Crystal Growth of MICP through Microfluidic Chip Tests

A significant pressing issue in microbially induced calcium carbonate precipitation (MICP) is the characterization of the heterogeneous growth mechanics of calcium carbonate (CaCO3) crystals. This study aimed to visualize the bacteria and CaCO3 distributions at the quiescent state through microfluidic chip tests where the bacterial solution (BS) and cementation solution (CS) were initially injected simultaneously from two separate microchannels and subsequently converged in a reaction microchannel. The experiments revealed that the bacterial diffusion within the CS injection area was hindered for a high concentration of calcium chloride (CaCl2) (e.g., 0.5 M), whereas diffusion appeared homogeneous for a low concentration of CaCl2 (0.05 M). In addition, the CaCO3 distribution along the width of the reaction microchannel was more uniform for 0.05 M CaCl2 than for 0.5 M CaCl2. The microfluidic chip tests in this study provided kinetic observations of the MICP process that improved the understanding of the mechanics of bacterial diffusion and CaCO3 crystal growth and their variation with different concentrations of CaCl2.