Biocontamination in manned spacecrafts and in future habitats could have significant impacts on crew health and biodegradation of equipment. Although there are no reported microbiological events onboard that had a critical impact on the crew, multiple reported contamination events indicate that the current prevention, monitoring and mitigation methods have to be optimized and new methods need to be considered.
In particular, there is a need for decreasing the dependency of crew action for cleaning actions, while being more efficient and reliable. The current cleaning strategy consists in manually wiping the contaminated surface with disinfectants. In addition of being time consuming and laborious, this method requires the use of chemicals that can release toxic particles in the air. Furthermore, it has been demonstrated that microorganisms can develop resistance to the used disinfectants. Finally, an accumulation of biocontamination has been observed in hardly accessible areas, such as behind the racks or next to the pumps and water pipes. To reach and wipe these areas with good efficiency can be complicated. In this context, anti-microbial surfaces that inhibit or reduce the ability of microorganisms to grow on the surfaces are of high interest.
MATISS-2 and MATISS-2.5 experiments aims to demonstrate that surfaces with hydrophobic properties could be a possible answer applicable on the scale of spacecraft. The hydrophobic covers are indeed already implemented in numerous industrial fields (aeronautics, housing environment, textile, optometry, automobile, medical). By reducing the contact area of the droplets of water with surfaces, the hydrophobicity allows at the first order to limit the fraction of surface which is contaminated. It also limits the adhesion of microorganisms to surfaces.
Justification for Need of Space Experiment
Antimicrobial surfaces are currently used on Earth in a number of sectors, such as healthcare, food industry, water industry, textiles. Consequently, numerous tests and standards exist for evaluating antimicrobial surfaces for terrestrial applications. However, they are not being adequate for closed habitats environment, and do not take into account parameters specific to manned spaceflights such as environmental conditions including radiation effects and impact of microgravity on the attachment mechanisms of contaminants on modified surfaces.
In the context of future manned mission scenarios of longer duration, higher isolation and the utilization of an increasing number of closed loop life support systems, the coating or surface modification must be effective ‘in-use’.
Studies are currently being conducted to derive standard requirements for the evaluation of antimicrobial surfaces in the very specific context of manned spacecraft, but the complexity of the environment need to be derived in precise test parameters. In particular, the concentration and content of test inoculum lead to complex and hardly reproducible tests conditions, calling for in-situ data collection to support theoretical studies.
GOALS and OBJECTIVES
MATISS set of experiments aims to provide the minimum pre-required data necessary to support the development of antimicrobial surfaces for space applications and to initiate a long-term R&D project to develop and produce industrially an innovative process of surface treatment of the materials suitable for future spacecraft.
In this context, the technological demonstration MATISS-1 (Microbial Aerosol Tethering on Innovative Surfaces in the international Space Station-1) was evaluated during PROXIMA Mission by the European Astronaut Thomas Pesquet (Inc 50/51).
The objective of MATISS 1 consisted in evaluating the general operational concept and to validate the design of the MATISS payload, which protects the glass surfaces while sampling ISS atmosphere. In addition, MATISS-1 provided baseline data points of a set of variables (type of surfaces, location, duration of exposure).
MATISS-1 was a technological proof, during which we concomitantly started to evaluate four identical sample holders loaded with 5 different superhydrophobic coatings and one control applied on one substrate (glass). The sample holders were exposed at 3 different locations (EPM rack, EDR rack and RGSH) during a fixed duration (6 months).
In this respect, the characterisation of the deposits formed on the surfaces from MATISS-1 (return in the laboratory in June 2017) will establish a reference of the level and the type (dusts, biomovies) of contamination of the surfaces for a 6 months of exposure in three different zones.
MATISS-2, started in August 2018 and is foreseen to end mid of 2019. It aims to establish the kinetics of the development of the contamination on the hydrophobic/control surfaces.
MATISS-2 consisted of four identical sample holders identical to those used for MATISS-1. MATISS-2 sample holders have been installed at the same time in a single location, location chosen among the three evaluated by MATISS-1, namely the RGSH. The duration of exposure of each sample holder will be variable. In other words, the results of MATISS-1 will indicate the duration of exposure of the first sample holder of MATISS-2. The results of the first MATISS-2 sample holder downloaded will indicate the duration of exposure of the second sample holder of MATISS-2 etc.
An important specificity of MATISS-2 was that the duration of exposure was optimised with the results of the surface’s analyses done on-ground in a dynamic operational mode. Each sample holder downloaded will provide information that impact the duration of exposure of the remaining sample holders on-board.
