Month: October 2026

10.30.26 Dr. Mehdi Mortazavi – Worcester Polytechnic Institute – Worcester, Massachusetts

 Transport Phenomena in Proton Exchange Membrane (PEM) Fuel Cells

Date: October 30, 2026; Time: 2:30 PM Location: PWEB 175

Abstract: Hydrogen is an energy carrier that, if produced through decarbonized methods, can serve as a key solution for reducing emissions in hard-to-decarbonize industries such as long-haul trucking, cement and steel production, and aviation. Proton Exchange Membrane (PEM) fuel cells are a class of energy conversion devices that use hydrogen as fuel. Their byproducts are water and heat. Effective water management is critical for achieving durable and reliable PEM fuel cell performance. While part of the produced water helps maintain membrane hydration, excess water must be efficiently removed from the cell. The transport phenomena associated with water removal are complex and span multiple length scales ranging from a few micrometers in the pores of the porous layers to several hundred micrometers (or even millimeters, depending on design) across the flow channels. A common feature across these scales is the dominant role of capillary effects, arising from surface tension forces, which significantly influence mass and momentum transport.

This talk summarizes over a decade of research on transport phenomena in PEM fuel cells, with a primary focus on liquid water transport in different components of the cell. Particular emphasis will be placed on two-phase flow in flow channels and novel, yet simple, techniques for eliminating liquid water buildup. The presentation highlights outcomes from both experimental and theoretical investigations and briefly exemplifies how machine learning could help resolve some decades-long questions in two-phase flow pressure drop modeling.

Biographical Sketch: Mehdi Mortazavi is a faculty member in the Department of Mechanical and Materials Engineering at WPI. His research focuses on thermo-fluids systems, where he combines experimental and theoretical approaches to uncover the physics of transport phenomena in multiphase flows. He deeply values the process of discovery through collaboration with students. His current projects involve droplet dynamics, bubble actuation for enhanced hydrogen production, building energy systems, and workforce development in hydrogen energy systems. He earned his PhD in Mechanical Engineering from Michigan Technological University in 2014 and spent two years in the HVAC industry before joining Western New England University for his first academic appointment in 2016. In 2023, he joined WPI to expand his research activities through access to advanced infrastructure and graduate student mentorship.

10.16.26 Dr. Yongmin Liu – Northeastern University, Boston, USA

  Optical Metamaterials and Metasurfaces: Design, Fabrication, and Applications

Date: October 16, 2026; Time: 2:30 PM Location: PWEB 175

 

Abstract: Optical metamaterials are artificially engineered structures whose properties are primarily governed by their geometry rather than their chemical composition. By designing subwavelength building blocks—called meta-atoms—and engineering their spatial arrangement, we can realize exotic optical properties that are difficult or impossible to achieve with natural materials. Metasurfaces, the two-dimensional counterparts of metamaterials, can manipulate light on an ultrathin platform. This capability opens the door to extremely compact optical components, which could potentially replace conventional bulky lenses, waveplates, and holographic elements.

In this talk, I will begin by introducing the fundamentals of optical metamaterials [1] and metasurfaces [2], including the underlying physical mechanisms, the key principles that guide their design, and the state of the art in nanofabrication. In particular, machine learning and deep learning have emerged as powerful tools to significantly accelerate the design of sophisticated metamaterials and metasurfaces, overcoming the limitations of conventional numerical or optimization methods [3]. I will then focus on our recent work on metasurface-based applications, including high-capacity holograms [4, 5] and nanoprinting images [6], demonstrating how a single ultrathin device can encode and display rich optical information through multiple channels such as wavelength and polarization.

References: [1] Y. M. Liu and X. Zhang, Chemical Society Review 40, 2494 (2011). [2] N. Yu and F. Capasso, Nature Materials 13, 139 (2014). [3] W. Ma et al., Nature Photonics 15, 77 (2021). [4] B. Xiong et al., Science 379, 294 (2023). [5] W. Ma et al. Advanced Materials 34, 2110022 (2022). [6] L. Deng et al., Advanced Functional Materials 36, e16059 (2026).

Biographical Sketch: Dr. Yongmin Liu obtained his Ph.D. from the University of California, Berkeley in 2009. He joined the faculty of Northeastern University in Boston in Fall 2012, and currently he is currently a full professor with a joint appointment in the Department of Mechanical & Industrial Engineering and the Department of Electrical & Computer Engineering. Dr. Liu’s research interests include nano optics, nanoscale materials and engineering, plasmonics, metamaterials, biophotonics, and artificial intelligence. He has authored and co-authored more than 150 journal papers, including Science, Nature, Nature Photonics, Nature Nanotechnology, Advanced Materials, Physical Review Letters, and Nano Letters. Dr. Liu was a recipient of the Søren Buus Outstanding Research Award at Northeastern University (2024), the Faculty Fellow of College of Engineering at Northeastern University (2019), NSF CAREER Award (2017), Office of Naval Research Young Investigator Award (2016), SPIE DCS Rising Researcher Award (2016), and 3M Non-Tenured Faculty Award (2016). He has served as an associate editor or editorial board member for Nano Convergence, Nanophotonics,   PhotoniX, IEEE Journal of Selected Topics in Quantum Electronics, and EPJ Applied Metamaterials. He is a Fellow of both OPTICA (formerly OSA) and SPIE.