A combined approach of Computational Fluid Dynamic (CFD) and flow Magnetic Resonance Imaging (flo... more A combined approach of Computational Fluid Dynamic (CFD) and flow Magnetic Resonance Imaging (flow MRI) is used for a highly accurate study of flow phenomena within textiles. Preliminary simulations and experimental data demonstrate the potential of these synergistic techniques. Three-dimensional MRI techniques measure binary pixel intensities in a 3D Cartesian coordinate system. Transformation of these data measured for woven textiles in a CFD compatible computer aided design (CAD) format is feasible, however in many instances the spatial resolution of the MRI technique may not be sufficient to provide data to be used in highly accurate CFD simulations. A flow cell with conditions optimized for both techniques is in development and initial studies of (i) a phantom sample and (ii) simple woven fabrics are under preparation.
Unraveling water and salt transport in polyamide is of growing importance as the use of reverse o... more Unraveling water and salt transport in polyamide is of growing importance as the use of reverse osmosis membranes grows in many industries. Here, using solid-state nuclear magnetic resonance (NMR) spectroscopy, we measure the translational diffusion coefficients using pulsed-field gradient NMR, examine ion dynamics with NMR relaxometry, and determine activation energy barriers of hydrogen and sodium ions in ionexchanged polyamide using variable-temperature NMR. We identify two predominant diffusion components within the spectra associated with bound and unbound hydrogen and sodium ions. We show that the diffusion coefficient of the bound hydrogen ions decreases by 46% while the free hydrogen diffusion coefficient remained constant as the salinity of the mixture increases from 1 M to 2 M. Conversely, the diffusion coefficient of bounded sodium did not change while the unbounded sodium diffusion coefficient decreased by 38% as the salinity of the mixture increases from 1 M to 2 M. Through examining the spin-lattice relaxation time (T 1) at various temperatures we reveal that the sodium and hydrogen ion motion decreases with an increase in salinity, and we also report the associated activation energy. We believe these molecular-scale measurements can aid in extending the solution-diffusion model of reverse osmosis membranes.
The use of virtual prototypes for the prediction of relevant flow related parameters is well esta... more The use of virtual prototypes for the prediction of relevant flow related parameters is well established in many industries such as the automotive industry. For the development of technical textiles an analogous approach is anticipated as being beneficial. However, so far the complex geometry of textiles consisting of a very large number of filaments has impeded this approach. We utilize this approach for the first time investigating a fabric, which is used during the paper forming process. The most challenging aspect for the simulation is the the process of geometry creation by use of single filaments together with the indispensable simplifications for a currently marketed fabric. Meshes of different sizes up 20 million cells have been generated and results from CFD calculations will be displayed together with an analysis of the numerical accuracy. The individual relevance of the simulation experiments will be discussed. Physical experiments at ambient temperature of laminar water flow through the same fabric under comparable conditions with a Reynolds Number of 15 based on pipe diameter of 9.0 mm and pipe volume flow rate averaged velocity magnitude of 0.00172 m/s were performed. The Reynolds Number based on the diameter of the different filaments of 0.2 mm up to 0.45 mm is approx. between 0.34 and 0.77. The experimental set up using Magnetic Resonance Imaging (MRI) will be explained. The use of this experimental approach as a means to validate the results of the simulation will be critically evaluated.
A synergistic approach using techniques of Computational Fluid Dynamics (CFD) and Nuclear Magneti... more A synergistic approach using techniques of Computational Fluid Dynamics (CFD) and Nuclear Magnetic Resonance Imaging (MRI) is used to study textile-relevant flow phenomena on a microscopic scale. Technical textiles as used in paper producing machinery have been studied using both CFD and MRI. So far the combined approach using both methods provides a consistent picture regarding the pathway of fluid flow through these textiles. Further studies are concerned with the spontaneous imbibition of fluids in textiles (wicking), which is largely influenced by the textile micro-structure. A setup has been developed to observe the spatial and temporal fluid distribution during a wicking process by means of Magnetic Resonance Imaging. GOALS
The initial stage of the NMR 1 H T 1 relaxation of well-defined polypropylene-montmorillonite nan... more The initial stage of the NMR 1 H T 1 relaxation of well-defined polypropylene-montmorillonite nanocomposites was investigated at two different magnetic fields of 0.54 and 7.05 T. At 0.54 T, two periods can be distinguished during the first 30 ms after a saturation pulse train. Both periods scale linearly with the square root of the recovery time. The first period occurs during the first 1 ms and is attributed to direct dipolar relaxation of nuclei in immediate proximity to the clay. It is caused by paramagnetic impurities within the clay and is characterized by a magnetization recovery curve with a slope proportional to the concentration of these impurities. The second period occurs at 4 to 30 ms after saturation and is due to spin diffusion between the sink, formed by the initial relaxation at the clay surface, and the surrounding polymer matrix, which relaxes at a much slower rate. The second period is characterized by a magnetization recovery curve with a slope proportional to the effective surface area of the clay, from which a degree of exfoliation may be determined. At 7.05 T, only a single relaxation recovery period is observed. At this higher magnetic field, the direct relaxation is characterized by a substantially longer relaxation time so that it is not distinguished from the spin-diffusion process. As with the slope of the second period of the magnetization recovery at 0.54 T, the slope of the magnetization recovery curve at 7.05 T can be utilized to extract a degree of exfoliation.
