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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Image-Based Digital Twin for Assessing the Coupled Electro-Chemo-Mechanical Behavior of Li-Ion Batteries

In energy storage materials, strong electrochemical-mechanical coupling and highly anisotropic material properties contribute to the formation and propagation of micro-cracking during charge/discharge cycling, resulting in reduced performance and service life. In this work, a digital twin is created to investigate the performance of a Li-ion battery cathode and simulate degradation accumulation. Pixel-based model construction is used to represent the complex material geometries from microstructural images supplied by the National Renewable Energy Laboratory (NREL). Because of the expected large deformation and crack opening, the reproducing kernel particle method (RKPM), a meshfree method with discretization at the image pixels, is used to approximate the field variables: electrostatic potential, concentration, and displacement. An interface modified reproducing kernel (IM-RK) is constructed by scaling a smooth kernel function with an interface-distance function to achieve strategic discontinuity types (i.e. weak discontinuities for strain discontinuities and strong discontinuities for cracks) and alleviate Gibbs oscillations near these transition zones. The discrete nature of the images' pixel points is employed throughout the model and approximation construction. The mechanical model is verified using an image-based microstructure under tensile loading. A transient electro-chemo-mechanical coupled simulation is performed to evaluate the potential micro-cracking induced degradation of the battery cathode material subjected to charge/discharge cycling.

battery degradation↗
DOE OSTI2023

MEASURING THERMALLY-INDUCED DISTORTION OF LARGE-SCALE COMPOSITE PRINTED STRUCTURES USING DIGITAL IMAGE CORRELATION

Additive manufacturing (AM) gives designers the ability to create complex part geometries without several of the limitations of traditional manufacturing. Large-Scale AM (LSAM) allows the creation of large composite structures and is a popular area of composite tooling research. Fiber-reinforced polymers are common feedstock for LSAM tooling but introduce anisotropic thermomechanical properties that can lead to the warpage of tools at autoclave conditions. Digital image correlation (DIC) has been used to measure the coefficient of thermal expansion (CTE) of LSAM parts using a novel DIC Oven design. This method was utilized to measure the CTE of LSAM structures printed using different fiber-reinforced materials and multiple geometries. Specifically, glass fiber ABS (GF-ABS) and carbon fiber ABS (CF-ABS) samples were compared as well as cube and plate geometries for each material. The temperature profile over time was also evaluated to determine how rapidly the strain of the sample increased as temperature of the DIC Oven was increased. A thermal model was developed to predict temperature profiles for various samples and identify when the samples had reached thermal equilibrium.

Corum, Tyler↗
DOE OSTI2024

Image-Based Failure Assessment of Li-Ion Batteries

In energy storage materials, strong electrochemical-mechanical coupling and highly anisotropic material properties contribute to the formation and propagation of micro-cracking during charge/discharge cycling, resulting in reduced performance and service life. In this work, a digital twin is created to investigate the performance of a heterogeneous Li-ion battery cathode and simulate degradation accumulation. Pixel-based model construction is used to represent the complex material geometries from microstructural images supplied by the National Renewable Energy Laboratory (NREL). Because of the expected large deformation and crack opening, the reproducing kernel particle method (RKPM), a meshfree method with discretization at the image pixels, is used to approximate the field variables: electrostatic potential, concentration, and displacement. An interface modified reproducing kernel (IM-RK) is constructed by scaling a smooth kernel function with an interface-distance function to achieve strategic discontinuity types (i.e. weak discontinuities for strain discontinuities and strong discontinuities for cracks) and alleviate Gibbs oscillations near these transition zones. Applications to the heterogeneous microstructures of Li-ion battery cathodes will be presented to demonstrate the effectiveness of the proposed methods. IM-RK is additionally used to inform how crack evolution in turn affects the coupled electro-chemo-mechanical behavior of the Li-ion battery cathode.

