Strong, tough, and lightweight materials are needed for a myriad of structural and functional applications in Space systems and on Earth in diverse strategic fields that range from biomedical, to buildings, transportation and energy generation, or storage. These new, yet to be developed materials, should exhibit unprecedented combinations of strength and toughness, while being manufacturable at low cost and in high volume. Numerous processing techniques have been proposed to produce these materials, but frequently cannot provide the degree of microstructural control needed to manipulate and optimize the property profile, particularly of multifunctional materials. One technique, which holds great promise in fabricating novel materials with great structural control, is freeze-casting, a relatively inexpensive procedure which also provides a means to mimic complex, efficient natural materials with hierarchical designs over several length-scales. The fundamental science and understanding of this processing technique is limited, because, on Earth, convection and sedimentation complicate both the interpretation of experimental results and their comparison with theoretical predications. Avoiding these in space, following four scientific goals will be pursued. To reveal on Earth (Aim 1, completed, see Final Report) and in Space (Aim 2, to be performed, see Final Report) the underlying fundamental materials science of freeze casting and establish a realistic model for structure formation in multifaceted crystal nucleation and growth. Aim 3: Develop predictive models to identify the most promising material processing combinations and conditions to optimize material performance. Aim 4: Translate the results of (1-3) into structure-property-processing correlations for highly porous, freeze-cast scaffolds (polymer, ceramic, metal, and composite) made on Earth. Data obtained and computational models were made available to the NASA Physical Sciences Informatics to make the data accessible to the global community and help translate research into application for an accelerated pace of advanced-materials discovery, innovation, manufacture, and commercialization.

In our study of “Structure-Property-Processing Correlations in Freeze-Cast Biomimetic Materials,” we quantify both the to date little studied complex, dynamic ice crystal growth phenomena and the ice-templated hierarchical architecture of freeze-cast scaffolds as well as the various cell wall surface features, not only because they are of interest from a fundamental science point of view but also because the ridges, pillars, bridges, and fibrillation observed in freeze-cast biopolymer scaffolds frequently result in highly desirable features for biomedical applications. In peripheral nerve repair we observe, for example, that not only the highly aligned porosity, but also cell wall surface ridges serve as powerful structural cues to guide regenerating neurites from one end to the other of the freeze cast regenerative scaffold. While cell wall surface features, such as these regularly spaced ridges, had been observed under specific processing conditions in a range of freeze-cast biopolymers, we found that the fundamental science and underlying principles that govern their formation remain unknown ant that, in fact, more generally, ice crystal growth from the liquid phase and binary or ternary polymer solutions had hardly ever been studied and simulated. We therefore started to systematically study structure-property-processing correlations under well-defined conditions and complement experiments with phase-field (PF) simulations, which are essential to fully understand the observed phenomena and formulate robust and predictive structure-property-processing correlations for the design and manufacture of freeze-cast materials for a great variety of applications that range from biomedical to energy generation and storage, to catalysis, filtration, optical and acoustical absorption, and thermal insulation.

In the first instance, we experimentally determined structure-property-processing correlations for scaffolds freeze-cast from collagen- and chitosan-based scaffolds both in the dry and the fully hydrated states. The results obtained for both ‘smooth’ and ‘fibrillar’ polymer systems contributed to a better understanding of the likely sequence of events during the solidification process and the resulting ice-templated feature formation in the polymer phase. Noteworthy are also discoveries made with respect to the dependence of the mechanical properties, such as modulus, yield strength, and toughness, on processing conditions such as applied cooling rates and mold height, and the resulting structural features such as lamellar spacing (length of the short pore axis of the rectangular pores), and cell wall thickness, and scaffold reinforcing features such as ridges, bridges, and pillars, and preferential molecular alignment with the freezing direction.

