Invited Lecturers

Plenary Lecturers

• Dr. Tetsuro Tsuji, Graduate School of Informatics, Kyoto University, Japan

Tetsuro Tsuji received his Ph.D. degree from the Department of Mechanical Engineering and Science at Kyoto University, Japan, in 2013. After completing his Ph.D., he became an Assistant Professor at the Graduate School of Engineering Science, Osaka University. In 2019, he was appointed Assistant Professor at the Graduate School of Informatics, Kyoto University, where he has been an Associate Professor since 2021.

His current research interests include molecular fluid dynamics, rarefied gas dynamics, and microfluidics. Since the beginning of his career, he has worked on numerical analysis and theoretical modeling of non-equilibrium gaseous systems. More recently, he has also focused on microfluidic and optofluidic experiments. In particular, thermally induced microflows and microparticle motion, as well as their interconnection, are among the main topics of his recent publications.

 Title of the Plenary Lecture: Thermally-induced flows in microfluidic systems: from optothermal fluidic experiments to non-equilibrium gaseous modeling

In this talk, recent experimental and theoretical studies on thermally induced microflows will be presented.The experimental part focuses on thermophoresis, namely the motion of microparticles along a temperature gradient in fluids. Using an optothermal microfluidic system combined with optical trapping, thermally induced flows around microparticles are detected, and the relationship between these flows and thermophoresis is discussed [1].

Optothermal microfluidic systems are shown to be effective, feasible, and convenient experimental platforms for investigating thermal microflows. Based on these observations, a semi-analytical model has recently been developed [2]. In the modeling part, a kinetic model for thermally induced non-equilibrium gas flows is introduced. Despite its simplicity, the model successfully reproduces the sign reversal of thermal slip coefficients depending on gas–surface interactions [3]. These results are expected to contribute to the development of novel microfluidic functions, such as particle separation and concentration.

[1]    T. Tsuji, S. Mei, and S. Taguchi, “Thermo-osmotic slip flows around a thermophoretic microparticle characterized by optical trapping of tracers,” Physical Review Applied 20, 054061 (2023)
[2]    T. Tsuji, S. Saito, and S. Taguchi, “Semianalytical model of optothermal fluidics in a confinement,” Physical Review Fluids 9, 124202 (2024)
[3]    T. Tsuji, K. Takita, and S. Taguchi, in preparation

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• Dr. Benjamin Schafer, John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, and Rarefied Technologies, Albuquerque, NM, USA

Ben Schafer is the CEO and Co-Founder of Rarefied Technologies and an Associate Researcher at the John A. Paulson School of Engineering and Applied Sciences at Harvard University. Rarefied Technologies is a startup based in Albuquerque, New Mexico, USA, dedicated to developing photophoretic levitation technologies for near-space flight.

His research focuses on innovative designs for photophoretically flying structures, the fabrication and experimental testing of flying devices, and the application of this technology to challenges in climate science, atmospheric sensing, and telecommunications. He is a Breakthrough Energy Fellow and was recognized in Forbes 30 Under 30 as a leader in climate-focused technology. He received his PhD in Applied Physics from Harvard University in 2024.

 Title of the Plenary Lecture: Photophoretic levitation: from aerosols to aircraft

Photophoresis, or light-driven motion, of aerosols in Earth’s upper atmosphere has been studied since the 1960s. When sunlight heats an aerosol particle surrounded by rarefied gas, asymmetries in surface temperature or accommodation coefficients generate a photophoretic force, allowing the particle to levitate.

With recent advances in nanofabrication, a natural question arises: can we design engineered structures larger than aerosols, yet lightweight enough to fly autonomously? Starting from aerosol physics, this talk will review recent progress in photophoretic levitation, including holographic displays, particle traps, and macroscopic platforms for near-space flight. The potential of photophoretic aircraft for atmospheric sensing, telecommunications, and Martian exploration has motivated new research into ultra-lightweight two-dimensional materials capable of generating photophoretic gas flows.

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• Prof. Thierry Magin, Université Libre de Bruxelles, von Karman Institute for Fluid Dynamics, Belgium

Thierry Magin is a Professor at the Université Libre de Bruxelles (ULB) and the von Karman Institute for Fluid Dynamics (VKI). He obtained his PhD from ULB and VKI in 2004. Following his doctorate, he spent two years at École Centrale Paris, where he studied nonequilibrium radiation in the context of the Huygens mission. He subsequently joined Stanford University and NASA for three years, contributing to the development of aerothermodynamic models for the Orion spacecraft.

In 2010, he founded a research team at VKI with support from the European Research Council, focusing on multiscale and multiphysics modeling and computational methods for reacting and plasma flows. His research interests include hypersonics and very low Earth orbit applications. Together with his team, he investigates both fundamental physical mechanisms and aerospace technologies in collaboration with space agencies, defense organizations, and industry partners.

 Title of the Plenary Lecture: Aerothermochemistry, coupling fluid mechanics and physical chemistry to simulate aerospace flows

Modeling and simulating hypersonic flows pose major challenges, many of which stem from aerothermochemistry—a multidisciplinary field introduced by von Kármán that combines fluid mechanics, thermodynamics, and physical chemistry. Accurate modeling of gas–surface interactions, such as the ablation of thermal protection materials, is essential for predicting heat shield performance during atmospheric entry. Another important application concerns the prediction of electron densities in plasma sheaths surrounding hypersonic vehicles, which directly affect electromagnetic wave propagation.

Beyond spacecraft reentry, aerothermochemistry is also central to the study of meteor phenomena, space debris reentry, and the aerodynamics of space platforms operating in very low Earth orbit (below 150 km), where rarefied gas effects dominate. This presentation reviews the physico-chemical models and computational methods used to simulate reacting and plasma flows in aerospace applications. Particular emphasis is placed on non-equilibrium gas dynamics across both continuum and rarefied regimes, and on the coupling between chemical kinetics and fluid or kinetic equations. The talk concludes with two illustrative examples: (1) high-order CFD simulations of atmospheric entry flows accounting for thermal protection system material response; and (2) stochastic particle simulations of rarefied flows in a low-density test facility designed for air-breathing electric propulsion systems.