EPS Colloquium – Ben Schafer, Rarefied Technologies

Photophoretic Flyers: Novel Propulsion for Exploring Near-Space

While photophoresis, or “light-driven motion,” has long explained how aerosol layers remain aloft in the upper atmosphere, practical applications have only recently been gaining attention. Advances in nanofabrication now allow us to build devices that are much larger than aerosols but lightweight enough to propel themselves upward using photophoretic forces alone. These devices could sustain flight in near-space (30-100 km altitudes), a region of our atmosphere which is too high for aircraft and balloons to fly, but too low for satellites to orbit. I will discuss the physics of photophoresis, how it arises from temperature and material-property gradients on a surface, and recent experimental tests and models that demonstrate its viability for near-space propulsion. I will also outline potential applications, including atmospheric and space weather data collection, telecommunications, and exploring Mars’s atmosphere.

To be added to the EPS colloquium mailing list, please contact Caroline Carr at carolinecarr@fas.harvard.edu

Ben Schafer is the CEO and Co-Founder of Rarefied Technologies and an Associate Researcher in Prof. Joost Vlassak’s group at Harvard SEAS. His research focuses on innovative designs for photophoretically flying structures, the experimental fabrication and testing of flying devices, and the application of this technology to address challenges in atmospheric and space science, remote sensing, and telecommunications. He received his Ph.D. in Applied Physics from Harvard in 2024, and he is currently a Breakthrough Energy Fellow and a New Mexico LEEP Fellow.