1 H NMR relaxation data provide insight into the effects of carbon black fillers on the structure... more 1 H NMR relaxation data provide insight into the effects of carbon black fillers on the structure of polymer networks in products based on natural rubber so that accepted ideas concerning the interaction between elastomeric networks and active filling materials are confirmed. A new 1 H NMR relaxation experiment allows the direct investigation of dangling chains within the polymeric network. In samples containing carbon black a motional anisotropy is observed for these chain ends, while dangling chains in samples without carbon black fillers show isotropic rotational motions. The parameter q , quantifying the motional anisotropy, is suggested to be a measure of the physico-chemical interactions between elastomer and filler.
PROJECT GOALS: To understand and quantify moisture transport in textile structures so that novel/... more PROJECT GOALS: To understand and quantify moisture transport in textile structures so that novel/improved materials for fluid management and novel/improved drying processes may be developed. Magnetic resonance imaging (MRI) and other techniques are being used to investigate moisture transport in textiles. MRI revealed that moisture distribution in carpet is significantly influenced by the vacuum extraction procedure. Industrially relevant through-flow drying of carpet has been simulated on a laboratory through-flow dryer (LTFD) as well as inside a MRI scanner. The effects of the moisture distribution and the air flow direction on through-flow drying of unbacked tufted carpet are being studied. Methods to achieve faster drying via increased carpet air permeability are being developed. Based on experimental results obtained using LTFD, the potential to improve drying in constant rate and falling rate drying periods is being explored. Anisotropic wicking of fabrics is being studied. Tw...
Carbon molecular sieve (CMS) membranes have impressive separation properties; however, both chemi... more Carbon molecular sieve (CMS) membranes have impressive separation properties; however, both chemical and morphology structures need to be understood better. Here we characterize CMS with the simplest polyimide (PI) PMDA/pPDA (PMDA=Pyromellitic Dianhydride, pPDA= p -Phenylenediamine), using FTIR, solid state 15 N-NMR, 13 C-NMR, XPS, XRD, and Raman spectra to study chemical structure. We also compare gas separation properties for this CMS to a CMS derived from a more conventional polyimide precursor. The detailed characterization shows the presence of aromatic pyridinic, pyrrolic rings as well as graphitic, pyridonic components and a few other groups in both CMS types derived from the very different precursors. The CMS morphologies, while related to precursor and pyrolysis temperature details, show similarities consistent with a physical picture comprising distributed molecular sieving plate-like structures. These results assist in understanding diverse CMS membrane separation performance.
To examine multi‐component relaxation modelling for quantification of on‐ and off‐resonance relax... more To examine multi‐component relaxation modelling for quantification of on‐ and off‐resonance relaxation signals in multi‐echo ultra‐short echo time (UTE) data of human Achilles tendon (AT) and compare bias and dispersion errors of model parameters to that of the bi‐component model.
liquid electrolytes. [2] Solid state electrolytes (SSE) promise to overcome some of such concerns... more liquid electrolytes. [2] Solid state electrolytes (SSE) promise to overcome some of such concerns and offer dramatically reduced flammability and temperature stability, [6] reduced toxicity, and the compatibility with high capacity Li/Li alloy anodes and high-voltage cathodes. [7] Even though the conductivity of some of the SSEs can be as high as 0.01 S cm −1 , high-energy density solid-state batteries still face many challenges, such as: 1) high interfacial resistance at the SSE-electrode interfaces, 2) difficulties producing robust thin SSE membranes, and 3) high electrolyte synthesis and solid battery fabrication costs. [8] Many of these issues stem from the intrinsically high processing temperatures for nearly all common SSE materials, which often exceed 800-1000 °C. [9] Lithium hydroxychloride (Li 2 OHCl), a derivative of Li 3 OCl, provides a lowmelting-point (<300 °C) compared to other types of inorganic SSEs. Li-antiperovskite Li 2 OHCl results from the substitution of one of Li atom with one H atom in Li 3 OCl. It exhibits many attractive properties, including low melting points, low cost of Li precursors, and easy processing. [10] While Li 2 OHCl has a similar crystal structure to Li 3 OCl, Li vacancies and OH groups are present in Li 2 OHCl. [11] The OH groups in Li 2 OHCl is believed to boost Li-ion motion based on the recently published the molecular dynamic (MD) simulations. [12,13] Unfortunately, it is challenging to validate the mechanism of Li-ion transport in this compound with existing experimental data and by means Low-melting-point solid-state electrolytes (SSE) are critically important for low-cost manufacturing of all-solid-state batteries. Lithium hydroxychloride (Li 2 OHCl) is a promising material within the SSE domain due to its low melting point (mp < 300 °C), cheap ingredients (Li, H, O, and Cl), and rapid synthesis. Another unique feature of this compound is the presence of Li vacancies and rotating hydroxyl groups which promote Li-ion diffusion, yet the role of the protons in the ion transport remains poorly understood. To examine lithium and proton dynamics, a set of solid-state NMR experiments are conducted, such as magic-angle spinning 7 Li NMR, static 7 Li and 1 H NMR, and spin-lattice T 1 (7 Li)/T 1 (1 H) relaxation experiments. It is determined that only Li + contributes to long-range ion transport, while H + dynamics is constrained to an incomplete isotropic rotation of the OH group. The results uncover detailed mechanistic understanding of the ion transport in Li 2 OHCl. It is shown that two distinct phases of ionic motions appear at low and elevated temperatures, and that the rotation of the OH group controls Li + and H + dynamics in both phases. The model based on the NMR experiments is fully consistent with crystallographic information, ionic conductivity measurements, and Born-Oppenheimer molecular dynamic simulations.