These systematic experimental studies were key first steps on the path to our long-term goal of this study: to bridge the current critical knowledge gap, which is the lack of understanding of the fundamental mechanisms of structure formation, initially in freeze-cast polymers and later, also, in particle-based ceramic and metal systems. Knowing how the size and shape of the pores in freeze-cast materials are defined and can be controlled by controlling the ice crystal growth, the need for a better fundamental understanding of the physics of directional solidification in aqueous systems became even more obvious. We overcame the challenge of the absence of equilibrium phase diagrams and also determined concentration- and temperature-dependent diffusion coefficients and viscosities for our ternary chitosan-acetic acid-water system, and further reduced system complexity in support of the PF simulation effort by focusing in our 2D and 3D studies on the binary systems trehalose-water and sucrose-water systems, for which the fundamental properties are known and documented.

Since crystal growth in bulk samples are difficult to observe and characterize in situ, diffusive crystal growth under terrestrial conditions is typically studied in 2D with thin samples. While we initially focused on the traditional light microscopy perpendicular to the moving freezing front – primarily to observe both in aqueous and dimethyl sulfoxide (DMSO)-based systems the formation of Mullins-Sekerka instabilities, and their subsequent reorganization into an array of cells or dendrites, as a function of polymer concentration and cooling rates (which is equal to the product of velocity and thermal gradient in directional solidification) – we subsequently applied in situ X-ray tomoscopy, which is continuous, time-resolved tomography, as the more suitable tool to analyze in 3D the dynamics of both crystal growth and structure formation phenomena. With synchrotron-based tomoscopy, we were able to investigate and determine the kinetics of the ice-phase growth and the mechanisms by which the growing ice-crystals, thus ice phase, templates the polymer phase into a cellular solid with a range of cell wall surface features, while the polymer is increasingly upconcentrated and transitions from an aqueous solution to a glassy solid. Overall, our observation is that 2D thin film experiments should, whenever possible, be complemented by 3D in situ tomoscopy experiments, because it is frequently impossible to extrapolate structure formation phenomena from 2D thin film observations to bulk materials; DMSO is an excellent example for that.

As critical as 3D in situ X-ray tomoscopy is for our quantitative studies, and the observation also of transient events during the directional solidification in freeze casting, are the 3D PF simulations, which were performed for aqueous and DMSO-based systems. Remarkably, the PF simulations of anisotropic, faceted ice crystal growth binary aqueous systems with a dilute impurity (trehalose, sucrose in the case of water, and water in the case of DMSO), reproduced for the first time the various salient features of freeze-cast structures: from the cellular scaffold structure with their characteristic lamellar spacing to the cell wall surface features, such as ridges, which are templated by secondary instabilities on the ice crystal’s basal plane. The value of the 3D phase-field simulations is immense, since they enable us to investigate little studied and not yet modeled mechanisms of hierarchical microstructure formation and cell wall material self-assembly, both of which define anisotropy, property profile, and overall performance of freeze-cast materials. Our results highlight the crucial role of both the solid-liquid interface free-energy and the interface kinetics in structure formation. They also highlight other potentially important physical effects neglected in the phase-field model, such as fluid flow generated by the expansion of ice, which may play a more secondary role in structure formation. From a practical point of view, the ability to accurately predict the detailed temporal evolution of interface structures under prescribed growth conditions is highly informative for optimizing processing routes and material properties.

In preparation of the System Requirements Review (SRR) and microgravity experiments, two Science Requirements Documents (SRDs) were prepared for the CASTing project: first, one for the Pore Formation and Mobility Investigation (PFMI) Insert supported by Redwire Space; then a second, insert-agnostic version, to explore also a newly available platform, MaRVIn of Tec-Masters, Inc. (TMI). A successful System Requirements Review (SRR) to determine flight readiness took place at the Marshall Space Flight Center (MSFC) on October 16, 2024.

