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Small tray levitated using nothing but light, with goal to reach mesosphere

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https://www.wired.com/story/researchers-...but-light/

EXCERPT: . . . 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.

And it worked. “When the two samples lifted,” Azadi says, “there was this gasp between all four of us.” The Mylar plates, each as wide as a pencil’s diameter, hovered thanks to nothing but the energy from the light below, according to a paper published today in Science Advances. Energy from the LEDs heats up the Mylar’s specially-coated underbelly, energizing air particles under the plastic and propelling the plates away with a tiny, but mighty, gust.

This engineered structure is the first instance of stable photophoretic flight, and Azadi’s accompanying theoretical model can simulate how different flying plates would behave in the atmosphere. In particular, the model indicates that a levitating plate could mosey 50 miles overhead while carrying sensor-sized cargo. It’s an idea the lab members have floated as a way to study weather and climate—although atmospheric scientists say the idea is still preliminary and will face some daunting meteorological challenges.
Courtesy of Mohsen Azadi

There’s a reason why scientists would want to get a tiny sensor into the under-explored mesosphere, which lies between 31 and 53 miles above your head. “Sometimes it's called ignorosphere, in joke,” says Igor Bargatin, a mechanical engineering professor at Penn and Azadi’s adviser, who led the study. “We just don't have access to it. You can send a rocket for a few minutes at a time, but that's very different from doing measurements using airplanes or balloons.”

We haven’t ignored the mesosphere because it’s uninteresting; we’ve ignored it because it’s out of reach. The denser air below it affords enough lift to planes and balloons. And the thermosphere above is thin enough that air drag doesn’t burn orbiting satellites. The mesosphere gets the worst of both worlds—it’s too thin for lift but thick enough to burn an orbiter.

That’s a drag for scientists, because the mesosphere is loaded with interesting phenomena... (MORE - details)
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