image-based modeling↗
DOE OSTI2026

Enabling the Broader Use of MOOSE for Nuclear Energy and Other Simulation

This Final Scientific and Technical Report summarizes work performed under the Phase IIA SBIR project “Enabling the Broader Use of MOOSE for Nuclear Energy and Other Simulation” (DE-SC0020906) from August 2023 through August 2025. The objective of the Phase IIA effort was to mature and harden capabilities developed during Phase II, with the goal of enabling practical interoperability between Coreform’s isogeometric analysis (IGA) technologies and the Multiphysics Object-Oriented Simulation Environment (MOOSE), while improving robustness, performance, and scalability for complex, nuclear-relevant geometries. Over the course of Phase IIA, the project established and validated an extraction-based interoperability pathway between Coreform tools and MOOSE. A combined mesh and matrix format was defined collaboratively with MOOSE developers and integrated into the solver, enabling standard MOOSE workflows to operate on data exported from Coreform’s IGA and Flex Representation Method (FRM) pipelines. Early demonstrations validated architectural compatibility using linear solid mechanics problems, while later efforts focused on benchmark testing and external use. By the end of the project period, engineers at BWXT were able to independently set up and execute a simulation using the Coreform–MOOSE workflow and provide direct feedback that informed further refinement. In parallel, substantial effort was devoted to improving the robustness of trimmed U-spline construction for complex CAD geometries. A growing test suite of nuclear-relevant models was compiled through collaboration with multiple stakeholders and used to drive extensive bug fixing and reliability improvements. These efforts resulted in improved robustness and performance, including the addition of fallback capabilities that enhance reliability when the underlying commercial CAD kernel fails. Performance-oriented work progressed later in the project, with the development and demonstration of methods to decompose complex geometries into structured subregions and updated data representations to support more efficient solver processing. Additionally, extensive enhancements to threadsafe parallel data structures and trimming operations established a foundation for scalable processing of large assemblies. Collaboration with Sandia National Laboratories on the SGM geometric modeling kernel advanced to a functioning interface test case, positioning the workflow for future kernel integration. Overall, the Phase IIA effort successfully transitioned the project from architectural proof-of-concept to externally exercised, solver-integrated capability, while clarifying remaining technical challenges related to standardization, performance optimization, and kernel integration.

42 ENGINEERING↗
DOE OSTI2023

GRIDS-Net: Inverse shape design and identification of scatterers via geometric regularization and physics-embedded deep learning

This study presents a deep learning based methodology for both remote sensing and design of acoustic scatterers. The ability to determine the shape of a scatterer, either in the context of material design or sensing, plays a critical role in many practical engineering problems. This class of inverse problems is extremely challenging due to their high-dimensional, nonlinear, and ill-posed nature. To overcome these technical hurdles, we introduce a geometric regularization approach for deep neural networks (DNN) based on non-uniform rational B-splines (NURBS) and capable of predicting complex 2D scatterer geometries in a parsimonious dimensional representation. Then, this geometric regularization is combined with physics-embedded learning and integrated within a robust convolutional autoencoder (CAE) architecture to accurately predict the shape of 2D scatterers in the context of identification and inverse design problems. Further, an extensive numerical study is presented in order to showcase the remarkable ability of this approach to handle complex scatterer geometries while generating physically-consistent acoustic fields. The study also assesses and contrasts the role played by the (weakly) embedded physics in the convergence of the DNN predictions to a physically consistent inverse design.

42 ENGINEERING↗
DOE OSTI2024

From +I to +IV, Alkalis to Actinides: Capturing Cations across the Periodic Table with Keggin Polyoxometalate Ligands

Coordination chemistry trends across the periodic table are often difficult to probe experimentally due to limitations in finding a versatile but consistent chelating platform that can accommodate various elements without changing its coordination mode. Herein, we present new metal/ligand systems covering a wide range of ionic radii, charges, and elements. Five different ligands derived from the Keggin structure (HBW 11 O 39 8– , PW 11 O 39 7– , SiW 11 O 39 8– , GeW 11 O 39 8– , and GaW 11 O 39 9– ) were successfully crystallized with six different cations (Na + , Sr 2+ , Ba 2+ , La 3+ , Ce 4+ , and Th 4+ ) and characterized by single-crystal X-ray diffraction. Twenty-five new compounds were obtained by using Cs + as the counterion, yielding a consistent base formula of Cs x [M(XW 11 O 39 ) 2 ]·nH 2 O. Despite having a similar first-coordination sphere geometry (i.e., 8-coordinated), the nature of the central cation was found to impact the long-range geometry of the complexes. This unique crystallographic data set shows that, despite the traditional consensus, the local geometry of the cation (i.e., metal–oxygen bond distance) is not enough to depict the full impact of the complexed metal ion. The bending and twisting of the complexes, as well as ligand–ligand distances, were all impacted by the nature of the central cation. We also observed that counterions play a critical role by stabilizing the geometry of the M(XW 11 ) 2 complex and directing complex–complex interactions in the lattice. We also define certain structural limits for this type of complex, with the large Ba 2+ ion seemingly approaching those limits. Finally, this study thus lays the foundation for capturing the coordination chemistry of other rarer elements across the periodic table such as Ra 2+ , Ac 3+ , Bk 4+ , Cf 3+ , etc.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Simulation scaling studies of reactor core two-phase flow using direct numerical simulation

