On June 5, a SpaceX Falcon 9 rocket blasted off to the International Space Station with new supplies, including equipment for scientific research. Among the new scientific gear that has arrived at the ISS are four tablets covered with extremely thin films that could play a crucial role in the development of materials for future human space flights.

Testing these innovative films, which were developed by the French commission for atomic and renewable energy (CEA), is part of an ongoing project aimed at developing antibacterial materials for space habitats.

“MATISS (Microbial Aerosol Tethering on Innovative Surfaces in the International Space Station) consists of exposing these tablets in the ISS environments for a long time in order to collect the bacteria that gets deposited on them. These tablets are then returned to our laboratories for measuring the level of biocontamination,” says project manager Sebastien Rouquette of the French space agency CNES.

A surprising number of microbes

With the ISS being 400 km above the Earth in a near-vacuum, one might expect it to have a sterile environment. However, according to Guillaume Nonglaton of the CEA, thanks to the constant presence of astronauts, the ISS is teeming with bacteria and fungi.

“It’s mainly human bacteria [exhaled] by the astronauts. Although they are not toxic, the bacteria can cause health care issues as well as degradation of materials and electronics if they accumulate to form biofilms. Since there is very low gravity in the ISS, the microdroplets containing bacteria fly around for quite some time before attaching to different surfaces,” he said.

The MATISS project was launched in 2016, and the first set of experiments served as proof of concept. “A lot has evolved over the past seven years including in the surface materials and designs as well as laboratory analysis techniques. Earlier, we were using only optical microscopy. Now, we will be using X-ray fluorescence spectroscopy, too,” Laurence Lemelle of Ecole Normale Supérieure de Lyon, who is the experiment’s principal investigator, said.

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

According to Lemelle, the holder was designed to minimize the risk posed by this experiment. “We need to avoid the breakage of the glass lamella, which can be very dangerous for the astronauts on the Space Station,” she said.

Long exposure

Lemelle added that for earlier experiments where the results were analyzed using optical microscopy, they used regular glass sheets. However, for the upcoming experiment, which will be subjected to spectroscopic analysis, the sheets are made of pure glass. “It's quartz glass made of pure silica,” she said.

For the new set of experiments, three different surfaces will be tested. One will have hydrophobic properties; the second is hydrophilic, while the third is coated with antibacterial peptides. According to Rouquette, just like the experiment currently running on the ISS, two of the four holders that will be sent in June will be exposed for eight months, and the other two for 16 months.

Rouquette said the June experiment will be the last in this series. “Over the past seven years or so, we have acquired good knowledge of the environment in the ISS and the way to catch and observe particles. We will now be looking to develop test surfaces and prototypes of hardware that could be used in spacecraft,” he said. “Our eventual goal is to build active surfaces that would not only protect astronauts but also help them in reducing the time needed for cleaning the surfaces.”

Along with spacewalks, hardware maintenance, and conducting experiments, keeping the ISS squeaky clean is an integral activity for astronauts. According to Rouquette, every Saturday, astronauts spend hours cleaning their modules, trashing waste, and using products such as detergent and wipes to clean the surfaces.

Lemelle says that the antibacterial materials being developed as part of the MATISS project will address another problem. “In structures like the space station, there is a lot of instrumentation. This instrumentation is stored in huge racks, which can be difficult to move. One of our goals is to have antibacterial surfaces in regions that cannot be cleaned,” Lemelle said.

Dhananjay Khadilkar is a journalist based in Paris.