Strong, tough, and lightweight materials are needed for a myriad of structural and functional applications in Space systems and on Earth in diverse strategic fields that range from biomedical, to buildings, transportation and energy generation, or storage. These new, yet to be developed materials, should exhibit unprecedented combinations of strength and toughness, while being manufacturable at low cost and in high volume. Numerous processing techniques have been proposed to produce these materials, but frequently cannot provide the degree of microstructural control needed to manipulate and optimize the property profile, particularly of multifunctional materials. One technique, which holds great promise in fabricating novel materials with great structural control, is freeze-casting, a relatively inexpensive procedure which also provides a means to mimic complex, efficient natural materials with hierarchical designs over several length-scales. To date, the fundamental science and understanding of this processing technique is limited, because, on Earth, convection and sedimentation complicate both the interpretation of experimental results and their comparison with theoretical predications. Avoiding these in space, following four scientific goals will be pursued. To reveal on Earth (Aim 1) and in Space (Aim 2) the underlying fundamental materials science of freeze casting and establish a realistic model for structure formation in multifaceted crystal nucleation and growth. Aim 3: Develop predictive models to identify the most promising material processing combinations and conditions to optimize material performance. Aim 4: Translate the results of (1-3) into structure-property-processing correlations for highly porous, freeze-cast scaffolds (polymer, ceramic, metal, and composite) made on Earth. Data obtained and computational models will be made available to the NASA Physical Sciences Informatics to make the data accessible to the global community and help translate research into application for an accelerated pace of advanced-materials discovery, innovation, manufacture, and commercialization.

In some cases, when water-based biopolymer solutions are freeze cast, the final freeze-cast materials and scaffolds exhibit features that are very unusual for directionally solidified materials; they exhibit, for example: i) highly aligned and regularly spaced ridges of uniform height, ‘jellyfish’-like caps and arrays, and ‘tentacles’-like features parallel to the direction of solidification; ii) fibrillar pillars and bridges in fiber composites; and iii) even enhanced fibrillation, a form of self-assembly and structure formation in biopolymers such as collagen.

In our study of “Structure-Property-Processing Correlations in Freeze-Cast Biomimetic Materials,” we quantify both the (to date) little studied, complex, dynamic ice crystal growth phenomena and the ice-templated hierarchical architecture of freeze-cast scaffolds, as well as the various cell wall surface features, not only because they are of interest from a fundamental science point of view but also because the ridges, pillars, bridges, and fibrillation observed in freeze-cast biopolymer scaffolds frequently result in highly desirable features for biomedical applications. In peripheral nerve repair we observe, for example, that not only the highly aligned porosity, but also cell wall surface ridges, serve as powerful structural cues to guide regenerating neurites from one end to the other of the freeze cast regenerative scaffold. While cell wall surface features, such as these regularly spaced ridges, had been observed under specific processing conditions in a range of freeze-cast biopolymers, we found that the fundamental science and underlying principles that govern their formation remain unknown and that, in fact more generally, ice crystal growth from the liquid phase and binary or ternary polymer solutions had hardly ever been studied and simulated. We therefore started to systematically study structure-property-processing correlations under well-defined conditions and complement experiments with phase-field (PF) simulations, which are essential to fully understand the observed phenomena and formulate robust and predictive structure-property-processing correlations for the design and manufacture of freeze-cast materials for a great variety of applications that range from biomedical, to energy generation and storage, to catalysis, filtration, optical and acoustical absorption, and thermal insulation.

In the first instance, we experimentally determined structure-property-processing correlations for scaffolds freeze-cast from collagen- and chitosan-based scaffolds both in the dry and the fully hydrated states. The results obtained for both ‘smooth’ and ‘fibrillar’ polymer systems contributed to a better understanding of the likely sequence of events during the solidification process and the resulting ice-templated feature formation in the polymer phase. Noteworthy are also discoveries made with respect to the dependence of the mechanical properties, such as modulus, yield strength, and toughness, on processing conditions such as applied cooling rates and mold height, and the resulting structural features such as lamellar spacing (length of the short pore axis of the rectangular pores), and cell wall thickness, and scaffold reinforcing features such as ridges, bridges, and pillars, and preferential molecular alignment with the freezing direction.