Tremendous growth in supercomputing power in recent years has resulted in the emergence of high-resolution flow analysis methods as an advanced research tool to evaluate single and two-phase flow behavior. In particular, unstructured mesh-based methods have been applied to analyze flows in complex reactor core geometries, including those of light water reactors (LWR). The finite-element based code, PHASTA, is utilized to perform large-scale simulations of two-phase bubbly flows in LWR geometries. Given the large computational cost of direct numerical simulation (DNS) coupled with interface tracking methods (ITM), typical domains encompass a portion of a single subchannel. In the presented research, the state-of-the-art analysis of turbulent two-phase flows in complex LWR subchannel geometries are demonstrated at both prototypical reactor parameters as well as scaled low pressure conditions. Three different cases are studied, a high-pressure simulation in prototypical reactor subchannel geometry, a low-pressure case in prototypical geometry and a final low-pressure case in a geometry scaled up to conserve the ratio between the bubble size and the domain pitch. Utilizing advanced statistical processing tools, these simulation conditions are compared to shed light on the relevancy of two-phase flow characteristics given the significant differences between LWR and low-pressure conditions. These findings can lead to the generation of useful guiding principles when researchers need to scale the two-phase flow behavior captured at low pressure and temperature conditions to those at reactor operating conditions.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2023

Contribution of the catalytic dyad of SARS-CoV-2 main protease to binding covalent and noncovalent inhibitors

The effect of mutations of the catalytic dyad residues of SARS-CoV-2 main protease (MPro WT ) on the thermodynamics of binding of covalent inhibitors comprising nitrile [nirmatrelvir (NMV), NBH2], aldehyde (GC373), and ketone (BBH1) warheads to MPro is examined together with room temperature X-ray crystallography. When lacking the nucleophilic C145, NMV binding is ~400-fold weaker corresponding to 3.5 kcal/mol and 13.3 °C decrease in free energy (ΔG) and thermal stability (T m ), respectively, relative to MPro WT . The H41A mutation results in a 20-fold increase in the dissociation constant (K d ), and 1.7 kcal/mol and 1.4 °C decreases in ΔG and T m , respectively. Increasing the pH from 7.2 to 8.2 enhances NMV binding to MPro H41A , whereas no significant change is observed in binding to MPro WT . Structures of the four inhibitor complexes with MPro 1-304/C145A show that the active site geometries of the complexes are nearly identical to that of MPro WT with the nucleophilic sulfur of C145 positioned to react with the nitrile or the carbonyl carbon. These results support a two-step mechanism for the formation of the covalent complex involving an initial non-covalent binding followed by a nucleophilic attack by the thiolate anion of C145 on the warhead carbon. Noncovalent inhibitor ensitrelvir (ESV) exhibits a binding affinity to MPro WT that is similar to NMV but differs in its thermodynamic signature from NMV. The binding of ESV to MPro C145A also results in a significant, but smaller, increase in K d and decrease in ΔG and T m , relative to NMV.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

GEOMWRITER - A Workflow for Automatically Generating MCNP Geometry for Neutron Guide Simulations

This report describes the functionality of the geomwriter.py script, which is a python script for producing complex MCNP CSG geometries from the IGES CAD format. It is specifically written to handle neutron supermirror guides, but can handle more complex objects through utilizing a convex hull algorithm. This work flow reduces the amount of time spent on generating the surface definitions for a complex neutron guide system with hundreds of segments such that changes to the neutron guide system design in McStas can be rapidly incorporated into an MCNP model and integrated with the shielding geometry present in that model.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2024

Comprehensive Synthesis and Structural Trends in Tetramethyl Diglycolamide (TMDGA) Nitrate Complexes with Lanthanides and Americium

