Colloidal Behavior of Carbonate Particles Microbially Precipitated in Microfluidic Droplets.

Microbially Induced Calcium Carbonate Precipitation (MICP) is an environmentally friendly biotechnology used to consolidate materials and soils at room temperature. While the bacterial enzymatic reaction underlying MICP and its application at large scale have been extensively researched, less is known about the colloidal interactions and potential aggregation of the calcium carbonate particles precipitated through this process. In this work, we study the composition, structure, and dynamics of the colloidal aggregates formed in mineralizing MICP solutions. To enable real-time visualization and full control over the mineralization process, the bacteria-driven assembly of colloidal particles is investigated inside microfluidic droplets. Brightfield microscopy, confocal scanning laser microscopy, and Raman spectroscopy revealed that bacterial cells and calcium carbonate particles co-assemble into open, fractal networks during the biomineralization process. Such findings indicate that a simple colloidal aggregation process governs the assembly of microbially precipitated particles in complex MICP media.