PbI 4 (4NPEA = 4-nitrophenylethylammonium) is the first 3 × 3 corrugated 2D organic-Pb/I perovski... more PbI 4 (4NPEA = 4-nitrophenylethylammonium) is the first 3 × 3 corrugated 2D organic-Pb/I perovskite. The nitro groups are involved in cation− cation and cation-iodide interactions. The structure contains both highly distorted and near-ideal PbI 6 octahedra, consistent with the observation of two 207 Pb NMR resonances, while the optical properties resemble those of other 2D perovskites with distorted PbI 6 octahedra.
PIM-1, a solution-processable, permanently microporous polymer has been demonstrated as a viable ... more PIM-1, a solution-processable, permanently microporous polymer has been demonstrated as a viable support material for PEI, the benchmark aminopolymer used for CO 2 capture. Significance and Impact PIM-1 has the ability to be processed into novel geometries for CO 2 capture contactors (such as hollow fibers and others), thus allowing for major gains in energy efficiency of adsorption systems relative to traditional pellet-based systems due to improved heat mass management, lower pressure drops and more rapid mass transport.
The adsorption and diffusion of alcohol and hydrocarbon vapors in ZIF-11 are reported as a functi... more The adsorption and diffusion of alcohol and hydrocarbon vapors in ZIF-11 are reported as a function of loading at 308 K. The hydrophobicity of the benzimidazole linkers provides moderate IAST selectivities for adsorptive alcohol/water separations until high relative humidity conditions. Sorbates well beyond the crystallographic pore aperture are admitted into the framework at decreasing diffusivities with increasing molecular size. The diffusion of methane is also probed as a function of temperature, revealing a non-constant activation energy of diffusion, which is linked to the temperature-dependent flexibility of the ligands comprising the six-and eight-membered aperture rings as revealed through solid state NMR. Compared to ZIF-8, ZIF-11 surprisingly demonstrates higher diffusivities and lower activation energies despite the smaller crystallographic aperture size. This phenomenon is explained via molecular dynamics simulations that highlight the greater flexibility of the benzimidazole linker in ZIF-11 relative to the 2-methylimidazolate linker in ZIF-8 and emphasizes the importance of structural flexibility in identifying diffusionallyselective materials.
Effective drug delivery in brain tumors remains a major challenge in oncology. Although local hyp... more Effective drug delivery in brain tumors remains a major challenge in oncology. Although local hyperthermia and stimuli-responsive delivery systems, such as thermosensitive liposomes, represent promising strategies to locally enhance drug delivery in solid tumors and improve outcomes, their application in intracranial malignancies remains unexplored. We hypothesized that the combined abilities of closed-loop trans-skull Magnetic Resonance Imaging guided Focused Ultrasound (MRgFUS) hyperthermia with those of thermosensitive drugs can alleviate challenges in drug delivery and improve survival in gliomas. Methods: To conduct our investigations, we first designed a closed loop MR-guided Focused Ultrasound (MRgFUS) system for localized trans-skull hyperthermia (ΔT < 0.5 °C) in rodents and established safety thresholds in healthy mice. To assess the abilities of the developed system and proposed therapeutic strategy for FUS-triggered chemotherapy release we employed thermosensitive liposomal Dox (TSL-Dox) and tested it in two different glioma tumor models (F98 in rats and GL261 in mice). To quantify Dox delivery and changes in the transvascular transport dynamics in the tumor microenvironment we combined fluorescent microscopy, dynamic contrast enhanced MRI (DCE-MRI), and physiologically based pharmacokinetic (PBPK) modeling. Lastly, to assess the therapeutic efficacy of the system and of the proposed therapeutic strategy we performed a survival study in the GL261 glioma bearing mice. Results: The developed closed-loop trans-skull MRgFUS-hyperthermia system that operated at 1.7 MHz, a frequency that maximized the brain (FUS-focus) to skull temperature ratio in mice, was able to attain and maintain the desired focal temperature within a narrow range. Histological evidence (H&E and Nissl) suggests that focal temperature at 41.5 ± 0.5 °C for 10 min is below the threshold for tissue damage. Quantitative analysis of doxorubicin delivery from TSLs with MRgFUS-hyperthermia demonstrated 3.5-fold improvement in cellular uptake in GL261 glioma mouse tumors (p < 0.001) and 5-fold increase in delivery in F98 glioma rat tumors (p < 0.05), as compared to controls (TSL-Dox-only). Moreover, PBPK modeling of drug transport that was calibrated using the experimental data indicated that thermal stress could lead to