We've already seen a bunch of solar-panel backpacks, but now scientists are designing some luggage that harvests energy from a more immediate source. The straps for these new backpacks are made of a piezoelectric material, which means they can generate an electrical charge when stressed. If you're carrying a hefty pack and walking at a decent clip, you'll generate enough juice through the straps to power small electronic devices. And the researchers say there won't be a noticeable difference—the pack will feel the same on your shoulders.—Gregory Mone
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