Physics-based void nucleation model using discrete dislocation dynamics and cluster dynamics models

Focusing on cavity nucleation, continuum damage mechanics models rely on a posteriori calibration of initial site density and loading conditions. However, empirically calibrated parameters are unreliable due to accelerated testing conditions and cannot be transferred to novel materials. To provide a more accurate description of the relationship between temperature, stress, microstructure, and the kinetics of void nucleation, we develop a physically-based nucleation model by coupling discrete dislocation dynamics (DDD) and cluster dynamics (CD) models. First, a continuum statistical approach developed for this study is shown, demonstrating the ability to model vacancies cluster size evolution as a function of time. Second, the implementation of the DDD method in the study of local energetics within a microstructure is presented. DDD has the capability to accurately model complex dislocation networks permitting a high-fidelity account of the local energy landscape arising from defect-defect interactions. Lastly, multiple potential nucleation sites in bulk are examined for nucleation. Our results are consistent with experimental observations indicating that nucleation is highly improbable in bulk

Effect of surface morphologies and chemistry of paper on deposited collagen

Paper-based platforms for biological studies have received significant attention given that cellulose is ubiquitous, biocompatible, and can be readily organized into tunable fibrous structures. In the latter form, effect of complexity in surface morphologies (roughness, porosity and fiber organization) on cell-substrate interaction has not been thoroughly explored. We infer that altering the properties of a fibrous material should lead to significant changes in cellular microenvironment and direct the deposition of structurally analogous extracellular matrix (fiber-fiber templating) like collagen. Here, we elucidate the effect of varying paper roughness and surface chemistry on NIH/3T3 fibroblasts via organization of excreted collagen. Collagen intensity was found to increase linearly with paper porosity, indicating a 3D culture platform. The intensity, however, decays over time due to biodegradation of the substrate. Stability can be improved by introducing fluorinated alkyl silanes to yield hydrophobic paper. This process concomitantly transforms the substrate to a 2D-like scaffold where collagen is predominantly assembled on the surface, thus changing the cellular microenvironment. Altering surface energy also led to fluctuations in collagen intensity and organization over time for smooth (calendered) paper substrates. We infer that the increased roughness improves collagen adsorption through capillary driven petal effect. In general, the influence of the substrate simultaneously affects its ability to host collagen and guide orientation. These findings offer insights into the effects of secondary structures and chemistry of fibrous polymeric materials on cell culture, which we propose as vital parameters when using paper-based platforms

Physics-based void nucleation model using discrete dislocation dynamics and cluster dynamics models

Focusing on cavity nucleation, continuum damage mechanics models rely on a posteriori calibration of initial site density and loading conditions. However, empirically calibrated parameters are unreliable due to accelerated testing conditions and cannot be transferred to novel materials. To provide a more accurate description of the relationship between temperature, stress, microstructure, and the kinetics of void nucleation, we develop a physically-based nucleation model by coupling discrete dislocation dynamics (DDD) and cluster dynamics (CD) models. First, a continuum statistical approach developed for this study is shown, demonstrating the ability to model vacancies cluster size evolution as a function of time. Second, the implementation of the DDD method in the study of local energetics within a microstructure is presented. DDD has the capability to accurately model complex dislocation networks permitting a high-fidelity account of the local energy landscape arising from defect-defect interactions. Lastly, multiple potential nucleation sites in bulk are examined for nucleation. Our results are consistent with experimental observations indicating that nucleation is highly improbable in bulk

Effect of surface morphologies and chemistry of paper on deposited collagen

International audienc

Effect of surface morphologies and chemistry of paper on deposited collagen

Paper-based platforms for biological studies have received significant attention given that cellulose is ubiquitous, biocompatible, and can be readily organized into tunable fibrous structures. In the latter form, effect of complexity in surface morphologies (roughness, porosity and fiber organization) on cell-substrate interaction has not been thoroughly explored. We infer that altering the properties of a fibrous material should lead to significant changes in cellular microenvironment and direct the deposition of structurally analogous extracellular matrix (fiber-fiber templating) like collagen. Here, we elucidate the effect of varying paper roughness and surface chemistry on NIH/3T3 fibroblasts via organization of excreted collagen. Collagen intensity was found to increase linearly with paper porosity, indicating a 3D culture platform. The intensity, however, decays over time due to biodegradation of the substrate. Stability can be improved by introducing fluorinated alkyl silanes to yield hydrophobic paper. This process concomitantly transforms the substrate to a 2D-like scaffold where collagen is predominantly assembled on the surface, thus changing the cellular microenvironment. Altering surface energy also led to fluctuations in collagen intensity and organization over time for smooth (calendered) paper substrates. We infer that the increased roughness improves collagen adsorption through capillary driven petal effect. In general, the influence of the substrate simultaneously affects its ability to host collagen and guide orientation. These findings offer insights into the effects of secondary structures and chemistry of fibrous polymeric materials on cell culture, which we propose as vital parameters when using paper-based platforms.This is a manuscript of an article published as Chang, Boyce S., Anuraag Boddupalli, Andrea F. Boyer, Millicent Orondo, Jean-Francis Bloch, Kaitlin M. Bratlie, and Martin M. Thuo. "Effect of surface morphologies and chemistry of paper on deposited collagen." Applied Surface Science 484 (2019): 461-469. DOI: 10.1016/j.apsusc.2019.04.131. Posted with permission.</p