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It sounds impossible: Just add water to a piece of paper and get energy. Researchers at Empa, a Swiss research institute, devised a proof of concept for a water-activated disposable battery powered by salt (dispersed in the paper) and inks containing graphite, zinc, and carbon. Its voltage, 1.2 volts, is just below what a standard AA alkaline battery offers. Within two to five years, the technology could be used in low-power single-use electronics such as medical diagnostic devices and smart packaging, says Empa’s Gustav Nyström, the inventor. “I see a new role for paper…that could also be an answer to the growing environmental concern over electronic waste,” he says.

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