These systematic experimental studies were key first steps on the path to our long-term goal of this study: to bridge the current critical knowledge gap, which is the lack of understanding of the fundamental mechanisms of structure formation, initially in freeze-cast polymers and later also in particle-based ceramic and metal systems. Knowing how the size and shape of the pores in freeze-cast materials are defined and can be controlled by controlling the ice crystal growth, the need for a better fundamental understanding of the physics of directional solidification in aqueous systems became even more obvious. We overcame the challenge of the absence of equilibrium phase diagrams and also determined concentration- and temperature-dependent diffusion coefficients and viscosities for our ternary chitosan-acetic acid-water system, and further reduced system complexity in support of the PF simulation effort by focusing in our 2D and 3D studies on the binary systems trehalose-water and sucrose-water systems, for which the fundamental properties are known and documented.

Since crystal growth in bulk samples is difficult to observe and characterize in situ, diffusive crystal growth under terrestrial conditions is typically studied in 2D with thin samples. While we initially focused on the traditional light microscopy perpendicular to the moving freezing front primarily to observe both in aqueous and DMSO-based systems the formation of Mullins-Sekerka instabilities and their subsequent reorganization into an array of cells or dendrites as a function of polymer concentration and cooling rates, which is equal to the product of velocity and thermal gradient in directional solidification, we now apply in situ X-ray tomoscopy, which is continuous, time-resolved tomography, as the more suitable tool to analyze in 3D the dynamics of both crystal growth and structure formation phenomena. With synchrotron-based tomoscopy, we have since Year 3 been able to investigate and determine the kinetics of the ice-phase growth and the mechanisms by which the growing ice-crystals, thus ice phase, templates the polymer phase into a cellular solid with a range of cell wall surface features, while the polymer is increasingly upconcentrated and transitions from an aqueous solution to a glassy solid. Overall, our observation is that 2D thin film experiments should, whenever possible, be complemented by 3D in situ tomoscopy experiments, because it is frequently impossible to extrapolate structure formation phenomena from 2D thin film observations to bulk materials; DMSO is an excellent example.

As critical as 3D in situ X-ray tomoscopy is for our quantitative studies and the observation also of transient events during the directional solidification in freeze casting, are the 3D PF simulations, which started in Year 2 for aqueous systems. Remarkably, the PF simulations of anisotropic, faceted ice crystal growth binary aqueous systems with a dilute impurity (trehalose, sucrose), reproduced for the first time the various salient features of freeze-cast structures: from the cellular scaffold structure with their characteristic lamellar spacing to the cell wall surface features such as ridges, which are templated by secondary instabilities on the ice crystal’s basal plane. The value of the 3D phase-field simulations is immense, since they enable us to investigate little studied and not yet modeled mechanisms of hierarchical microstructure formation and cell wall material self-assembly, both of which define anisotropy, property profile, and overall performance of freeze-cast materials. Our results highlight the crucial role of both the solid-liquid interface free-energy and the interface kinetics in structure formation. They also highlight other potentially important physical effects neglected in the phase-field model, such as fluid flow generated by the expansion of ice may play a more secondary role in structure formation. The PF-modelling effort was in 2022 (Year 5) extended to DMSO-based material systems; first results were reported in 2023 (Year 6). From a practical point of view, the ability to accurately predict the detailed temporal evolution of interface structures under prescribed growth conditions is critical for optimizing processing routes and material properties. In preparation for the microgravity experiments, two Science Requirements Documents (SRDs) have been prepared for the CASTing project: one for the Pore Formation and Mobility Investigation (PFMI) Insert and a second insert-agnostic version.

