This article is taken from Science et Avenir – La recherche n ° 899, dated January 2022.

The building is not equipped with any ventilation system, yet it “breathes”. Its skin-like walls have invisible gaps that regulate the ambient temperature and humidity. They open when they exceed a certain threshold, allowing air to circulate through the walls. And when the outside is too wet, the pores get clogged, leaving the inside dry. Without any energy sources or greenhouse gas emissions!

Homes like this could see daylight in just a few years, thanks to a new type of material developed by Hub for Biotechnology in the Built Environment, a collaboration between researchers from the University of Newcastle and the University of Northumbria (United Kingdom). baptism”Respiratory: Passive, responsive, variable porosity building skins“His project has just received the first private funding of €400,000. “It involves ingesting the spores of a microbe – the bacterium. Bacillus subtilisS – between inert layers of latex “These spores, which are about a micrometer (one-thousandth of a millimeter) in diameter, shrink or expand depending on the level of moisture,” says team member Ben Bridgens. Thus they behave like pistons that spin on their own. One and a half times the mass of the can, resulting in smaller pores. Trials are underway to integrate the device into the building material. And prototypes will be presented to the public “until next year” , assured the British scientist.

“Projecting life into inert structures”

These breathable walls are just one of many applications envisioned for a new family of materials called “living engineering materials” or more simply “living materials”. “The general idea is to introduce life into inert structures such as polymers, concrete or glass. Living organisms can be bacteria or fungi, but so can plant and even animal cells. “, points to Bao-Lian Su, a chemist at the University of Namur (Belgium) and a member of the European Academy of Sciences, who introduced the name in the mid-2000s.

“Cells Aren’t Equal Contains inactive part. They influence the development and intimate architecture of the final products, which gives them unprecedented properties based on the main functions of living things. “, emphasizes Matthew Etienne, researcher in Physical Chemistry and Microbiology for Materials and the Environment at Nancy (Meurth-et-Moselle). These artificial hybrid materials can thus produce a self-organizing, self-repairing, agglomeration of molecules. , or even react to changes in their environment, as in the aspects developed at the University of Newcastle.

“Today, the funding is coming in and the sector is exploding “, appeases Bao-Lian Su. As evidenced, scientific publications have increased tenfold between 2017 and 2021, from a small thirty to more than 300. “This acceleration can be explained by recent and tremendous advances in synthetic biology, which manipulate the genomes of cells and give them desired properties. But, also, by an increasingly close collaboration between biologists and experts in materials science “, analyzes American Will Sarber.

Specializing in structural engineering, in 2015 he created the Laboratory for Living Materials at the University of Colorado at Boulder (United States). And has since raised about $13 million for various research projects. In early 2020, his team, under the auspices of the US Army, thus designed a type of mortar capable of self-replication. It is composed of cyanobacteria (genus. K) sinechocokus) which secretes calcium carbonate, the basic ingredient in cement. These microorganisms have been mixed with nutrients, gelatin and sand. While gelatin serves as a support for bacterial growth, calcium carbonate minerals the whole which gradually hardens. Result: In just half a dozen hours, we’ve got concrete-resistant bricks! Then split only one of them and pour gelatin and sand into a mold so that bacterial growth resumes and produces two new bricks, these can then be divided to make four, eight, sixteen, etc. A start-up (Prometheus Materials) has already been formed to develop this technology. And a pilot plant is expected to be built by the end of 2022.

US military builds on sand

The DARPA, the US military’s Agency for Advanced Research Projects, has a keen interest in engineering living materials. In 2016, it launchedEngineer Living Materials Program who listens “Revolutionizing logistics and military construction in remote, harsh, high-risk environments or affected by natural disasters “,” explains Blake Bextine, who is spearheading the program. Among the research that DARPA funded, bricks that rapidly self-replicate are made from cyanobacteria and developed at the University of Colorado. “Almost mature this technology should benefit both the military and the private sector. “, specifies the biologist. This will make it possible to build barracks in distant theaters. “Without transporting tons of material, because they will ‘grow’ straight on site. Another example with the Medusa Project, in reference to the mythical monster that turned its victims to stone. This involves creating momentary landing strips by soaking bacteria and nutrients onto the sand that hardens the whole thing very strongly (see l (illustration in this article)) The process was successfully tested on the island of Guam (Pacific Ocean) in July 2021 This allowed the landing of helicopters and CV-22 tiltrotor aircraft.

Microscopic algae make medicine round the clock

Evidence that the branch is being structured, the First International Congress (entitled living material) was held in Saarbrücken (Germany) in February 2020. “Very multidisciplinary, it brought together over 120 microbiologists, chemists, physicists and engineers as well as industrialists, even though Asians were unable to participate due to the coronavirus pandemic, Bao-Lian Su’s report, We felt a strong enthusiasm, a very strong need to share new achievements. ,

Namur scientist presented on this occasion algae factory, the European project that it coordinates. It takes advantage of the photosynthetic properties of marine microalgae (eg Dunaliella) – which produce organic molecules in the presence of water, light and carbon dioxide – to create … pharmaceutical factories! Microalgae are contained in a porous matrix of silica and alginates, biocompatible and very malleable polymers. Installed in a photobioreactor, the resulting hydrogel thus forms, 24 hours a day, various pharmaceutical products with high added value, such as antioxidant, antibiotic or anticancer molecules. “The process should mature within five to six years “, Esteem Bao-Lian Su.

Also present in Saarbrücken, Mathieu Etienne details other potential applications in the renewable energy and environmental sectors. His team uses different bacteria like shewanella oneidensis whose metabolism expels negative electric charges (electrons). By embedding these microbes into a network of carbon nanotubes (which capture and transport electrons), she forms electro-active bio-films with attractive properties. Accumulating in polluted environments, they destroy nitrates of agricultural origin due to chemical oxidation-reduction reactions. Applied to food waste, they break down organic matter and produce bio-hydrogen which is used to power the batteries themselves.

Though there is no dearth of outlets, there are many challenges that need to be overcome to move ahead at the industrial level. to start with Long-term viability and maintenance of cells“, Will Sarber says. “Nos Microalgae” barely live more than a year, Bao-Lian recognizes Suu, Not to mention that their effectiveness rapidly declines over time. “To improve the living conditions of cells, researchers focus specifically on the structures that surround them and protect them from external conditions: they should not be too thick, otherwise the organisms will fall apart and die. The overall architecture also plays a decisive role, as they tend to be neither too fragile, as they then dissolve quickly. “We must identify and optimize networks that allow good communication between cells, the transport of nutrients, and the elimination of waste products from metabolism, Bao-Lian Sue specifies, In the form of bone structures, coral or tree leaves, moreover, natural living material which is our best source of inspiration. ,

Click on picture to enlarge. credit: Bruno Bourgeois

Ethical and Biosafety Questions

Living material raises important social issues. “Whether they are of bacterial, plant or animal origin, most of the organisms involved in this type of material have been profoundly modified., underlines chemist Mathieu Etienne in Nancy. It should therefore be considered by ethics committees and legislators to determine which researches and applications can or cannot be made and generalized.” Standards also have to be established to guarantee their absolute harmlessness. “We are very attentive to the ethical and legal implications, especially the impact on the environment if these organisms are to be used in daily life”, explains Blake Bextine, a biologist working for the US military.