High-Throughput, Multiscale Testing and Evaluation of Living Cemented Materials

Microbially-induced calcite precipitation (MICP) has been recognized as an alternative to traditional cements; reversibly and quickly achieving cementation at room temperature with a lesser degree of CO₂ emissions. Low-carbon materials created using this technology may be useful for erecting impromptu structures, development of sites for humanitarian relief, or any other application requiring rapid, unintrusive ground improvement. However, improving and scaling up the biocementation process requires the development of faster-paced iterative testing devices for assessing methods production. In this study, we investigated variously scaled apparatus, which allows for gradually upscaled testing and increasing resolution with respect to evaluation of materials. These devices generally take the form of walled openings with a liquid-permeable mesh in the lower portion, allowing percolation of bacterial suspension solutions and cementation solutions. To increase throughput of experimentation, we used a pipetting robot to apply solutions between 176 microliter to 8 milliliter scale. This allowed for various methods and solutions to be tested simultaneously with numerous replicates. Experimental manipulation included the growth environment of the bacteria, growth media, and soil conditions. Using this process, it is possible to alter formulations to target specific traits and features of biocement. In our results, we found that strength is largely proportional to the amount of Ca²⁺ administered to the system, in addition to preconditions such as urea availability during growth, growth media type, and soil moisture content. Some conditions thought to not be viable for cementation are now considered viable, such as bacterial cultures grown without urea. Not only is this method viable, but it has comparable strength values to the average 60-80 PSI (unconfined compressive strength, UCS) achieved with conditions considered average per our results with a standard treatment. Using these methods, our standard treatment has improved by 160% from an average of 50 PSI to an average of 80 PSI, with strengths of 300 PSI being recorded outside of standard conditions. Our automated method allows testing of high-impact questions at a low-stakes opportunity cost by removing the restrictions imposed by time and material commitment.