Researchers reach new heights with light-based levitation

Researchers in the Bargatin Group, from the lab of Igor Bargatin, associate professor in the School of Engineering and Applied Science’s Department of Mechanical Engineering and Applied Mechanics, is working to engineer nanoscale features on ultra-lightweight materials, finding the ideal combination that will allow those materials to lift themselves into the air using the energy provided by light.

Mohsen Azadi wears latex gloves and wields a scalpel while preparing a photophoretic levitation experiment.
Working in the Bargatin Group’s lab, Mohsen Azadi wields a scalpel while preparing a photophoretic levitation experiment. Unlike the microscopic particles that have been previously levitated with this techniques, the researchers’ flyers are big enough to manipulated by hand. (Image: Eric Sucar)

This method of propulsion, known as photophoretic levitation, is not a new concept, but it has mostly been applied to microscopic objects. Bargatin and his colleagues, however, have demonstrated its potential for use in atmospheric probes by lifting small payloads with their “nanocardboard” flyers. Like paper cardboard, these ultra-thin plates of aluminum oxide gain stiffness from internal corrugations, but those corrugations also shoot air through the plate’s hollow structure when they’re heated by light, allowing them to achieve lift.

In their latest study, published in Science Advances, Bargatin, lead author Mohsen Azadi and their colleagues have demonstrated their most stable photophoretic levitation yet. It’s another step closer to using their flyers to probe the mesosphere, the region of Earth’s atmosphere at the edge of outer space.

The flyers in the team’s new paper have a different design than their nanocardboard ones, though they still take advantage of nanoscale features. These flyers are centimeter-wide discs that have a 500-nanometer-thin film of Mylar on top and a forest of carbon nanotubes pointing downward. The heat differential produced by shining bright light on the discs is enough to get air molecules to jet downward from the hotter underside, thrusting the disc into the air.

Read more at Penn Engineering Today.