Seminars

Dr. Lynn Katz

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Host: Prof. Vinh Nguyen

Columbus Day No Seminar

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Prof. Shiwang Cheng
Michigan State University

"TBD"

Host: Prof. Shengfeng Cheng

No Seminar (Thanksgiving Break)

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Binghan Liu Virginia Tech

“Physical Mechanism and Control of Stratification in Drying Films of Colloidal Mixtures”

Stratification is an interesting and potentially useful non-equilibrium phenomenon that occurs in a film containing mixtures of colloids and polymers when it is rapidly dried. It is the outcome of complex interplay between a range of processes including evaporation, diffusion, absorption, phoresies, and osmosis that take place at the liquid-vapor interface, in the bulk of the film, and at the surface of the substrate. This dissertation employs large-scale molecular dynamics simulations to reveal the physical mechanisms driving stratification in drying films of polydisperse colloidal mixtures, based on the concept of Diffusiophoresis, where a colloidal particle migrates in response to the concentration gradient of other types of solute particles in the suspension. The results support the notion that the asymmetric diffusiophoretic response of small and large particles plays a key role in yielding a stratified colloidal film after rapid solvent evaporation. Further simulations show that the shape of particles can also influence their diffusiophoretic behavior. Therefore, stratification can occur in drying films containing particles with various shapes. Next, the dissertation demonstrates that a binary mixture of solvents possessing different volatilities can be used to drive a binary blend of colloidal articles of the same size to stratify through contrasting couplings between the particle and the solvent components. Finally, the dissertation explores the drying behavior of colloidal films in two dimensions and the results are compared with those in there dimensions. The results in this dissertation offer new insights into the physical mechanisms and control strategies of stratification in drying films of colloidal mixtures.

Host: Shengfeng Cheng

Prof. Pham Thang Virginia Tech, Material Engineering

“Nanostructured Quantum Materials: From Deterministic Synthesis to Multimodal Characterization”

Development of qubits in recent years has been underlined by advances through circuit design, device fabrication, and standardized metrology to systematically compare qubit performance created by different platforms. However, further improvement and especially, scalable manufacturing of qubits require a bottom-up approach in which one can control the assembly and interaction of atoms across different interfaces. This quest calls for advances in materials synthesis, characterization, processing, in addition to materials selection. In my talk, I will identify problems in quantum information science (QIS) which materials science and engineering can uniquely address. First, I will show my recent results in understanding the coherence-structure relationship in superconducting materials and qubits using multimodal electron microscopy. In the second part, I will discuss my efforts in designing a new quantum material platform, namely one-dimensional van der Waals materials with controlled morphology, chemistry and interface. Finally, I will introduce my research group at VT and how we are planning to develop data-driven materials synthesis and characterization for applications in QIS.

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Special Time and Datea

Chinmay Katke Virginia Tech

"Chemically Driven Soft Bioinspired Materials-4 Billion Years Apart"

Intermolecular forces play a crucial role in driving the response of living organisms to environmental stimuli. To design and engineer soft bioinspired materials for applications such as drug delivery and soft robotics, it is essential to understand and integrate these forces. Here, we provide theoretical models of two bioinspired sys- tems governed by intermolecular forces. First, we examine polyacrylic acid (pAA) hydrogels infused with di- valent copper ions. When exposed to a strong acid stimulus, the gel releases the copper ions and exhibits rapid transient swelling at a rate exceeding the characteristic solvent absorption rate of the hydrogel. To explain this phenomenon, we develop a continuum poroelastic theory introducing the concept of gel diffusiophoresis. In this framework, molecular interactions between the gel polymer and released copper ions induces diffusion- osmotic solvent intake, which is counteracted by the diffusiophoretic deformation of the gel. This mechanism suggests that stimuli-responsive hydrogels engineered based on diffusiophoresis could enable enhanced strain rates and power output. Second, we investigate protocells — giant unilamellar lipid vesicles that preceded the first unicellular organisms. We analyze the spontaneous formation of subcompartments within these protocells. Using a continuum electrohydrodynamic theory, we demonstrate how attractive van der Waals interactions lead to the emergence of an electrohydrodynamic instability, leading to the formation of protocell colonies with enhanced mechanical stability. Our findings provide new insights into the role of chemical forces in shap- ing dynamic responses in bioinspired soft materials, paving the way for advanced materials design inspired by nature.