significant improvement in the transvascular transport (2.3-fold increase in the vessel diffusion coefficient; P < 0.001), in addition to promoting targeted Dox release. Prospective experimental investigations with DCE-MRI during FUS-hyperthermia, supported these findings and provided evidence that moderate thermal stress (≈41 °C for up to 10 min) can promote acute changes in the vascular transport dynamics in the brain tumor microenvironment (Ktrans value for control vs. FUS was 0.0097 and 0.0148 min-1, respectively; p = 0.026). Crucially, survival analysis demonstrated significant improvement in the survival in the TSL-Dox-FUS group as compared to TSL-Dox-only group (p < 0.05), providing supporting evidence on the therapeutic potential of the proposed strategy. Conclusions: Our investigations demonstrated that spatially controlled thermal stress can be attained and sustained in the mouse brain, using a trans-skull closed-loop MRgFUS system, and used to promote the effective delivery of chemotherapy in gliomas from thermosensitive drugs. This system also allowed us to conduct mechanistic investigations that resulted in the refinement of our understanding on the role of thermal stress in augmenting mass and drug transport in brain tumors. Overall, our study established a new paradigm for effective drug delivery in brain tumors based on closed-loop ultrasound-mediated thermal stress and thermosensitive drugs.
Here we report that a covalent organic framework (COF), which contains 2,5-di(imine)-substituted ... more Here we report that a covalent organic framework (COF), which contains 2,5-di(imine)-substituted 1,4-dihydroxybenzene (diiminol) moieties, undergoes color changes in the presence of solvents or solvent vapor that are rapid, passive, reversible, and easily detectable by the naked eye. A new visible absorption band appears in the presence of polar solvents, especially water, suggesting reversible conversion to another species. This reversibility is attributed to the ability of the diiminol to rapidly tautomerize to an iminol/cis-ketoenamine and its inability to doubly tautomerize to a diketoenamine. Density functional theory (DFT) calculations suggest similar energies for the two tautomers in the presence of water, but the diiminol is much more stable in its absence. Time-dependent DFT calculations confirm that the iminol/cis-ketoenamine absorbs at longer wavelength than the diiminol and indicate that this absorption has significant charge-transfer character. A colorimetric humidity sensing device constructed from an oriented thin film of the COF responded quickly to water vapor and was stable for months. These results suggest that tautomerization-induced electronic structure changes can be exploited in COF platforms to give rapid, reversible sensing in systems that exhibit long-term stability.
We have synthesized low-molecular-weight diblock copolymers of polystyrene-block-poly(dimethylsil... more We have synthesized low-molecular-weight diblock copolymers of polystyrene-block-poly(dimethylsiloxane) with total molecular weights <12 kg/mol and PS volume fractions of w0.2. We have investigated the phase behavior of the PS-PDMS in its pure state and with up to 10 wt% of C 60 added. The C 60 was shown to selectively segregate into the PS phase only although its solubility limit is w1 wt%. Although the C 60 aggregates above 1 wt%, the cylindrical morphology observed in the pure copolymer bulk samples persists in the C 60 -copolymer composites even up to 10 wt% C 60 loading. In thin films, the pure copolymer possesses a highly ordered morphology with grains hundreds of microns across. When C 60 is blended with the copolymer the high degree of order rapidly decreases due to increasing numbers of defects observed.
This paper introduces two experimental studies of capillary impregnation across fiber tows. The f... more This paper introduces two experimental studies of capillary impregnation across fiber tows. The first experimental technique embeds four to five flow detection sensors into a fiber tow at radial locations from the outside to the center of the tow to track the motion of fluid from outside to the center of the tow with time. The second technique based on Magnetic Resonance Imaging (MRI) is a non-intrusive tracking of the flow front as it impregnates the fiber tow. The techniques are compared and contrasted to identify their advantages and limitations. An analytical model that ignores the backpressure of the entrapped air grossly under predicts the saturation time for the tow as compared with the experiments. In order to explain this discrepancy, we include the effect of entrapped air in the analytic model, which slows down the capillary flow. However, other effects such as non-uniform fiber volume fraction within the tow and the ease with which the entrapped air can escape from the to...