Complexes of N,N,N',N'-tetramethyl diglycolamide (TMDGA), a hydrophilic diglycolamide (DGA) proposed as an aqueous phase holdback reagent, have been crystallized for the majority of the lanthanide series (excluding promethium), yttrium, and americium to deepen our structural understanding of trivalent metal ion (M 3+ ) DGA coordination compounds in the presence of nitrate counter-anions. The presented collection of 16 complexes with accompanying single-crystal structures, taking formulas [M(TMDGA) 3 ][M(NO 3 ) 6 ] (M = La, Ce, Pr, Nd, Sm, Am), [M(TMDGA) 3 ][M(NO 3 ) 5 (H 2 O)] 1–x [M(NO 3 ) 4 (H 2 O) 2 ] x (NO 3 ) 1+x (M = Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb), [M(TMDGA) 3 ] 2 [M(NO 3 ) 4 (H 2 O) 2 ] 0.75 [M(NO 3 ) 5 (H 2 O)] 1.25 (NO 3 ) 2.75 ·H 2 O (M = Lu), and [M(TMDGA) 3 ][M(NO 3 ) 5 (H 2 O)](NO 3 )·CH 3 OH (M = Y) were all synthesized via solvent diffusion of reaction mixtures containing the metal nitrate M(NO 3 ) 3 ·nH 2 O and TMDGA. Single-crystal X-ray diffraction analyses of these new structures show that each TMDGA complex comprises of three TMDGA ligands coordinating the metal ion via carbonyl and etheric oxygen atoms forming [M(TMDGA) 3 ] 3+ cations. Spectroscopy measurements under high pressure displayed notable differences in the f → f transition shifting between that of Nd(III) and Am(III). Shifting of transitions by 2.0 nm were observed in Nd up to 8.50 ± 0.09 GPa, while Am saw shifting between 11.0 to 13.5 nm at pressures up to 20.06 ± 1.90 GPa. The local geometry in these complexes is a distorted spherical capped square antiprism (CSAPR-9) except for of the yttrium complex, which exhibits a distorted spherical tricapped trigonal prismatic (TCTPR-9) geometry. Further, the anions that form concomitantly with the TMDGA complexes are composed of hexanitrato species for the early lanthanide ions (lanthanum to samarium); whereas the remaining smaller lanthanides did not possess sufficiently large ionic radii to coordinate six bidentate nitrate anions, instead, one or two nitrate anions are situated in the outer sphere. The systematic progression of changes in the anionic environments of these complexes outlines the changing coordination habits afforded by the lanthanide contraction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Role of High-Spin Species and Pendant Amines in Electrocatalytic Alcohol Oxidation by a Nickel Phosphine Complex

We report the development of active and efficient electrocatalysts for oxidation of alcohols using earth-abundant metals will aid the progress towards a renewable energy economy. Here we present a detailed mechanistic study of electrocatalytic benzyl alcohol oxidation by a molecular nickel complex containing pendant amines using a combination of kinetic studies, NMR spectroscopy, and density functional theory. The catalyst preferentially binds alcohol in high-spin octahedral geometry, but this complex is not readily deprotonated by exogeneous base and inhibits catalysis. Dissociation of one or more solvent ligands returns the complex to a low-spin state that can be deprotonated. Kinetic modeling indicates the off-cycle high-spin intermediate lowers the catalytic turnover frequency by a factor of eight, suggesting that substantial gains in activity can be attained by improvements to the catalyst coordination geometry. In a second finding, we demonstrate the pendant amine of the catalyst only functions as a proton relay for the potential-determining step, oxidation of a nickel hydride intermediate, but does not have a substantial impact on the overall rate for oxidation of benzyl alcohol to benzaldehyde. This result contradicts the common expectation for pendant amines to participate in rate-limiting proton transfer reactions.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Fourier Analysis and Loss Modeling for Inductive Wireless Electric Vehicle Charging with Reduced Stray Field

With the growth of electric vehicle (EV) popularity, different charging options to increase user convenience and reduce charging times are being considered and researched. Among these, inductive wireless power transfer (WPT) systems for EVs are being designed to meet specifications such as stray field, power level, efficiency, misalignment tolerance, and ground clearance, which are all heavily influenced by the coil geometry. The proposed Fourier Analysis Method (FAM) is an analytical method to directly design coil geometries to meet stray field and power level requirements through an optimization of Fourier basis function coefficients. The outputs of the optimization are complex, planar coil geometries that meet the power level and stray field constraints with minimized loss factors. Contours of these potentials determine the coil conductor paths and loss models predict the system efficiency and performance over misalignment. The Fourier representation of the geometry is used to conveniently calculate the coupling over misalignment, external proximity effect loss, and ferrite loss. A 6.6 kW prototype WPT system with low stray field and high efficiency is built from the optimization results to validate the models and showcase the usefulness of the FAM design approach.