Strong, tough, and lightweight materials are needed for a myriad of structural and functional applications in Space systems and on Earth in diverse strategic fields that range from biomedical, to buildings, transportation and energy generation, or storage. These new, yet to be developed materials, should exhibit unprecedented combinations of strength and toughness, while being manufacturable at low cost and in high volume. Numerous processing techniques have been proposed to produce these materials, but frequently cannot provide the degree of microstructural control needed to manipulate and optimize the property profile, particularly of multifunctional materials. One technique, which holds great promise in fabricating novel materials with great structural control, is freeze-casting, a relatively inexpensive procedure which also provides a means to mimic complex, efficient natural materials with hierarchical designs over several length-scales. To date, the fundamental science and understanding of this processing technique is limited, because, on Earth, convection and sedimentation complicate both the interpretation of experimental results and their comparison with theoretical predications. Avoiding these in space, following four scientific goals will be pursued. To reveal on Earth (Aim 1) and in Space (Aim 2) the underlying fundamental materials science of freeze casting and establish a realistic model for structure formation in multifaceted crystal nucleation and growth. Aim 3: Develop predictive models to identify the most promising material processing combinations and conditions to optimize material performance. Aim 4: Translate the results of (1-3) into structure-property-processing correlations for highly porous, freeze-cast scaffolds (polymer, ceramic, metal, and composite) made on Earth. Data obtained and computational models will be made available to the NASA Physical Sciences Informatics to make the data accessible to the global community and help translate research into application for an accelerated pace of advanced-materials discovery, innovation, manufacture, and commercialization.

In some cases, when water-based biopolymer solutions are freeze-cast, the final freeze-cast materials and scaffolds exhibit features that are very unusual for directionally solidified materials; they exhibit, for example: i) highly aligned and regularly spaced ridges of uniform height, ‘jellyfish’-like caps and arrays, and ‘tentacles’-like features parallel to the direction of solidification, and ii) fibrillar pillars and bridges in fiber composites, and even enhanced iii) fibrillation, a form of self-assembly and structure formation in biopolymers such as collagen.

In our study of “Structure-Property-Processing Correlations in Freeze-Cast Biomimetic Materials,” we quantify both the (to date, little studied) complex, dynamic ice crystal growth phenomena and the ice-templated hierarchical architecture of freeze-cast scaffolds, as well as the various cell wall surface features, not only because they are of interest from a fundamental science point of view but also because the ridges, pillars, bridges, and fibrillation observed in freeze-cast biopolymer scaffolds frequently result in highly desirable features for biomedical applications. In peripheral nerve repair, we observe, for example, that not only the highly aligned porosity, but also cell wall surface ridges serve as powerful structural cues to guide regenerating neurites from one end to the other of the freeze-cast regenerative scaffold. While cell wall surface features, such as these regularly spaced ridges, had been observed under specific processing conditions in a range of freeze-cast biopolymers, we found that the fundamental science and underlying principles that govern their formation remain unknown and that, in fact, more generally, ice crystal growth from the liquid phase and binary or ternary polymer solutions had hardly ever been studied and simulated. We therefore started to systematically study structure-property-processing correlations under well-defined conditions and complement experiments with phase-field (PF) simulations, which are essential to fully understand the observed phenomena and formulate robust and predictive structure-property-processing correlations for the design and manufacture of freeze-cast materials for a great variety of applications that range from biomedical to energy generation and storage, to catalysis, filtration, optical and acoustical absorption, and thermal insulation.

In the first instance, we experimentally determined structure-property-processing correlations for scaffolds freeze-cast from collagen- and chitosan-based scaffolds, both in the dry and the fully hydrated states. The results obtained for both ‘smooth’ and ‘fibrillar’ polymer systems contributed to a better understanding of the likely sequence of events during the solidification process and the resulting ice-templated feature formation in the polymer phase. Noteworthy are also discoveries made with respect to the dependence of the mechanical properties, such as modulus, yield strength, and toughness, on processing conditions such as applied cooling rates and mold height, and the resulting structural features such as lamellar spacing (length of the short pore axis of the rectangular pores), and cell wall thickness, and scaffold reinforcing features such as ridges, bridges, and pillars, and preferential molecular alignment with the freezing direction.