A combined approach of Computational Fluid Dynamic (CFD) and flow Magnetic Resonance Imaging (flo... more A combined approach of Computational Fluid Dynamic (CFD) and flow Magnetic Resonance Imaging (flow MRI) is used for a highly accurate study of flow phenomena within textiles. Preliminary simulations and experimental data demonstrate the potential of these synergistic techniques. Three-dimensional MRI techniques measure binary pixel intensities in a 3D Cartesian coordinate system. Transformation of these data measured for woven textiles in a CFD compatible computer aided design (CAD) format is feasible, however in many instances the spatial resolution of the MRI technique may not be sufficient to provide data to be used in highly accurate CFD simulations. A flow cell with conditions optimized for both techniques is in development and initial studies of (i) a phantom sample and (ii) simple woven fabrics are under preparation.
Unraveling water and salt transport in polyamide is of growing importance as the use of reverse o... more Unraveling water and salt transport in polyamide is of growing importance as the use of reverse osmosis membranes grows in many industries. Here, using solid-state nuclear magnetic resonance (NMR) spectroscopy, we measure the translational diffusion coefficients using pulsed-field gradient NMR, examine ion dynamics with NMR relaxometry, and determine activation energy barriers of hydrogen and sodium ions in ionexchanged polyamide using variable-temperature NMR. We identify two predominant diffusion components within the spectra associated with bound and unbound hydrogen and sodium ions. We show that the diffusion coefficient of the bound hydrogen ions decreases by 46% while the free hydrogen diffusion coefficient remained constant as the salinity of the mixture increases from 1 M to 2 M. Conversely, the diffusion coefficient of bounded sodium did not change while the unbounded sodium diffusion coefficient decreased by 38% as the salinity of the mixture increases from 1 M to 2 M. Through examining the spin-lattice relaxation time (T 1) at various temperatures we reveal that the sodium and hydrogen ion motion decreases with an increase in salinity, and we also report the associated activation energy. We believe these molecular-scale measurements can aid in extending the solution-diffusion model of reverse osmosis membranes.
The use of virtual prototypes for the prediction of relevant flow related parameters is well esta... more The use of virtual prototypes for the prediction of relevant flow related parameters is well established in many industries such as the automotive industry. For the development of technical textiles an analogous approach is anticipated as being beneficial. However, so far the complex geometry of textiles consisting of a very large number of filaments has impeded this approach. We utilize this approach for the first time investigating a fabric, which is used during the paper forming process. The most challenging aspect for the simulation is the the process of geometry creation by use of single filaments together with the indispensable simplifications for a currently marketed fabric. Meshes of different sizes up 20 million cells have been generated and results from CFD calculations will be displayed together with an analysis of the numerical accuracy. The individual relevance of the simulation experiments will be discussed. Physical experiments at ambient temperature of laminar water flow through the same fabric under comparable conditions with a Reynolds Number of 15 based on pipe diameter of 9.0 mm and pipe volume flow rate averaged velocity magnitude of 0.00172 m/s were performed. The Reynolds Number based on the diameter of the different filaments of 0.2 mm up to 0.45 mm is approx. between 0.34 and 0.77. The experimental set up using Magnetic Resonance Imaging (MRI) will be explained. The use of this experimental approach as a means to validate the results of the simulation will be critically evaluated.
A synergistic approach using techniques of Computational Fluid Dynamics (CFD) and Nuclear Magneti... more A synergistic approach using techniques of Computational Fluid Dynamics (CFD) and Nuclear Magnetic Resonance Imaging (MRI) is used to study textile-relevant flow phenomena on a microscopic scale. Technical textiles as used in paper producing machinery have been studied using both CFD and MRI. So far the combined approach using both methods provides a consistent picture regarding the pathway of fluid flow through these textiles. Further studies are concerned with the spontaneous imbibition of fluids in textiles (wicking), which is largely influenced by the textile micro-structure. A setup has been developed to observe the spatial and temporal fluid distribution during a wicking process by means of Magnetic Resonance Imaging. GOALS
The initial stage of the NMR 1 H T 1 relaxation of well-defined polypropylene-montmorillonite nan... more The initial stage of the NMR 1 H T 1 relaxation of well-defined polypropylene-montmorillonite nanocomposites was investigated at two different magnetic fields of 0.54 and 7.05 T. At 0.54 T, two periods can be distinguished during the first 30 ms after a saturation pulse train. Both periods scale linearly with the square root of the recovery time. The first period occurs during the first 1 ms and is attributed to direct dipolar relaxation of nuclei in immediate proximity to the clay. It is caused by paramagnetic impurities within the clay and is characterized by a magnetization recovery curve with a slope proportional to the concentration of these impurities. The second period occurs at 4 to 30 ms after saturation and is due to spin diffusion between the sink, formed by the initial relaxation at the clay surface, and the surrounding polymer matrix, which relaxes at a much slower rate. The second period is characterized by a magnetization recovery curve with a slope proportional to the effective surface area of the clay, from which a degree of exfoliation may be determined. At 7.05 T, only a single relaxation recovery period is observed. At this higher magnetic field, the direct relaxation is characterized by a substantially longer relaxation time so that it is not distinguished from the spin-diffusion process. As with the slope of the second period of the magnetization recovery at 0.54 T, the slope of the magnetization recovery curve at 7.05 T can be utilized to extract a degree of exfoliation.
