Photograph: Yagi Studio/Getty Images
In the basement of a University of Pennsylvania engineering building, Mohsen Azadi and his labmates huddled around a set of blinding LEDs set beneath an acrylic vacuum chamber. They stared at the lights, their cameras, and what they hoped would soon be some action from the two tiny plastic plates sitting inside the enclosure. “We didn’t know what we were expecting to see,” says Azadi, a mechanical engineering PhD candidate. “But we hoped to see something.”
Let’s put it this way: They wanted to see if those plates would levitate, lofted solely by the power of light. Light-induced flow, or photophoresis, isn’t a breakthrough on its own. Researchers have used this physical phenomenon to float invisible aerosols and sort particles in microfluidic devices. But they have never before moved an object big enough to grasp—much less lifted anything that can carry objects itself.