These systematic experimental studies were key first steps on the path to our long-term goal of this study: to bridge the current critical knowledge gap, which is the lack of understanding of the fundamental mechanisms of structure formation, initially in freeze-cast polymers, and later also in particle-based ceramic and metal systems. Knowing how the size and shape of the pores in freeze-cast materials are defined and can be controlled by controlling the ice crystal growth, the need for a better fundamental understanding of the physics of directional solidification in aqueous systems becomes even more obvious. We overcame the challenge of the absence of equilibrium phase diagrams and, even more important, the non-equilibrium state diagrams, which describe the metastable ‘states’ fundamental to an understanding of these systems; we determined concentration- and temperature-dependent diffusion coefficients and viscosities for our ternary chitosan-acetic acid-water system; and further reduced system complexity in support of the PF simulation effort by focusing our 2D and 3D studies on the binary systems trehalose-water and sucrose-water systems, for which the fundamental properties are known and documented.

Since crystal growth in bulk samples are difficult to observe and characterize in situ, diffusive crystal growth under terrestrial conditions is typically studied in 2D with thin samples. These thin samples are designed so that the solidification conditions can be controlled carefully and only a single, two-dimensional (2D) array of dendrites (or cells) forms, and the solid-liquid interface, interface dynamics, and the formation of instabilities can be observed. Initially (in Years 1-3), we focused on the traditional light microscopy perpendicular to the moving freezing front primarily in the trehalose-water and sucrose-water systems. To observe the formation of Mullins-Sekerka instabilities and their subsequent reorganization into an array of cells or dendrites as a function of polymer concentration and cooling rates (which is equal to the product of velocity and thermal gradient in directional solidification), we discovered X-ray tomoscopy, which is continuous, time-resolved tomography, as the more suitable tool for crystal growth phenomena.

With synchrotron-based tomoscopy, we have in Years 3 and 4 been able to investigate and determine the kinetics of the ice-phase growth and the mechanisms by which the growing ice crystals (thus ice phase), templates the polymer phase into a cellular solid with a range of cell wall surface features, while the polymer is increasingly upconcentrated and transitions from an aqueous solution to a glassy solid. Overall, our observation is that 2D thin film experiments should, whenever possible, be complemented by 3D in situ tomoscopy experiments, because it is impossible to extrapolate structure formation phenomena from thin film observations to bulk materials, in which the third dimension and grain or domain interactions play an important role.

As critical as 3D in situ X-ray tomoscopy has become for our study for the quantitative 3D imaging and observation also of transient events during the directional solidification in freeze-casting, are the 3D PF simulations, which started in Year 2. Remarkably, the PF simulations of anisotropic, faceted ice crystal growth binary aqueous systems with a dilute impurity (trehalose, sucrose), reproduced for the first time the various salient features of freeze-cast structures: from the cellular scaffold structure with their characteristic lamellar spacing to the cell wall surface features such as ridges, which are templated by secondary instabilities on the ice crystal’s basal plane. The value of the 3D phase-field simulations is immense, since they enable us to investigate little studied and not yet modeled mechanisms of hierarchical microstructure formation and cell wall material self-assembly, both of which define anisotropy, property profile, and overall performance of freeze-cast materials. Our results highlight the crucial role of both the solid-liquid interface free-energy and the interface kinetics in structure formation. They also highlight that other potentially important physical effects neglected in the phase-field model, such as fluid flow generated by the expansion of ice, may play a more secondary role in structure formation.

From a practical point of view, the ability to accurately predict the detailed temporal evolution of interface structures under prescribed growth conditions is critical for optimizing processing routes and material properties.