1 H NMR relaxation data provide insight into the effects of carbon black fillers on the structure... more 1 H NMR relaxation data provide insight into the effects of carbon black fillers on the structure of polymer networks in products based on natural rubber so that accepted ideas concerning the interaction between elastomeric networks and active filling materials are confirmed. A new 1 H NMR relaxation experiment allows the direct investigation of dangling chains within the polymeric network. In samples containing carbon black a motional anisotropy is observed for these chain ends, while dangling chains in samples without carbon black fillers show isotropic rotational motions. The parameter q , quantifying the motional anisotropy, is suggested to be a measure of the physico-chemical interactions between elastomer and filler.
PROJECT GOALS: To understand and quantify moisture transport in textile structures so that novel/... more PROJECT GOALS: To understand and quantify moisture transport in textile structures so that novel/improved materials for fluid management and novel/improved drying processes may be developed. Magnetic resonance imaging (MRI) and other techniques are being used to investigate moisture transport in textiles. MRI revealed that moisture distribution in carpet is significantly influenced by the vacuum extraction procedure. Industrially relevant through-flow drying of carpet has been simulated on a laboratory through-flow dryer (LTFD) as well as inside a MRI scanner. The effects of the moisture distribution and the air flow direction on through-flow drying of unbacked tufted carpet are being studied. Methods to achieve faster drying via increased carpet air permeability are being developed. Based on experimental results obtained using LTFD, the potential to improve drying in constant rate and falling rate drying periods is being explored. Anisotropic wicking of fabrics is being studied. Tw...
Carbon molecular sieve (CMS) membranes have impressive separation properties; however, both chemi... more Carbon molecular sieve (CMS) membranes have impressive separation properties; however, both chemical and morphology structures need to be understood better. Here we characterize CMS with the simplest polyimide (PI) PMDA/pPDA (PMDA=Pyromellitic Dianhydride, pPDA= p -Phenylenediamine), using FTIR, solid state 15 N-NMR, 13 C-NMR, XPS, XRD, and Raman spectra to study chemical structure. We also compare gas separation properties for this CMS to a CMS derived from a more conventional polyimide precursor. The detailed characterization shows the presence of aromatic pyridinic, pyrrolic rings as well as graphitic, pyridonic components and a few other groups in both CMS types derived from the very different precursors. The CMS morphologies, while related to precursor and pyrolysis temperature details, show similarities consistent with a physical picture comprising distributed molecular sieving plate-like structures. These results assist in understanding diverse CMS membrane separation performance.
To examine multi‐component relaxation modelling for quantification of on‐ and off‐resonance relax... more To examine multi‐component relaxation modelling for quantification of on‐ and off‐resonance relaxation signals in multi‐echo ultra‐short echo time (UTE) data of human Achilles tendon (AT) and compare bias and dispersion errors of model parameters to that of the bi‐component model.
liquid electrolytes. [2] Solid state electrolytes (SSE) promise to overcome some of such concerns... more liquid electrolytes. [2] Solid state electrolytes (SSE) promise to overcome some of such concerns and offer dramatically reduced flammability and temperature stability, [6] reduced toxicity, and the compatibility with high capacity Li/Li alloy anodes and high-voltage cathodes. [7] Even though the conductivity of some of the SSEs can be as high as 0.01 S cm −1 , high-energy density solid-state batteries still face many challenges, such as: 1) high interfacial resistance at the SSE-electrode interfaces, 2) difficulties producing robust thin SSE membranes, and 3) high electrolyte synthesis and solid battery fabrication costs. [8] Many of these issues stem from the intrinsically high processing temperatures for nearly all common SSE materials, which often exceed 800-1000 °C. [9] Lithium hydroxychloride (Li 2 OHCl), a derivative of Li 3 OCl, provides a lowmelting-point (<300 °C) compared to other types of inorganic SSEs. Li-antiperovskite Li 2 OHCl results from the substitution of one of Li atom with one H atom in Li 3 OCl. It exhibits many attractive properties, including low melting points, low cost of Li precursors, and easy processing. [10] While Li 2 OHCl has a similar crystal structure to Li 3 OCl, Li vacancies and OH groups are present in Li 2 OHCl. [11] The OH groups in Li 2 OHCl is believed to boost Li-ion motion based on the recently published the molecular dynamic (MD) simulations. [12,13] Unfortunately, it is challenging to validate the mechanism of Li-ion transport in this compound with existing experimental data and by means Low-melting-point solid-state electrolytes (SSE) are critically important for low-cost manufacturing of all-solid-state batteries. Lithium hydroxychloride (Li 2 OHCl) is a promising material within the SSE domain due to its low melting point (mp < 300 °C), cheap ingredients (Li, H, O, and Cl), and rapid synthesis. Another unique feature of this compound is the presence of Li vacancies and rotating hydroxyl groups which promote Li-ion diffusion, yet the role of the protons in the ion transport remains poorly understood. To examine lithium and proton dynamics, a set of solid-state NMR experiments are conducted, such as magic-angle spinning 7 Li NMR, static 7 Li and 1 H NMR, and spin-lattice T 1 (7 Li)/T 1 (1 H) relaxation experiments. It is determined that only Li + contributes to long-range ion transport, while H + dynamics is constrained to an incomplete isotropic rotation of the OH group. The results uncover detailed mechanistic understanding of the ion transport in Li 2 OHCl. It is shown that two distinct phases of ionic motions appear at low and elevated temperatures, and that the rotation of the OH group controls Li + and H + dynamics in both phases. The model based on the NMR experiments is fully consistent with crystallographic information, ionic conductivity measurements, and Born-Oppenheimer molecular dynamic simulations.
