A tiny aircraft powered by sunlight has been developed. The way has been opened to send it into space to observe climate change or for Mars exploration without fuel.
Professor Kim Jong-hyung of the Department of Advanced Composite Materials Engineering at Pukyong National University, along with an international research team that includes Harvard University and the University of Pennsylvania, announced on the 14th that they have developed a flight device capable of staying aloft at high altitudes for extended periods without fuel. The research was published in the international journal 'Nature' on that day.
The core principle of this device is photophoresis. This phenomenon, discovered 100 years ago, occurs when particles suspended in air or liquid receive light and one side is heated. When a temperature difference arises between the side that receives light and the opposite side, the forces that gas molecules exert on the particles change, resulting in the particles moving toward the light source or in the opposite direction.
In areas with thin air, such as the upper atmosphere of Earth, this force acts much more strongly, allowing small objects to be lifted. When the air is thin, there is almost no interference like friction when the particles move. However, previous research has focused on very small and light materials, making it difficult to extend the application to practical devices.
The research team designed a disc structure that connects two perforated thin membranes with a small pillar. When a temperature difference is created between the upper and lower parts of the device, air flows from the warm side to the cold side through the tiny holes. At this time, as the air is sucked upward in one direction through the holes, it generates the force that pushes the device upward.
Through computer simulations and actual experiments, the research team optimized photophoresis, confirming that a 1 cm diameter disc could float in the air under sunlight at the level found in the upper atmosphere. The simulation predicted that a 3 cm diameter disc structure could carry equipment weighing about 10 mg and fly 75 km above ground during the daytime under sunlight. This level can transport a small communication system that includes solar cells, wireless frequency antennas, and integrated circuits.
The research team noted that the technology using sunlight as power could be used for long-term monitoring of Earth's atmospheric conditions or for Mars exploration, where there are significant weight and power constraints. Considering that it currently costs over $100,000 (about 138 million won) to send 1 kg of equipment to Mars, the technology developed this time could significantly reduce economic burdens.
The research team stated, "In the future, it is expected that the device will evolve with navigation capabilities, greater payload capacity, and designs that allow for long-term operation, enabling it to be deployed for large-scale missions," and added, "This device, which flies using only sunlight without fuel, is expected to become a new tool for research on Earth's atmosphere and space exploration."
References
Nature (2025), DOI: https://doi.org/10.1038/s41586-025-09281-8