It’s tricky to make robots that “swim” independently because it’s challenging for them to generate their own power underwater. A typical solution is to design bots that chemically react with water to produce bubbles that propel them, but that process tends to leave wasteful byproducts. So scientists at Shanghai’s East China Normal University have devised a novel solution: to harness the power of surface tension—a basic property of liquids—to create clean energy, instead. To prove it works, they created a “motor” that drives a number of paper cutouts around a pool of water. Right now it’s just a concept, but watch the video above to see it in action, and get an idea of where the technology could lead.