Harvard team builds sunlight-powered disc to explore mesosphere

A research team from Harvard’s John A. Paulson School of Engineering and Applied Sciences has developed a lightweight, disc-shaped device powered by sunlight that can levitate in the mesosphere, the atmospheric layer between 30 and 60 miles above Earth’s surface. This region has been historically difficult to study because it lies beyond the reach of planes and balloons but below satellite orbits. The device leverages photophoresis—a physical effect where light causes gas molecules to exert a lifting force on an object in low-pressure environments—to achieve levitation. Using advanced nanofabrication, the team created centimeter-scale devices composed of thin ceramic alumina membranes and chromium layers that absorb sunlight, enabling the device to float when exposed to light under mesosphere-like conditions. The researchers tested the device in a low-pressure chamber simulating mesosphere conditions and demonstrated that a 1-centimeter-wide structure could levitate at pressures equivalent to 60 kilometers altitude with only 55% of sunlight’s intensity. This marks the