In 2021 Azadi, Popov et al. report "light-driven levitation of macroscopic polymer films with nanostructured surface as candidates for long-duration near-space flight" Using a light intensity comparable to sunlight, they levitated centimeter-scale disks made of commercial 0.5-micron-thick mylar film coated with carbon nanotubes on one side. Experiments by Schafer, Kim, Vlassak and Keith suggest that photophoretic forces could levitate thin 10 centimetre-scale structures in Earth′s stratosphere indefinitely for the purpose of atmospheric science, especially monitoring high-altitude weather. They describe in 2022 a preliminary design fabricated with available methods of a 10 cm diameter device combining a levitating structure of two membranes 2 μm apart in a stiff support structure tested to have sufficient strength to withstand transport, deployment, and flight at 25 km altitude. Payload capacity is 300 mg and could support bidirectional radio communication at over 10 Mb/s and some navigational control. By upscaling the structure it might carry payloads of a few grams. They suggest uses for telecommunications, and deployment on Mars.