33 ADVANCED PROPULSION SYSTEMS↗
DOE OSTI2026

The Structure-Properties Relationship of Alternative Bismaleimide Variants for Candidacy for Additive Manufacturing

Modernizing the manufacturing of high-performance polymer foams such as amino-poly(oxadiazole) bismaleimide (APO-BMI), a bismaleimide resin with superior thermal and compressive strength that incorporates additive manufacturing (AM) techniques, is crucial for its applications, but the parameters for AM can be challenging based on the physical properties of the associated monomer. For our applications, selective laser sintering (SLS) is typically used. SLS is a 3D printing technique that allows for complex shapes and geometries without structural supports while also providing high resolution material. However, printing thermosets like APO-BMI with SLS is challenging due to the complex melting and curing considerations required when selecting parameters. Additionally, the temperature difference between melting and curing of APO-BMI is over a hundred º C, which makes selecting a sintering window especially difficult. This work explores structural modifications of APO-BMI that may be more amenable for selective laser sintering. The effects of how different structural changes such as substitution pattern, heteroatom identity in the bridge, and bridge length affect the thermal properties of the material were also compared. All APO variants were found to have a smaller temperature window between the melting and curing peaks based on differential scanning calorimetry (DSC) which is advantageous for SLS. Small structural changes significantly altered the melting and curing properties of APO. Additionally, DSC revealed significant polymorphisms in APO-BMI and other APO variants which could be attributed to differences in thermal history and would need to be considered when adapting for SLS.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Chain trajectories, domain shapes, and terminal boundaries in block copolymers

The packing geometry of macromolecules in complex mesophases is of key importance to self-organization in synthetic and biological soft materials. While approximate or heuristic models rely on often-untested assumptions about how flexible molecules “fit in” to distinct locations of complex assemblies, physical assemblies derive from ensembles of fluctuating conformations, obscuring the connection between mesophase geometry and the underlying arrangements. Here, we present an approach to extract and analyze features of molecular packing in diblock block copolymer (BCP) melts, a prototypical soft matter system, based on the statistical description of chain conformations in self-consistent field (SCF) theory. We show how average BCP chain trajectories in ordered morphologies can be analyzed from the SCF-derived orientational order parameter of chain segments. We use these extracted trajectories to analyze the features of local packing geometry, including chain bending and tilt, as well as the terminal boundaries that delineate distinct domains in ordered BCP morphologies. In conclusion, we illustrate this analysis by focusing on measurable features of packing frustration in 2D (columnar) and 3D (spherical and bicontinuous) morphologies, notably establishing an explicit link between chain conformations in complex morphologies and their medial geometry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Synthesis, Characterization, and Water Oxidation Activity of Isomeric Ru Complexes

The synthesis and characterization of the isomeric ruthenium complexes with the general formula cis- and trans-[Ru(trpy)(qc)X] n+ (trpy is 2,2':6',2"-terpyridine, qc is 8-quinolinecarboxylate, cis-1 and trans-1, X = Cl, n = 0; cis-2 and trans-2, X=OH2, n = 1) with respect to the relative disposition of the carboxylate and X ligands are reported. For comparison purposes, another set of ruthenium complexes with general formula cis- and trans-[Ru(trpy)(pic)(OH 2 )]+ (pic is 2-picolinate (cis-3, trans-3)) have been prepared. The complexes with a qc ligand show a more distorted geometry compared to the complexes with a pic ligand. In all of the cases, the trans isomers show lower potential values for all of the redox couples relative to the cis isomers. Furthermore, complexes cis-2 and trans-2 with six-member chelate rings show higher catalytic activity than cis-3 and trans-3. Overall, it was shown that the electronic perturbation to the metal center exerted by different orientation and geometry of the ligands significantly influences both redox properties and catalytic performance.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

Synthesis, Structure, and Redox Reactivity of Ni Complexes Bearing a Redox and Acid–Base Non-innocent Ligand with Ni II , Ni III , and Ni IV Formal Oxidation States

