Research directions
Microfluidics
Boreholes drilled into the ground represent traditionally the main source of information about subsurface processes and phenomena, due to the opaque nature of soil and rocks. We build two dimensional micro-models analogs of simplified confined media that consist in two parallel (at least one transparent) solid layers separated by a thin gap filled with impermeable solid obstacles, whose size and shape are designed at will using photo-lithography in a range between micrometers to millimeters.
Microbial transport & chemotaxis
Many soil-dwelling microbes respond to chemical gradients collectively migrating along the gradients direction. This behaviour will affect the microbes residence time and transport properties when exposed to heterogeneous pore-scale flows: it results in a increase in their ability to retain position within pore-scale (few microns) chemical hot-spots, increasing the longitudinal dispersion coefficient. Thus, the small scale flows heterogeneity will also likely control the bio-geo-chemical processes that microbes mediate.
Horizontal Gene Transfer in confined micro-structures
Soil microbial communities are exposed to transported portions of DNA, Mobile Genetic Elements (MGE), which in case of environmental stress can be incorporated by the microbes with a consequent appearance of new physiological functions. The mechanisms responsible for such (horizontal) gene transfer are controlled by the environmental conditions. Thus, due to the complexity of small scale confined flow, the predictions based on rates, measured in well-mixed batch reactors, may differ by orders of magnitudes from observations in the field.
Mixing in confined flows
Despite the low Reynolds number characterising porous media flows, transport and mixing of solutes and microbes suspensions in confined environments is non trivial. While some mixing properties are shared with turbulent and chaotic systems, there are fundamental differences that must be taken into account to properly model and predict the dynamics of mixing in such media, including the presence of solid boundaries, no flow zones and different flow kinetics and distributions.
Displacing reactive fronts
Only when mixed (occupying the same volume), different chemicals and/or microbes can interact and transform: the mixing dynamics resulting from the combined action of diffusion, dispersion, and advective stretching of a reaction front in heterogeneous flows leads to kinetics that can differ by orders of magnitude from those measured in well-mixed batch reactors. For instance, the reactive front invading a confined medium develop a filamentary structure that elongates and eventually coalesce, controlling the overall reaction kinetics.