PbI 4 (4NPEA = 4-nitrophenylethylammonium) is the first 3 × 3 corrugated 2D organic-Pb/I perovski... more PbI 4 (4NPEA = 4-nitrophenylethylammonium) is the first 3 × 3 corrugated 2D organic-Pb/I perovskite. The nitro groups are involved in cation− cation and cation-iodide interactions. The structure contains both highly distorted and near-ideal PbI 6 octahedra, consistent with the observation of two 207 Pb NMR resonances, while the optical properties resemble those of other 2D perovskites with distorted PbI 6 octahedra.
PIM-1, a solution-processable, permanently microporous polymer has been demonstrated as a viable ... more PIM-1, a solution-processable, permanently microporous polymer has been demonstrated as a viable support material for PEI, the benchmark aminopolymer used for CO 2 capture. Significance and Impact PIM-1 has the ability to be processed into novel geometries for CO 2 capture contactors (such as hollow fibers and others), thus allowing for major gains in energy efficiency of adsorption systems relative to traditional pellet-based systems due to improved heat mass management, lower pressure drops and more rapid mass transport.
The adsorption and diffusion of alcohol and hydrocarbon vapors in ZIF-11 are reported as a functi... more The adsorption and diffusion of alcohol and hydrocarbon vapors in ZIF-11 are reported as a function of loading at 308 K. The hydrophobicity of the benzimidazole linkers provides moderate IAST selectivities for adsorptive alcohol/water separations until high relative humidity conditions. Sorbates well beyond the crystallographic pore aperture are admitted into the framework at decreasing diffusivities with increasing molecular size. The diffusion of methane is also probed as a function of temperature, revealing a non-constant activation energy of diffusion, which is linked to the temperature-dependent flexibility of the ligands comprising the six-and eight-membered aperture rings as revealed through solid state NMR. Compared to ZIF-8, ZIF-11 surprisingly demonstrates higher diffusivities and lower activation energies despite the smaller crystallographic aperture size. This phenomenon is explained via molecular dynamics simulations that highlight the greater flexibility of the benzimidazole linker in ZIF-11 relative to the 2-methylimidazolate linker in ZIF-8 and emphasizes the importance of structural flexibility in identifying diffusionallyselective materials.
Effective drug delivery in brain tumors remains a major challenge in oncology. Although local hyp... more Effective drug delivery in brain tumors remains a major challenge in oncology. Although local hyperthermia and stimuli-responsive delivery systems, such as thermosensitive liposomes, represent promising strategies to locally enhance drug delivery in solid tumors and improve outcomes, their application in intracranial malignancies remains unexplored. We hypothesized that the combined abilities of closed-loop trans-skull Magnetic Resonance Imaging guided Focused Ultrasound (MRgFUS) hyperthermia with those of thermosensitive drugs can alleviate challenges in drug delivery and improve survival in gliomas. Methods: To conduct our investigations, we first designed a closed loop MR-guided Focused Ultrasound (MRgFUS) system for localized trans-skull hyperthermia (ΔT < 0.5 °C) in rodents and established safety thresholds in healthy mice. To assess the abilities of the developed system and proposed therapeutic strategy for FUS-triggered chemotherapy release we employed thermosensitive liposomal Dox (TSL-Dox) and tested it in two different glioma tumor models (F98 in rats and GL261 in mice). To quantify Dox delivery and changes in the transvascular transport dynamics in the tumor microenvironment we combined fluorescent microscopy, dynamic contrast enhanced MRI (DCE-MRI), and physiologically based pharmacokinetic (PBPK) modeling. Lastly, to assess the therapeutic efficacy of the system and of the proposed therapeutic strategy we performed a survival study in the GL261 glioma bearing mice. Results: The developed closed-loop trans-skull MRgFUS-hyperthermia system that operated at 1.7 MHz, a frequency that maximized the brain (FUS-focus) to skull temperature ratio in mice, was able to attain and maintain the desired focal temperature within a narrow range. Histological evidence (H&E and Nissl) suggests that focal temperature at 41.5 ± 0.5 °C for 10 min is below the threshold for tissue damage. Quantitative analysis of doxorubicin delivery from TSLs with MRgFUS-hyperthermia demonstrated 3.5-fold improvement in cellular uptake in GL261 glioma mouse tumors (p < 0.001) and 5-fold increase in delivery in F98 glioma rat tumors (p < 0.05), as compared to controls (TSL-Dox-only). Moreover, PBPK modeling of drug transport that was calibrated using the experimental data indicated that thermal stress could lead to significant improvement in the transvascular