Poster Y8 - MICROFLUIDIC AND COMPUTATIONAL APPROACH TO MODELING BIOMINERALIZATION IN LIVING MATERIALS

Introduction: Sporosarcina Pasteurii is an optimal biomineralizing organism that can effectively decrease hydraulic conductivity by binding porous materials together [1]. Ureolytic bacteria are a favorable solution to environmental remediation, forming bio-cement in small spaces where other binding materials cannot reach. In the presence of urea and calcium, these bacteria produce microbial induced calcium carbonate precipitation (MICP). While MICP has been combined with cement to repair cracks [2], we are the first to combine it with hempcrete, a recent carbon neutral building material. This carbon sequestering living material could provide a far more advantageous replacement of resource demanding building materials like cement and insulation. Additionally, future aims include genetically modifying existing bacterial strains for mechanically induced MICP, providing increased calcification in areas requiring greater structural integrity. Here, we demonstrate a microfluidic approach to understand the bacterial microenvironment and build our computational modeling. Both a microfluidic and computational approach will aide in the understanding of self-repairing living materials, starting with biomineralizing hempcrete.

Materials and

Methods: We first start by a 3D printing our microfluidic PDMS molds using fast curing resin. This method has enabled fast and low-cost prototyping, allowing us to try many designs to replicate porous structures. Each mold takes about 18 hours to manufacture and the cost of goods is $12 per mold. Once the microfluidic devices are fabricated, the bacterial solution containing S. Pasteurii is inoculated into the device, followed by 24 hours of cement solution containing reagents required for MICP (Figure 2). The auto-fluorescent of the calcium carbonate crystals was captured with an inverted fluorescent microscope, showing precipitation growth over time (Figure 3). These time-lapse images show real-time biomineralizing connections between pores, allowing exploration of load bearing actuation on the chip, which will be used to test the genetically modified bacteria soon.

Results, Conclusions, and Discussions: In parallel with image acquisition, we are acquiring batch reaction kinetics from bench top flask studies as well as the effluent samples from the microfluidic devices. Urea, ammonium, soluble calcium, pH, and calcium carbonate precipitate are measured over time to calculate precipitation kinetics, aiding in the development of our computational model. We have developed a novel agent-based model for biomineralization that incorporates biofilm growth, urease secretion, chemicals diffusion, and calcium carbonate precipitation (Figure 4). Additionally, we will be adding hemp hurd into the PDMS casting process to explore direct precipitation of the final material. With these preliminary results, we are excited to numerically simulate the complexities of self-healing living materials to fortify hempcrete, as well as other developing materials that promote sustainability.

Acknowledgements (Optional): 1. Heveran, Chelsea M., et al. “Biomineralization and successive regeneration of engineered living building materials.” Matter, vol. 2, no. 2, Feb. 2020, pp. 481–94
2. Nasser, Amal A., et al. “Microbially-Induced-Calcite-Precipitation (MICP): A Biotechnological Approach to Enhance the Durability of Concrete Using Bacillus Pasteurii and Bacillus Sphaericus.” Heliyon, vol. 8, no. 7, July 2022, p. e09879