Strong, tough, and lightweight materials are needed for a myriad of structural and functional applications in Space systems and on Earth in diverse strategic fields that range from biomedical, to buildings, transportation and energy generation, or storage. These new, yet to be developed materials, should exhibit unprecedented combinations of strength and toughness, while being manufacturable at low cost and in high volume. Numerous processing techniques have been proposed to produce these materials, but frequently cannot provide the degree of microstructural control needed to manipulate and optimize the property profile, particularly of multifunctional materials. One technique, which holds great promise in fabricating novel materials with great structural control, is freeze-casting, a relatively inexpensive procedure which also provides a means to mimic complex, efficient natural materials with hierarchical designs over several length-scales. To date, the fundamental science and understanding of this processing technique is limited, because, on Earth, convection and sedimentation complicate both the interpretation of experimental results and their comparison with theoretical predications. Avoiding these in space, following four scientific goals will be pursued. To reveal on Earth (Aim 1) and in Space (Aim 2) the underlying fundamental materials science of freeze casting and establish a realistic model for structure formation in multifaceted crystal nucleation and growth. Aim 3: Develop predictive models to identify the most promising material processing combinations and conditions to optimize material performance. Aim 4: Translate the results of (1-3) into structure-property-processing correlations for highly porous, freeze-cast scaffolds (polymer, ceramic, metal, and composite) made on Earth. Data obtained and computational models will be made available to the NASA Physical Sciences Informatics to make the data accessible to the global community and help translate research into application for an accelerated pace of advanced-materials discovery, innovation, manufacture, and commercialization.

A discovery made, in Years 2-4, through 3D PF simulations is the significance of the anisotropy of the water-ice system for the initiation of formation of performance-defining features and patterns in freeze-cast materials, which consist of primary dendrites and secondary structures such as ridges or other surface side branches and might be further enhanced by interdendritic solute flow and forces resulting from the 9% volumetric expansion of water upon solidification. The value of such 3D phase-field simulations is immense, since they enable us to investigate little studied and not yet modeled mechanisms of hierarchical microstructure formation and cell wall material self-assembly, both of which define anisotropy, property profile, and overall performance of freeze-cast materials.

Strong, tough, and lightweight materials are needed for a myriad of structural and functional applications in Space systems and on Earth in diverse strategic fields that range from biomedical, to buildings, transportation and energy generation, or storage. These new, yet to be developed materials, should exhibit unprecedented combinations of strength and toughness, while being manufacturable at low cost and in high volume. Numerous processing techniques have been proposed to produce these materials, but frequently cannot provide the degree of microstructural control needed to manipulate and optimize the property profile, particularly of multifunctional materials. One technique, which holds great promise in fabricating novel materials with great structural control, is freeze-casting, a relatively inexpensive procedure which also provides a means to mimic complex, efficient natural materials with hierarchical designs over several length-scales. To date, the fundamental science and understanding of this processing technique is limited, because, on Earth, convection and sedimentation complicate both the interpretation of experimental results and their comparison with theoretical predications. Avoiding these in space, following four scientific goals will be pursued. To reveal on Earth (Aim 1) and in Space (Aim 2) the underlying fundamental materials science of freeze casting and establish a realistic model for structure formation in multifaceted crystal nucleation and growth. Aim 3: Develop predictive models to identify the most promising material processing combinations and conditions to optimize material performance. Aim 4: Translate the results of (1-3) into structure-property-processing correlations for highly porous, freeze-cast scaffolds (polymer, ceramic, metal, and composite) made on Earth. Data obtained and computational models will be made available to the NASA Physical Sciences Informatics to make the data accessible to the global community and help translate research into application for an accelerated pace of advanced-materials discovery, innovation, manufacture, and commercialization.

NOTE: Continuation of "Structure-Property-Processing Correlations in Freeze-Cast Biomimetic Materials" (grant 80NSSC18K0305 at Dartmouth College), with the same Principal Investigator, Dr. Ulrike Wegst, due to PI move to Northeastern University in summer 2020.