Testing antibacterial surfaces on the International Space Station

Astronaut stands in front of complex equipment.
Zoom in / Because particles exhaled by astronauts can drift for some time before settling, most surfaces on the International Space Station will eventually be subject to microbial contamination.

On June 5, a SpaceX Falcon 9 rocket blasted off to the International Space Station with new equipment, including equipment for scientific research. Among the new scientific devices arriving at the ISS are four ultra-thin tablets that could play a key role in developing materials for future human space flights.

Developed by the French Atomic and Renewable Energy Commission (CEA), testing of these innovative films is part of an ongoing project to develop antibacterial materials for space habitats.

“MATISS (Microbial Aerosol Binding to Innovative Surfaces on the International Space Station) consists of exposing these tablets to the ISS environments for long periods of time to harvest the bacteria on them. These pills are then returned to our laboratories to measure the level of biocontamination,” says Sébastien Rouquet, project leader at the French space agency CNES.

A surprising number of microbes

Since the ISS is near vacuum at 400 km above Earth, it can be expected to have a sterile environment. However, according to CEA’s Guillaume Nonglaton, due to the constant presence of astronauts, the ISS is full of bacteria and fungi.

“It’s basically human bacteria [exhaled] by astronauts. Although they are not toxic, bacteria can cause health problems as well as degradation of materials and electronics when they accumulate to form biofilms. “Because of the very low gravity on the ISS, microdroplets containing bacteria can fly around for some time before sticking to various surfaces,” he said.

The MATISS project was launched in 2016 and the first set of experiments was a proof of concept. “A lot has evolved over the past seven years, including surface materials and designs, as well as laboratory analysis methods. Previously, we only used optical microscopy. Now we will also use X-ray fluorescence spectroscopy,” said Laurence Lemel of the Ecole Normale Supérieure de Lion, who is the principal investigator of the experiment.

For the upcoming mission, glass tablets covered with antibacterial surfaces are placed in four holders, each measuring 8×8×1.5 cm. Each holder has six windows through which smart surfaces are exposed to the ISS environment.

According to Lemel, the holder was designed to reduce the risk of this experiment. “We need to prevent glass lamella breakage, which can be very dangerous for astronauts on the Space Station,” he said.

Long exposure

Lemell added that for previous experiments, where the results were analyzed by optical microscopy, they used ordinary glass sheets. However, for the upcoming experiment, which will be subjected to spectroscopic analysis, the sheets are made of pure glass. “It’s pure silica quartz glass,” he said.

For a new set of experiments, three different surfaces are tested. One will have hydrophobic properties; the second is hydrophilic and the third is coated with antibacterial peptides. Like the experiment currently underway on the ISS, two of the four holders to be launched in June will last eight months and the other two will last 16 months, Rouquet said.

Rocket said the June experiment would be the last in the series. “Over the past seven years, we’ve learned a lot about the environment on the ISS and how particles are captured and controlled. “Now we are looking to develop test surfaces and hardware prototypes that can be used on spacecraft,” he said. “Our ultimate goal is to create active surfaces that not only protect astronauts, but also help reduce the time it takes to clean surfaces.”

Along with spacewalks, hardware maintenance and experiments, keeping the ISS clean is an integral task for astronauts. According to Rouquet, every Saturday, astronauts spend several hours cleaning their modules, disposing of waste and using products such as detergent and wipes to clean surfaces.

Lemell says the antibacterial materials being developed as part of the MATISS project solve another problem. “There are many instruments in structures like the space station. This instrument is stored on large shelves, which can be difficult to move. One of our goals is to have antibacterial surfaces in areas that cannot be cleaned,” Lemelle said.

Dananjay Khadilkar is a journalist based in Paris.

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