transport (2.3-fold increase in the vessel diffusion coefficient; P < 0.001), in addition to promoting targeted Dox release. Prospective experimental investigations with DCE-MRI during FUS-hyperthermia, supported these findings and provided evidence that moderate thermal stress (≈41 °C for up to 10 min) can promote acute changes in the vascular transport dynamics in the brain tumor microenvironment (Ktrans value for control vs. FUS was 0.0097 and 0.0148 min-1, respectively; p = 0.026). Crucially, survival analysis demonstrated significant improvement in the survival in the TSL-Dox-FUS group as compared to TSL-Dox-only group (p < 0.05), providing supporting evidence on the therapeutic potential of the proposed strategy. Conclusions: Our investigations demonstrated that spatially controlled thermal stress can be attained and sustained in the mouse brain, using a trans-skull closed-loop MRgFUS system, and used to promote the effective delivery of chemotherapy in gliomas from thermosensitive drugs. This system also allowed us to conduct mechanistic investigations that resulted in the refinement of our understanding on the role of thermal stress in augmenting mass and drug transport in brain tumors. Overall, our study established a new paradigm for effective drug delivery in brain tumors based on closed-loop ultrasound-mediated thermal stress and thermosensitive drugs.
Here we report that a covalent organic framework (COF), which contains 2,5-di(imine)-substituted ... more Here we report that a covalent organic framework (COF), which contains 2,5-di(imine)-substituted 1,4-dihydroxybenzene (diiminol) moieties, undergoes color changes in the presence of solvents or solvent vapor that are rapid, passive, reversible, and easily detectable by the naked eye. A new visible absorption band appears in the presence of polar solvents, especially water, suggesting reversible conversion to another species. This reversibility is attributed to the ability of the diiminol to rapidly tautomerize to an iminol/cis-ketoenamine and its inability to doubly tautomerize to a diketoenamine. Density functional theory (DFT) calculations suggest similar energies for the two tautomers in the presence of water, but the diiminol is much more stable in its absence. Time-dependent DFT calculations confirm that the iminol/cis-ketoenamine absorbs at longer wavelength than the diiminol and indicate that this absorption has significant charge-transfer character. A colorimetric humidity sensing device constructed from an oriented thin film of the COF responded quickly to water vapor and was stable for months. These results suggest that tautomerization-induced electronic structure changes can be exploited in COF platforms to give rapid, reversible sensing in systems that exhibit long-term stability.
We have synthesized low-molecular-weight diblock copolymers of polystyrene-block-poly(dimethylsil... more We have synthesized low-molecular-weight diblock copolymers of polystyrene-block-poly(dimethylsiloxane) with total molecular weights <12 kg/mol and PS volume fractions of w0.2. We have investigated the phase behavior of the PS-PDMS in its pure state and with up to 10 wt% of C 60 added. The C 60 was shown to selectively segregate into the PS phase only although its solubility limit is w1 wt%. Although the C 60 aggregates above 1 wt%, the cylindrical morphology observed in the pure copolymer bulk samples persists in the C 60 -copolymer composites even up to 10 wt% C 60 loading. In thin films, the pure copolymer possesses a highly ordered morphology with grains hundreds of microns across. When C 60 is blended with the copolymer the high degree of order rapidly decreases due to increasing numbers of defects observed.
This paper introduces two experimental studies of capillary impregnation across fiber tows. The f... more This paper introduces two experimental studies of capillary impregnation across fiber tows. The first experimental technique embeds four to five flow detection sensors into a fiber tow at radial locations from the outside to the center of the tow to track the motion of fluid from outside to the center of the tow with time. The second technique based on Magnetic Resonance Imaging (MRI) is a non-intrusive tracking of the flow front as it impregnates the fiber tow. The techniques are compared and contrasted to identify their advantages and limitations. An analytical model that ignores the backpressure of the entrapped air grossly under predicts the saturation time for the tow as compared with the experiments. In order to explain this discrepancy, we include the effect of entrapped air in the analytic model, which slows down the capillary flow. However, other effects such as non-uniform fiber volume fraction within the tow and the ease with which the entrapped air can escape from the to...
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Papers by Johannes Leisen