Here, a series of Ni complexes bearing a redox and acid–base noninnocent tetraamido macrocyclic ligand, H 4 -(TAML-4) {H 4 -(TAML-4) = 15,15-dimethyl-5,8,13,17-tetrahydro-5,8,13,17-tetraaza-dibenzo[a,g]cyclotridecene-6,7,14,16-tetraone}, with formal oxidation states of Ni II , Ni III , and Ni IV were synthesized and characterized structurally and spectroscopically. The X-ray crystallographic analysis of the Ni complexes revealed a square planar geometry, and the [Ni(TAML-4)] complex with the formal oxidation state of Ni IV was characterized to be [Ni III (TAML-4 •+ )] with the oxidation state of the Ni III ion and the one-electron oxidized TAML-4 ligand, TAML-4 •+ . The Ni III oxidation state and the TAML-4 radical cation ligand, TAML-4 •+ , were supported by X-ray absorption spectroscopy and density functional theory calculations. The reversible interconversions between [Ni II (TAML-4)] 2– and [Ni III (TAML-4)] − and between [Ni III (TAML-4)] − and [Ni III (TAML-4 •+ )] were demonstrated in spectroelectrochemical measurements as well as in chemical oxidation and reduction reactions. The reactivities of [Ni III (TAML-4)] − and [Ni III (TAML-4 •+ )] were then investigated in hydride transfer reactions using NADH analogs. Hydride transfer from 9,10-dihydro-10-methylacridine (AcrH 2 ) to [Ni III (TAML-4 •+ )] was found to proceed via electron transfer (ET) from AcrH 2 to [Ni III (TAML-4 •+ )] with no deuterium kinetic isotope effect (k H /k D = 1.0(2)). In contrast, hydride transfer from AcrH 2 to [NiIII(TAML-4)] − proceeded much more slowly via a concerted proton-coupled electron transfer (PCET) process with k H /k D = 7.0(5). In the latter reaction, an electron and a proton were transferred to the Ni III center and the TAML-4 ligand, respectively. The mechanisms of the ET by [Ni III (TAML-4 •+ )] and the concerted PCET by [Ni III (TAML-4)] − were ascribed to the different redox potentials of the Ni complexes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Spatially co-registered wide-field nonlinear optical imaging of living and complex biosystems in a total internal reflection geometry

Nonlinear optical microscopy that leverages an objective based total internal reflection (TIR) excitation scheme is an attractive means for rapid, wide-field imaging with enhanced surface sensitivity. Through select combinations of distinct modalities, one can, in principle, access complementary chemical and structural information for various chemical species near interfaces. Here, we report a successful implementation of such a wide-field nonlinear optical microscope system, which combines coherent anti-Stokes Raman scattering (CARS), two-photon fluorescence (TPF), second harmonic generation (SHG), and sum frequency generation (SFG) modalities on the same platform. The intense optical fields needed to drive these high order nonlinear optical processes are achieved through the use of femtosecond pulsed light in combination with the intrinsic field confinement induced by TIR over a large field of view. The performance of our multimodal microscope was first assessed through the experimental determination of its chemical fidelity, intensity and polarization dependences, and spatial resolution using a set of well-defined model systems. Subsequently, its unique capabilities were validated through imaging complex biological systems, including Hydrangea quercifolia pollen grains and Pantoea sp. YR343 bacterial cells. Specifically, the spatial distribution of different molecular groups in the former was visualized via vibrational contrast mechanisms of CARS, whereas co-registered TPF imaging allowed the identification of spatially localized intrinsic fluorophores. We further demonstrate the feasibility of our microscope for wide-field CARS imaging on live cells through independent characterization of cell viability using spatially co-registered TPF imaging. Overall, this approach to TIR enabled wide-field imaging is expected to provide new insights into bacterial strains and their interactions with other species in the rhizosphere in a time-resolved and chemically selective manner.

47 OTHER INSTRUMENTATION↗
DOE OSTI2025

Comparison Study of Conventional and Adaptive Mesh Refinement in Organic Material Decomposition Models

This study compares conventional mesh refinement techniques, specifically Uniform Mesh Refinement (UMR), with a new Adaptive Mesh Refinement (AMR) method, applied to Organic Material Decomposition (OMD) models. The proposed benefit of AMR is that only areas that require refinement, based on minimizing a specific field gradient, are refined thus decreasing model wall time compared to conventional UMR methods. This work specifically focuses on comparing UMR and AMR methods on decomposing (both No-Flow and Porous-Flow material models) Polymeric Methylene Diisocyanate (PMDI) polyurethane foam. Throughout the work, the geometry increased in complexity to assess the refinement methods performance at varying levels geometric intricacy. While AMR has been shown to work well in a variety of applications, the UMR approach proved to be computationally faster, for many of the geometries and foam decomposition models, than AMR. However, it was observed that at higher levels of refinement, greater than 3 UMR, AMR begins to be computationally better. Additionally, the settings used to perform AMR greatly impact its performance, and lessons learned, in terms of OMD models, are shared. Due to physics involved in material decomposition, specifically the evolution of state variables, these problems don’t fully benefit from the advantages of AMR.

36 MATERIALS SCIENCE↗