Chip allows scientists to study bio-cement formation in real time
Scientists from EPFL and the University of Lausanne used a chip originally designed for environmental science to study the properties of bio-cement formation. This material has the potential to replace traditional cementitious adhesives in a number of civil engineering applications.
The chip is about the size of a credit card, and its surface is etched with a one-meter flow channel from end to end, as thick as a human hair. The researchers were able to introduce a solution to one end of the channel and, with the help of a time-lapse microscope, observe the behavior of the solution for several hours. Medical scientists have used similar chips for healthcare applications, such as to check how clogged arteries or how a drug spreads into the bloodstream, while engineers Environmentalists have applied them to study biofilms and contaminants in drinking water.
Now, a team of civil engineers at EPFL’s Soil Mechanics Laboratory (LMS), along with scientists from the Department of Geosciences and Environmental Sciences at the University of Lausanne (UNIL), have reused chip to understand the complex transport-reaction phenomena involved in the formation of new bio-cements.
Ariadni Elmaloglou, Ph.D. the student, along with Dimitrios Terzis, one of her thesis instructors from EPFL’s Laboratory of Soil Mechanics (LMS), injected bio-cement solutions into microfluidic chips that resemble sands vary to see how the minerals form and the flow reacts. Besides the sands, the other major bio-cement components—calcium and urea—remain the same.
“Thanks to the chip, we were able to observe variations in the mass distribution of biocement in different blends,” says Elmaloglou. “For example, we can see where minerals are formed and what mixtures can lead to superior mechanical properties over long flow paths. Due to its miniaturized mass, the chip allows we perform many experiments with different mixtures to design effective bio-cement protocols.”
Test meters long
The engineers’ findings have just been published in the journal Scientific reports. Their study is the first to examine bio-cement formation over a meter length in real time, which is important for many potential applications such as crack repair, carbon storage and soil improvement. All data has been made available in an open source format to encourage further research on this topic.
Meanwhile, the LMS engineers have begun their next research step. “The Chips “It makes it easy for us to test bio-cement made from aggregates of recycled materials—like glass, plastic or crushed concrete—rather than sand,” says Terzis.
“The industry is still heavily reliant on concrete, although the ingredients used to make it – especially sand – are increasingly difficult to source. Our research shows that a An interdisciplinary approach can help change that in the long run. But we need to be open to methods from other areas of research.”
Inventing new types of bio-cement at EPFL
For his doctoral degree. PhD thesis at LMS, Dimitrios Terzis has developed a new bio-cement made with bacteria and urea. This process involves the use of calcium carbonate (CaCO3) crystals to bind soil particles together, instead of cement clinker. The result is a bio-based material that is easy to use, durable and relatively low cost compared to existing binders, including cement, lime and industrial resins. In particular, plastics can become relatively unstable over long periods of time, can contaminate soils with microplastics or toxic compounds, and can increase groundwater alkalinity to levels beyond limits. allow.
The bio-cement developed by EPFL can be cheaply produced on site and ambient temperature, with only a small amount of electricity needed. Operators can tailor bio-cement levels to their specific needs. If only a small amount of CaCO3 added, the operator obtains sandstone-like results that are strong enough to withstand seismic shear stresses that can lead to soil liquefaction.
Other applications can help with slope stabilization or restore existing foundations. If a lot of CaCO3 Biominerals are added, the result is a mixture that can be used as a building material or as a waterproofing soil.
To bring their technology to market, Terzis and Professor Lyesse Laloui founded MeduSoil, an EPFL startup, in 2018. The company has conducted field demonstrations in Switzerland and abroad.
Ariadni Elmaloglou et al, Studying microfluidication in a one meter long reaction pathway reveals how the structural heterogeneity of the medium forms the bioadhesion process induced by MICP, Scientific reports (2022). DOI: 10.1038/s41598-022-24124-6
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Ecole Polytechnique Federale de Lausanne
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