(4dy) Physicochemical Fluid Dynamics for Energy and the Environment

Fluids are pervasive throughout nature, critically mediating many transport processes that are key to the environment and the ongoing energy transition. Engineering these processes into applications depends on the description of not only the flow mechanics, but also the physical chemistry of the fluid constituents at small scales, which is often poorly understood. Through a combination of theory and experiments, I seek to bridge this knowledge gap by (i) identifying the core physicochemical mechanisms behind out-of-equilibrium processes observed in nature, and (ii) developing mathematical models for their description from first principles. My research mission is to achieve a fundamental understanding of transport phenomena underlying practical applications in energy and the environment, working at the intersection of fluid dynamics and physical chemistry. The insights gained will be directed towards advancing the next generation of sustainability technology, including more efficient soil and water remediation or new methods for the extraction of minerals crucial for decarbonization.

Research Experience:

During my PhD at UC Santa Barbara, I studied the dynamics of surfactants at fluid interfaces and their effect on coatings aimed at reducing hydrodynamic drag, using a combination of theory and experiments with Paolo Luzzatto-Fegiz and computational approaches with Frédéric Gibou. I then moved to Princeton University as a Distinguished Postdoctoral Fellow at the Andlinger Center for Energy and the Environment. Working with Howard Stone, I am focusing on environmental problems broadly characterized by the presence of colloids and phase change, in collaboration with the groups of Jason Ren and Sujit Datta. My main research contributions to date can be classified as follows:

1. Evaporation-driven flows of electrolytes: I developed theoretical models of salt concentration driven by evaporative flows, resulting in a significant improvement over standard techniques for lithium separation from brines. Using microfluidics, I have also designed and built a lab-scale platform to probe the fundamental physical mechanisms that mediate electrolyte evaporation, gaining insights towards practical applications including mineral extraction, remediation of heavy metals, and recycling of industrial wastewater.

2. Surfactant dynamics at fluid interfaces: Through confocal microscopy experiments and mathematical modeling, I established the first quantitative understanding of how surfactants affect friction-reducing superhydrophobic textures, relevant for energy efficiency in industries like maritime transportation. I also contributed fundamental insights on spreading via Marangoni flows, namely (i) the discovery of maze-solving behavior of surfactants in complex networks, and (ii) the mathematical formulation of Marangoni spreading at low Reynolds number.

3. Bacterial and colloidal suspensions: I derived the theoretical maximum efficiency of water filtration using diffusiophoresis (i.e., the migration of suspended solids triggered by chemical gradients), and verified it using microfluidic experiments. This paves the way towards alternative methods of water remediation for sub-millimeter solids like microplastics and nanoplastics, which are expensive to remove with traditional physical filters. Furthermore, I have produced a model quantifying the coupling between chemotactic bacteria and the dissolution of chemo-attractant droplets, relevant to quantifying and designing novel approaches to soil bioremediation.

Research Vision:

Building upon a strong foundation in applied mathematics and fluid flow experiments, my research group will study transport processes in emerging environmental and energy applications with potentially high societal impact. The open questions we will explore can broadly be classified as:

1. Chemically-driven interfacial transport: The interplay between chemical kinetics and interfacial processes like phase change or electrostatic interactions is at the heart of many fluid flows at small scales. Crucially, reactions are inherently present in multiple industrial and natural settings, and their potential to induce fluid flows, which is often neglected, opens a new realm of possibilities to exploit chemistry in practical applications. For example, can industrially important chemical reactions be leveraged to induce the separation of solids through diffusiophoresis as a by-product, leading to efficient methods for wastewater filtration? How can the interplay between the dissolution of pollutants and bacterial chemotaxis be tuned to enhance the rate of bioremediation at a population scale?

2. Out-of-equilibrium mass transfer in disordered media: Elucidating the physicochemical mechanisms behind transport in porous materials is challenging due to their multiscale nature and the difficulty of flow visualization, often leading to quantitative descriptions limited to thermodynamic equilibrium. However, porous materials in nature commonly contain concentration gradients, colloidal particles (microplastics, insoluble liquid pollutants), and are driven by processes like evaporation. What is the role of out-of-equilibrium mechanisms like diffusiophoresis or Marangoni flows in the transport of contaminants across aquifers in the environment? How can we leverage these coupled processes to harness evaporative mineral extraction from natural brines at industrial scales?

3. Effective description of transport across scales: Central to the quantitative description of physical phenomena is the derivation of large-scale effective theories from the detailed small-scale interactions between the system constituents. In the case of multiphase flows, this upscaling is challenging due to the nonlinear interactions involving reaction kinetics, phase change, or interfacial stresses at small scales. Using theoretical methods like the renormalization group, can we, for instance, build effective theories for mass transport in electrolytes in the presence of complex reaction kinetics between ions? Can we gain new insights about mixing processes of complex fluids relevant for the environment, like surfactants or particle suspensions?

Teaching Interests:

I strive to make a meaningful contribution to the academic community through teaching, and have consistently sought opportunities to reinforce my pedagogy. As a graduate student at UC Santa Barbara, I received six teaching assistant appointments for undergraduate courses in thermodynamics, heat transfer, fluid mechanics, and numerical methods. At Princeton, I was the main instructor of a multivariable calculus course (EGR 156) with 80 enrolled undergraduates throughout the Fall semester of 2022. My roles included lecturing, the coordination of four teaching assistants, and the design of coursework, problem sets, and exams.

Building upon this background, I continuously cultivate a teaching style centered around student engagement. I plan to make extensive use of new visualization tools to create three-dimensional, time-evolving graphics that supplement traditional lectures confined to a static blackboard. My experience building in-class demos to illustrate concepts like the Marangoni effect (bit.ly/flowmaze) will also be key towards my main goal of making fundamental concepts accessible to all students. My technical expertise enables me to teach any class on transport phenomena, thermodynamics or applied mathematics in an undergraduate or graduate curriculum in Chemical Engineering. I am particularly interested in designing a graduate course focusing on interfacial transport phenomena, covering topics from capillarity and surfactants to dissolution and phase separation.

Honors and Awards:

1. Exemplar Mentor Award, McGraw Center for Teaching and Learning, Princeton University (2024).

2. Rising Stars in Mechanical Engineering, UC Berkeley (2023).

3. Distinguished Postdoctoral Fellowship, Andlinger Center for Energy and the Environment, Princeton University (2021-2023).

4. Best PhD Dissertation in Mechanical Engineering, UC Santa Barbara (2021).

5. WAGS/ProQuest Distinguished Master’s Thesis Award, STEM category (2019).

6. First place in the Mechanical Engineering Grad Slam Competition, UC Santa Barbara (2018)

7. Gallery of Fluid Motion Award, APS Division of Fluid Dynamics (2017).

Selected Publications:

1. F. Temprano-Coleto, H.A. Stone, “On the self-similarity of unbounded viscous Marangoni flows”, submitted. Preprint at arXiv:2401.13647 (2024).

2. F. Temprano-Coleto, S.M. Smith, F.J. Peaudecerf, J.R. Landel, F. Gibou, P. Luzzatto-Fegiz, “A single parameter can predict surfactant impairment of superhydrophobic drag reduction”, Proceedings of the National Academy of Sciences 120 (3) e2211092120 (2023).

3. X. Chen, M. Yang, S. Zheng, F. Temprano-Coleto, Q. Dong, G. Cheng, N. Yao, H.A. Stone, L. Hu, Z.J. Ren, “Spatially separated crystallization for selective lithium extraction from saline water”, Nature Water 1, 808–817 (2023).