CAREER: Transforming Multiphase Flow in Porous Media from Passive Pore Fluids to Active Suspensions of Motile Bacteria

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

This Faculty Early Career Development (CAREER) grant will promote the scientific understanding of active particles at gas-liquid-mineral interfaces and use the insights gained to shift the paradigm in adaptive control of multiphase flow in porous media. Multiphase flow in porous media is mainly governed by the rheological properties of pore fluids and the gas-fluid-mineral interactions. These processes can be substantially altered by adding active suspensions, which are self-propelling objects that can inject energy, generate mechanical stress, or create flows within fluids. Active particles are revolutionizing many industrial and scientific fields, such as ferromagnetic particles for dynamic sealing, micro-robots for targeted delivery of drugs, molecular motors to facilitate cell locomotion, and motile bacteria to tune water into superfluids. Studying active fluids in porous media can renovate commercial techniques in geosystems infrastructure and subsurface energy that will increase the economic and technological competitiveness of the United States. Particularly, translating the technology of using active suspensions into the practical improvement of resource recovery and reliable waste disposal can transform and benefit society. Knowledge gained from this award can also provide insights into microbial infection, bio-microrobots design, and targeted delivery that are relevant to many environmental and health issues pertaining to the well-being of individuals in society. Research and education activities of this CAREER grant will be integrated to foster a cross-disciplinary community in energy geotechnics, inspire the interests of diverse student groups in geotechnics and STEM subjects, and broaden dissemination to the public of the critical role of geotechnical engineering in addressing global challenges related to sustainability and energy. This grant will also facilitate long-term mentoring relationships between the PI and participants, which will strengthen and diversify the underrepresented minority STEM pipeline. The research objective of this CAREER grant is to understand and model the interactions between motile bacteria and gas-liquid-mineral interfaces. Combined experimental, numerical and analytical modeling will be performed to investigate the effects of three strains of Escherichia coli with different motility (1) at the gas-liquid interface, (2) in pendant and sessile droplets, (3) as bacteria-laden interface migrating through pore space, and (4) during wetting and drying processes in porous media. This research will ultimate (1) quantify the gas-liquid interfacial tension with suspended active particles, (2) understand the role of motility on the hydrodynamic dispersion of bacteria in a pendant droplet, (3) evaluate bacteria motility to pin or depin sessile droplets on hydrophobic and hydrophilic mineral surfaces, (4) measure the capillary signature as active-particle-laden interfaces migrating through pore throats, and (5) model the macroscopic spreading dynamics of motile and nonmotile Escherichia coli during the wetting and drying processes in porous media. Active pore fluids are non-equilibrium systems, present novel features that are interesting scientifically in their own rights. This grant supports the fundamental understanding of the non-linear behavior of active-particle-laden interfaces, which exhibit unique capillarity signatures and buckling mechanisms as they migrate through irregular pore spaces. Research findings of how microbial motility alters multiphase flow patterns provide innovative approaches to subsurface flow management, enhanced resource recovery, adaptive control and targeted delivery of fluids (and associated heat, nutrients, and mass) transfer in porous media. The new knowledge and techniques obtained through this project can be used to develop disruptive technologies of using man-made active particles to alter many fundamental soil phenomena, such as seepage, drainage, consolidation, and liquefaction. Integrated educational objectives of this CAREER grant are to engage a cross-disciplinary community in energy geotechnics and generate greater awareness amongst the public about the geotechnical role in addressing global challenges related to sustainable and energy-viable society. To achieve these objectives, a Vertically Integrated Program on subsurface energy involving K-12 STEM students (through the Research, Experiment, Analyze, Learn REAL program), undergraduate and graduate research assistants, and high school teachers (through the Georgia Intern Fellowship for Teacher GIFT program) will be established to engage a cross-disciplinary community in active fluids through porous media. The research and educational outcomes will be disseminated through increasing scientific literacy, designing classroom challenge problems related to subsurface flow for Atlanta K-12 schools and summer camps, and developing a mobile app that students and public users can select different natural or man-made porous materials to visualize the flow of various fluids and the impacts of added active particles. These products will also be presented at the Tellus Science Museum, Atlanta Science Festival, and Energy Expo. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.