A ‘Lint Roller’ for Moon Dust?

The floury dust called “regolith” found on the moon’s surface is so notoriously hard to clean off that spacesuits on display at the Smithsonian are still permeated with the stuff. But researchers led by a University of Maryland aerospace engineer may have patched together a solution from a pair of distinctly earthbound inspirations: a lizard that can stick to even the smoothest surfaces when climbing and a humble gadget used to keep business and formal wear neat.

Supported by a two-year, $1.7 million NASA grant, Associate Professor Christine Hartzell and her team at the Planetary Surfaces and Spacecraft Laboratory plan to engineer and test a device similar to a lint roller—but one that uses synthetic gecko skin rather than a gluey adhesive—that astronauts can use to remove regolith from their suits and some types of equipment while working on the moon.

“We found that it picks up about 90% of the simulated lunar dust that we scatter,” Hartzell said. “It’s portable and doesn’t have to be plugged in, so astronauts can take it with them when they leave the habitat.”

It’s more than just clean-freak fussiness behind the grant. Such rollers could help alleviate regolith-related woes including the “hay fever” experienced by Apollo astronauts when they inhaled regolith inside their spacecraft, as well as changes to the thermal properties of suits and equipment that come about due to a coating of moon dust.

Actual geckos have an uncanny ability to cling to surfaces, thanks to tiny ridges in their feet that squeeze into nooks and crannies to create traction. This mechanical characteristic has previously been replicated in labs, and synthetic gecko skin has been used for various robotics applications involving gripping, but with one downfall: The material tends to get dusty and dirty.

That characteristic intrigued a doctoral student in Hartzell’s lab, Charles Pett M.S. ’21, who wondered if this defect could be turned into a feature to help astronauts clean regolith off spacesuits. Hartzell suggested marrying the gecko skin to a lint roller and making it reusable, and after undergraduate Colby Merrill ’22 ran initial tests, the project NASA is now investing in was born.

The synthetic gecko skin differs in some respects from its natural inspiration. Instead of ridges, it features tiny hairs that behave in the same way, getting into tiny spaces and sticking to dust. It’s made by applying liquid silicone to a puck-like mold, then spinning it at high speed so it spreads out and dries. The “skin” is then attached to a roller.

Hartzell and her team have already conducted lab-bench tests, using flour and later cinnamon to simulate the lunar dust—cinnamon because it’s easy to see on the white fabric used in space suits. They’ll now be utilizing a more advanced regolith simulant manufactured at the University of Central Florida’s Exolith Lab and testing the product in vacuum chambers calibrated to simulate the lunar surface.

While lint roller sheets are torn off and discarded after use, the lunar equivalents are meant to be cleaned and reused. Once astronauts return to their habitats, they’ll place the rollers inside a cleaning appliance that Hartzell’s team is now engineering. Possibilities for a cleaning method include centrifugal acceleration, in which the roller would be spun at high speed to cause the dust to fly off, or using an electron beam to charge the dust particles, which would then repel each other and detach from the roller.

A third potential approach is a NASA-developed technology known as an electrodynamic dust shield, in which wires are embedded beneath the gecko skin membrane; an electric field would then be generated, again causing the dust to fly off.

To ensure the simulated gecko skin can stand up to the rigors of the moon, Professor David Akin, director of the Space Systems Laboratory, will conduct thermal testing to simulate lunar temperatures, which range from an ultra-cold 298 degrees below Fahrenheit at night to a sizzling 224 degrees during the day.

The rollers can’t be used on all surfaces: They wouldn’t be a good choice for optical surfaces, for instance, since the “hairs” of the gecko skin could cause scratching. But in addition to suits, they could be used on other, less sensitive pieces of equipment like solar panels, Hartzell said.