MATISS-2.5 sets up the next step in this frame but not the last one. It will test new patterned hydrophobic surfaces in the same way we installed MATISS-2.
The interdependence between MATISS-1, MATISS-2 and MATISS-2.5 is summarised below:
MATISS-1 (tech demo): 5
MATISS-1 (tech demo): glass
Location of exposure
MATISS-1 (tech demo): 3 locations
MATISS-2: 1 location
MATISS-2.5: 1 location
Duration of exposure
MATISS-1 (tech demo): 6 months
MATISS-2.5: 6 months
Number of holders
MATISS-1 (tech demo): 4
MATISS-2 - Microbial Aerosol Tethering on Innovative Surfaces in the international space Station
ISS Increments 55-56 / 57-58 / 59-60 - 2018-2019
MATISS-1 - Microbial Aerosol Tethering on Innovative Surfaces in the international space Station (CNES
ISS Increments 49-50 / 51-52 - 2016-217
This technology demonstration was sponsored by CNES and was performed during the "Proxima" mission of Thomas Pesquet (November 2016-June 2017)
Short summary of MATISS-1
MATISS-1 consisted in uploading glass lamellas with hydrophobic and super-hydrophobic surfaces, as well as control lamellas (without coating) and in exposing them in the ISS cabin for 6 months. The surfaces were installed in a Sample Holder, which is a metallic structure designed to protect the glass surfaces while allowing ISS air to be sampled. Four sample Holders were placed in three different areas in Columbus. After 6 months, the sample holders will be downloaded and characterized on ground (expected on ground: June 2017)
The experiment consists in the following activities:
- MATISS Installation: The sample holders are installed in one predetermined locations in Columbus; The protective Kapton Tape being removed to allow air flow circulation and consist in the start of the exposure time
- MATISS Exposure: The sample holders are exposed unattended in the cabin for various durations.
- MATISS Deinstallation: The sample holders are removed one by one from their location, and protected with Kapton Tape before download
- MATISS holder surfaces will be analysed on ground to determine the remaining holders exposure duration.
MATISS Sample Holders
MATISS-2.5 uses MATISS-1/MATISS-2 sample holders already certified for flight.
The purpose of MATISS Sample Holders is to contain and protect the hydrophobic surfaces, which are the core of the MATISS-2.5 Experiment.
The sample Holder contains 1 witness surface and 5 “transformed surfaces” which have the same dimensions (glass 22 mm x 22 mm x 170 μm).
A schematic of the Sample Holder without the system of protecting lids and drawers is shown in Figure 1.
MATISS Sample Holder (FM) is depicted in Figure 2.
The surfaces are mounted in the Sample Holder, which technical drawings can be found in Figure 3 and 4.
Base: The base is made of Aluminium Au4G (2017A), is 2 mm high and acts as the structure of the Sample Holder
Plate: The Plate is made of Viton (60C7), is 1 mm high and is meant to avoid direct contact between glass/Aluminium, and to absorb vibrations during launch and return.
Kapton Tape: The Kapton Tape (0.08 mm) is glued at the back of the surfaces, to partially retain glass fragments in case of glass damage.
Seal: The seals are made of Kapton Tape to absorb vibrations during launch and return.
Grid: The Grid is made of Aluminium Au4G (2017A), is 5 mm high and protects the surfaces from impact of small objects by reducing the exposed surfaces.
Lid: The Lid is made of Polycarbonate and its height is 5 mm.The purpose of the lid is to prevent tool impact, inadvertent kick or bump during exposition in the station.
The Sample Holder is kept with Inox A2 screws (ISO 10642 / DIN 7991) M3x10, M3x8 and M3x6.
- All MATISS-2.5 sample holders shall be installed at the same time in a single pre-defined location.
- All MATISS-2.5 sample holders shall be downloaded as soon as possible pending flight opportunity after the exposure time completion (known for the first sample holder, unsettled for the three remaining sample holders)
On board: cabin temperature and humidity.
The analyses are performed on ground with the download of the four sample holders.
Two campaigns of analyses are foreseen:
The first one will be carried out exclusively with non-destructive analyses in order to bring as fast as possible a general overview of the deposits on the lamella. Three types of techniques will be possibly coupled to get such overview:
- optical microscopy inspection
- AFM microscopy
- Optical forward-scattering
The second campaign will be carried out with high resolution and possibly with destructive techniques on few selected samples. The following four types of techniques are considered:
- optical microscopy inspection
- Raman spectroscopy
- Bacterial culture
- Environmental microscopy