This Sonic Tractor Beam Costs Less Than $10

This device can push, pull, and manipulate objects through air or water using only the power of sound. It's like having a pair of acoustic tweezers, and it costs less than $10 to make. Engineers led by Kai Melde at the Max Planck Institute for Intelligent Systems in Stuttgart, Germany just developed a fascinating new way to use sound to manipulate matter. As Melde and his colleagues explain in a paper in the journal Nature, their device is almost absurdly simple. It's made out of three parts; a thin brass plate, a cheap speaker (the kind in a watch alarm), and a 3D-printed plastic disk.

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