Tiny, solar-powered floating devices that could support instruments in the high atmosphere are described in research published in Nature. The devices could be used for climate monitoring and Mars exploration, without the need for conventional fuel to maintain their altitude.
Photophoresis — a motion-generating force caused when particles suspended in a gas (or liquid) are heated by light — has been known for over a century but has only recently been explored for its practical use.
In the upper layers of the Earth’s atmosphere, where the air is very thin, photophoretic forces can be strong enough to keep small objects aloft. However, until now, most experiments have focused on very small and very light materials, and scaling up to larger, functional devices that have more practical uses has been challenging.
Benjamin Schafer and colleagues designed and built a new type of flying structure made from two thin, perforated membranes connected by tiny vertical supports the Australian science media exchange reports. Using a combination of computer modelling and laboratory experiments to optimize the photophoretic forces, they created a 1-cm-wide disk capable of levitating under light levels similar to sunlight at high altitudes.
They also proposed a 3-cm-wide version that the computer models suggest could carry a 10-mg payload (enough to support a small communications system containing a radio frequency antenna, a solar cell and integrated circuits) at an altitude of 75 km during the daytime.