A team of researchers at Harvard and the University of Chicago has created lightweight flying structures that can float using sunlight, allowing for a new window into Earth’s upper atmosphere. The mesosphere, between 50-100 kilometers above the surface, is too high for airplanes and weather balloons, but understanding this layer could improve weather forecasts and climate models.
Photophoresis, a phenomenon where gas molecules bounce off an object more forcefully on one side than the other, creates lift in extreme low-pressure environments. The researchers built thin membranes from ceramic alumina with a chromium coating to harness sunlight and create a lifting force that exceeds the structure’s weight.
The device, which is only 1 centimeter wide, was levitated at an air pressure of 26.7 Pascals when exposed to light at 55% intensity of sunlight. This pressure condition models what’s found 60 kilometers above Earth’s surface. The team envisions a range of applications, including sensing climate data, telecommunications for defense and emergency response scenarios, and Martian exploration.
The research was published in Nature and formed the basis of a Harvard spinoff company, Rarefied Technologies, launched in 2024. The team plans to integrate onboard communications payloads to enable real-time data transmission during flight.
Source: https://phys.org/news/2025-08-sunlight-powered-window-earth-upper.html