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Engineered yeast glue turns sand into 3D-printable 'living cement' aimed at Mars
Chinese researchers made a 3D-printable 'living cement' from engineered yeast, gelatin and sand that reached 12 MPa of compressive strength. So far, its promise of Mars shelters printed from local dirt rests on tests with sand and on gelatin that would have to be launched from Earth.
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What happened
- The binder comes from a Saccharomyces cerevisiae yeast strain engineered to make adhesive proteins, one of them similar to the protein mussels use to stick to rock.
- Gelatin forms a hydrogel around the mix, producing an initially gloopy paste that can be extruded through 3D-printer nozzles into complex shapes.
- On Mars the print would cure by freeze-drying, as water freezes and sublimates to leave a porous network of gelatin, yeast protein and mineral grains.
- With 6 MPa of flexural strength, the material is roughly on par with low-strength, lightweight concrete on Earth, according to Interesting Engineering.
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Why it matters
- cost Every wall printed with the current recipe needs regular deliveries from Earth, because the gelatin has to keep arriving until a fully biological binder is as strong as the gelatin version.
- exposure A habitat design that counted on the lab strength figures would be relying on sand data, and a mix with perchlorates and real regolith grains has yet to be run.
- decision Planners would still source and launch a pressure membrane separately, so the printed cement competes for the shell and shielding budget instead of replacing the pressure hull.
Anyone who signs the cargo manifest for a Mars base would read this research for one line: what still has to be launched. Interesting Engineering's account of the work says that, in theory, the answer is the biological starter material, some processing equipment and a large robot printer [8]. Local soil or regolith makes up most of the material [15].
The caveats in the same report put two more items back on that list. The gelatin comes from pigs and would need to be shipped in [11]. Pressurized structures are still an open problem. The team proposes a ready-made pressure-retaining membrane, enclosed by a shell and shielding built from the new material [13]. That takes the launch list from three items to five [1].
The team did try leaving the pig out. A gelatin-free version performed worse, and the researchers say stronger fully biological binders will be needed [12]. The report calls the process relatively cheap but does not put a figure on it [2].
The soil is the bigger gap. The tested material used sand in place of Martian regolith [10]. Real regolith has different particle characteristics and contains perchlorates, and nobody has yet tested how the gelatin-yeast mix reacts to them [10]. The cure also depends on the site. The team chose to work with Mars's thin atmosphere and an average temperature of about -53C instead of fighting them [14][5].
For now the result is for materials researchers and mission architects. The report's promise of shelters comes with its own condition: "if able to scale" [2].
I'd test this, and any claim about building from local dirt, with a two-by-two for each input. One axis asks whether the input comes from the site or from Earth. The other asks whether it was tested in the form it would take on site. The gelatin and the yeast starter are tested but shipped [11][8]. The membrane is shipped and so far only proposed [13]. The soil is local and untested, because sand stood in for it [10]. An input comes off the manifest only when it reaches the local-and-tested box, and none has yet.
In my view the right label for this is a binder result, and the habitat claim should wait until the soil moves boxes. The tradeoff is that the parts of the recipe already tested are the shipped ones. That means the wait falls on the input that makes up most of every wall [15].
What to watch
- Results from the yeast-gelatin mix made with real or simulated Martian regolith containing perchlorates.
- A fully biological binder that matches the gelatin formulation's strength, taking pig gelatin off the shipping list.
- A cost figure or a printed structure beyond lab samples, the first evidence on the report's 'if able to scale' condition.