal layers are hard materials encased in a rigid exterior. The UBC team made the key compounds — in this case, zinc and manganese dioxide — stretchable by grinding them into small pieces and then embedding them in a rubbery plastic, or polymer. The battery comprises several ultra-thin layers of these polymers wrapped inside a casing of the same polymer. This construction creates an airtight, waterproof seal that ensures the integrity of the battery through repeated use. It was team member Bahar Iranpour, a Ph.D. student, who suggested throwing the battery in the wash to test its seal. So far, the battery has withstood 39 wash cycles and the team expects to further improve its durability as they continue to develop the technology. The choice of zinc and manganese dioxide chemistry also confers another important advantage. “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,” says Nguyen. “The materials used are incredibly low-cost, so if this is made in large numbers, it will be cheap,” says electrical and computer engineering professor John Madden, director of UBC’s Advanced Materials and Process Engineering Lab. (SD-Agencies) | 