Host: Nadir Kaplan

No Seminar (President Day)

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No Seminar (APS March Meeting)

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Mesfin Tsige University of Akron

"Computational Approaches to Understanding and Predicting Polymer Surface Properties"

The behavior of polymer surfaces and interfaces is crucial to the performance of advanced materials in coatings, adhesives, flexible electronics, and biomedical applications. Precise control over interfacial properties requires a molecular-level understanding of adhesion, wetting, and surface energetics. In this talk, I will present our computational efforts to investigate the wetting behavior of polymer surfaces using molecular dynamics (MD) simulations. By analyzing molecular structure, functional group orientations, and interfacial energetics, we gain key insights into the mechanisms that dictate polymer surface properties. Building on this foundation, I will discuss our recent integration of machine learning (ML) techniques to enhance the predictive capabilities of polymer surface properties. While MD simulations provide detailed molecular insights, their computational cost limits high-throughput screening. To address this, we have developed ML models trained on simulation and experimental data to efficiently estimate polymer surface tensions and interfacial characteristics. This hybrid approach, combining physics-based simulations with data-driven methods, provides a powerful framework for accelerating the design and optimization of polymeric interfaces.

Host: Shengfeng Cheng

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Burcu Gurbuz Johannes Gutenberg University Mainz

“Analyzing a Mathematical Model of a Reacting Diffusing System”

The behavior of ordinary differential equation (ODE) systems has been widely studied in various chemical reaction networks, including the well-known Calvin cycle. As a key component of the photosynthetic process, the Calvin cycle plays an important role in plant physiology by driving the conversion of carbon dioxide into organic compounds. This study focuses on modeling the Calvin cycle and analyzing the qualitative properties of its dynamical solutions. Using appropriately selected parameters, the system is studied to reveal its behavior under different conditions. The simulation results are presented through graphical plots that illustrate the dynamics of the system and provide insight into its function.

Host: Uwe Tauber

Prof. Nicholas Smith University of Maryland

“Multiferroic Control in 2D Materials”

The desire for low-power computing is growing rapidly every year due to the increase in computing demands created by large-scale servers, cloud computing, and artificial intelligence. Recently, there has been much excitement surrounding spintronic devices such as magnetoelectric spin-orbit (MESO)¹ and ferroelectric spin-orbit (FESO)², which promise low-power, nonvolatile control of spin states for use in efficient cascaded logic. These devices require heterostructures with high efficiency of coupling between ferroelectric polarization and spin states, as well as extremely thin materials (<10 nm) to achieve low-voltage logic writing. MESO and FESO devices have been largely restricted to thin film choices such as Bismuth Ferrite and the heterostructure LaAlO₃/SrTiO₃, respectively. Instead of the complex growth of very thin film heterostructures, we explore Van der Waals 2D materials, allowing for the creation of a large array of novel heterostructures, down to the monolayer limit, with atomically sharp interfaces. The 2D ferroelectrics CuInP₂S₆ and In₂Se₃ demonstrate remnant polarization down to the monolayer limit, and maintain ferroelectric polarization through room temperature—with CuInP₂S₆ also exhibiting ferroionic behavior. Fe₅GeTe₂ is a stable 2D ferromagnet with complex spin texture and ferromagnetism above room temperature. Stacking these 2D ferroelectrics and ferromagnets enables the creation of artificial magnetoelectrics for voltage control of magnetism. Furthermore, stacking with a more conventional 2D material, graphene, allows for study of the mechanisms behind 2D ferroelectricity.

Host:Giti Khodaparast

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