Sand, bacteria and a robotic arm can produce solid building parts. That is the premise behind work by Karen Antorveza Paez at ETH Zurich, who is testing whether microorganisms can act as collaborators in architecture and in the development of bacteria building materials.
Her method combines living bacteria, sand and digital fabrication. The result is a mineral structure that holds together without the heat-intensive steps used to make conventional building materials. The project is part of the department’s research into complex materials, and the questions it raises reach well beyond the lab.
Robotic dexterity is another area where ETH Zurich engineers are pushing boundaries. ETH Zurich’s five-fingered robotic hand that walks shows how machines can mimic small animal movement.
How bacteria make a mineral glue
The process is called microbiologically induced calcite precipitation, or MICP. Put simply, it is a way for bacteria to cement loose grains together, a core idea behind bacteria building materials. It is also known as biocementation.
The work relies on Sporosarcina pasteurii, a bacterium that produces an enzyme. The enzyme breaks down urea, which starts a reaction that creates calcium carbonate. That same mineral forms limestone, mussel shells and chalk.
The crystals grow between grains of sand. Over time, they lock the grains into a rigid form. Biocementation has been studied for years, mainly to stabilize loose soil and to develop self-healing concrete. Antorveza Paez treats it as a material in its own right, one that designers can shape.
Printing bacteria building materials
One of the two methods the team developed is 3D biocement printing. The bio-ink mixes sand, live bacteria and a water-based gel made from alginate and xanthan. Like conventional 3D printing, the mix is deposited in a set geometry, which is what makes these bacteria building materials printable.
After printing, each object sits in a bath of urea and calcium chloride. The bacteria drive the reaction, and the crystals slowly fill the gaps between the grains. Depending on the strength required, this takes two to five days. Fresh solution is added every day.
No furnace or kiln is involved. The material hardens at room temperature. Antorveza Paez compares the step to baking a cake, with the microorganisms serving as the oven. The team has already produced a facade element that could work as a sunshade or partition. Its final structure emerges from the printed shape and the biological activity inside it.
Robots that build up layers like rock
The second method applies biocementation directly to architectural surfaces, extending bacteria building materials into the built environment. A robotic arm lays down sand, bacteria and the chemicals needed for mineralization, one layer at a time.
The technique draws on stromatolites, sedimentary formations that microorganisms built up over long periods by depositing minerals. The team turned that geological process into an automated system. The approach appeared at the 2025 Venice Architecture Biennale in a project called Geological Microbial Formations. The robotic process ran continuously for six months, so visitors could watch the material form.
The images from the project show the difference in scale and form. Project images document the printed and robotic work. The robotic work looks different. The robotic process is documented in exhibit images.
Carbon gains and ammonium costs
Cement manufacturing is a major source of carbon emissions in construction. Bacteria building materials could offer a route that skips the high-temperature stages of conventional cement production.
For more on lower-impact construction, see eco-friendly architecture from Iran to Jaipur for other ways designers cut environmental costs.
The biological process has costs of its own. The reaction creates ammonium as a by-product. If handled poorly, ammonium can damage the environment. Antorveza Paez is now studying the environmental impact of biocementation and ways to treat this waste.
Material performance is another open question. Antorveza Paez describes biocementation as closer to mortar than concrete. Her team needs to learn how grain size, mineral bonds and internal structure affect strength and durability. Load-bearing use is a longer-term goal, not a near-term one.
Rethinking who gets to build
Architecture has long been treated as a human discipline, shaped by design, engineering and industrial production. Biocementation adds a new participant. In this model of bacteria architecture, buildings emerge from coordinated work between people, software, machines, living bacteria and minerals.
Antorveza Paez also sees the work as a way to question how architects understand their materials. Designers often know little about how the products they specify are made. Working with microorganisms makes those processes visible, and it shows how complex structures can grow from biological activity.
The project details are as follows. The work is titled 3D biocement printing and robotic biocementation spraying. The researcher is Karen Antorveza Paez. The institution is ETH Zurich, in the Department of Architecture. The research groups are Digital Building Technologies and Complex Materials Group.
This story is part of designboom’s POSTHUMAN UTOPIAS chapter, which is presented in partnership with INDX|GLOBAL, a global cultural platform that connects Indian architecture, design and creative intelligence with an international audience.
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Frequently asked questions
What is microbiologically induced calcite precipitation, or MICP?
MICP is a process in which bacteria cement loose grains together, and it is also called biocementation. The work uses Sporosarcina pasteurii, a bacterium that produces an enzyme which breaks down urea and starts a reaction creating calcium carbonate. Crystals of that mineral grow between sand grains and lock them into a rigid form.
How long does bacteria-based 3D printed material take to harden?
After printing, objects sit in a bath of urea and calcium chloride for two to five days, depending on the strength required. Fresh solution is added every day, and the material hardens at room temperature with no furnace or kiln.
What is the by-product of biocementation and why does it matter?
The biological reaction creates ammonium as a by-product. If handled poorly, ammonium can damage the environment, so the researcher is studying its environmental impact and ways to treat this waste.
What ingredients make up the bio-ink used in 3D biocement printing?
The bio-ink mixes sand, live bacteria, and a water-based gel made from alginate and xanthan. This mixture is deposited in a set geometry, like conventional 3D printing.
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