Arthur Schlothauer


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Schlothauer

First Name

Arthur

ORCID

0000-0002-7456-4816

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Publications 1 - 10 of 17
  • Designing Polymeric Materials and Processes for Novel Cardiovascular Implants
    Item type: Conference Poster
    Chen, Mary Jialu; Schlothauer, Arthur; Pappas, Georgios A.; et al. (2021)
  • Tailoring crystallinity for hemocompatible and durable PEEK cardiovascular implants
    Item type: Journal Article
    Chen, Mary Jialu; Pappas, Georgios A.; Massella, Daniele; et al. (2023)
    Biomaterials Advances
    Polymers have the potential to replace metallic or bioprosthetic heart valve components due to superior durability and inertness while allowing for native tissue-like flexibility. Despite these appealing properties, certain polymers such as polyetheretherketone (PEEK) have issues with hemocompatibility, which have previously been addressed through assorted complex processes. In this paper, we explore the enhancement of PEEK hemocompatibility with polymer crystallinity. Amorphous, semi-crystalline and crystalline PEEK are investigated in addition to a highly crystalline carbon fiber (CF)/PEEK composite material (CFPEEK). The functional group density of the PEEK samples is determined, showing that higher crystallinity results in increased amount of surface carbonyl functional groups. The increase of crystallinity (and negatively charged groups) appears to cause significant reductions in platelet adhesion (33 vs. 1.5% surface coverage), hemolysis (1.55 vs. 0.75%∙cm−2), and thrombin generation rate (4840 vs. 1585 mU/mL/min/cm2). In combination with the hemocompatibility study, mechanical characterization demonstrates that tailoring crystallinity is a simple and effective method to control both hemocompatibility and mechanical performance of PEEK. Furthermore, the results display that CFPEEK composite performed very well in all categories due to its enhanced crystallinity and complete carbon encapsulation, allowing the unique properties of CFPEEK to empower new concepts in cardiovascular device design.
  • Tailoring PEEK Crystallinity: Key For Highly Hemocompatible And Mechanically Performing Cardiovascular Implants
    Item type: Other Conference Item
    Chen, Mary Jialu; Pappas, Georgios A.; Massella, Daniele; et al. (2022)
    BACKGROUND: Polymeric transcatheter heart valves have the potential to combine the durability of mechanical heart valves with the biocompatibility of biological heart valves, resulting in devices optimized for minimally invasive surgery. However, due to their synthetic origin, polymeric materials still face issues regarding hemocompatibility. This underscores the need for the investigation of methods to improve the hemocompatibility of polymeric materials. In this research, we report on the effect of crystallinity on hemolysis, thrombogenicity, and platelet adhesion in polyetheretherketone (PEEK) surfaces, acknowledging the vast potential of PEEK on cardiovascular device design. METHODS: To improve properties of implantable cardiovascular devices, the effect of crystallinity on the hemocompatibility of PEEK surfaces is investigated. After annealing at different temperatures, the chemical composition and concentration of different functional groups is determined through Fourier-transform infrared spectroscopy (FTIR) analysis. The resulting change in hemolytic activity, thrombogenicity, and platelet adhesion is observed by standardized hemocompatibility test, alongside changes in mechanical properties such as tensile modulus and toughness. RESULTS: Higher crystallinity results in increased abundance of oxygen-containing surface functional groups. This increase of negatively charged surface functional groups causes significant reductions in the hemolysis (1.57 to 0.75% cm-2), thrombin generation rate (4840 to 1586 mU mL-1 min-1 cm-2), and platelet adhesion (31.9 to 1.5%). Further, optimized tensile toughness can be accomplished at a moderate crystallinity, with acceptable hemocompatibility indexes. CONCLUSIONS: Our results show that crystalline PEEK is highly blood compatible in all test categories. Our results also show that this increase in hemocompatibility can be accompanied by an optimization in the tensile modulus and toughness. Hence, crystallization is shown to be a simple and effective method to improve compatibility with blood and mechanical performance of PEEK used for cardiovascular implants.
  • Designing Polymeric Cardiovascular Biomaterials for Hemocompatibility and Mechanical Performance
    Item type: Conference Poster
    Chen, Mary Jialu; Pappas, Georgios A.; Massella, Daniele; et al. (2021)
    One of the greatest challenges facing polymeric cardiovascular devices is the issue of hemocompatibility. Devices such as polymeric heart valves potentially offer improved mechanical properties and quality of life compared to their animal tissue counterparts. However, they are still strongly limited by problematic interactions with blood. The reduction of platelet adhesion, thrombogenicity, and calcification have been addressed in a variety of surface and bulk modification methods, generally by increasing the hydrophilic character of polymers. However, most hydrophilization processes – oxygen plasma in particular – tend to offer limited longevity. The crystallinity of polymers has previously been observed to influence the extent of platelet adhesion, though the underlying mechanisms for this phenomenon are not clear. In this research, we report on the effect of crystallinity on hemolysis, thrombogenicity, and platelet adhesion in PEEK surfaces. By tailoring the bulk crystallinity, we demonstrate changes in the surface chemical composition and propose a potential strategy to achieve longer term surface modification for improved hemocompatibility. Additionally, we explore the influence of crystallinity on the mechanical properties of thin PEEK films, establishing the multi-dimensional impact of polymer crystallinity. The results shown here may have implications for the design of polymeric cardiovascular devices and considerations that should be taken during material selection.
  • Material response and failure of highly deformable carbon fiber composite shells
    Item type: Journal Article
    Schlothauer, Arthur; Pappas, Georgios A.; Ermanni, Paolo (2020)
    Composites Science and Technology
    Very thin carbon fiber composite shells can withstand large bending curvatures without failure. The resulting high tensile and compressive strains require accurate modeling of the fiber-dominated non-linear effects to predict the mechanical response. To date, no universal modeling technique can precisely capture the behavior of such structures. In this work, successful representation of composite’s response was achieved by utilizing single fiber tension and compression experimental data, implemented to extend a basal-plane-realignment based non-linear carbon fiber material model. Numerical techniques were adopted to model the bending behavior of unidirectional carbon fiber composites that was recorded in a comprehensive experimental campaign. Observations show that high material non-linearity leads to a non-negligible neutral-axis shift and drastic reduction of bending modulus due to compressive softening. Tensile fiber failure is the driving mechanism in thin shells flexure allowing for elastic compressive strains of up to 3% without micro-buckling. As a result, a remarkable flexibility in thin shells is realized. With increasing thickness, the elastic flexibility is reduced as the failure-driving mode switches to compressive micro-buckling.
  • Mechanical response of highly deformable thin shell composites
    Item type: Other Conference Item
    Schlothauer, Arthur; Pappas, Georgios A.; Ermanni, Paolo (2021)
    Presentations to VIII Conference on Mechanical Response of Composites, Volume CT08 - Micro-Mechanics III
  • Resilient thin shell composites for extremely deformable structures
    Item type: Doctoral Thesis
    Schlothauer, Arthur (2021)
  • Bending failure analysis and modeling of thin fiber reinforced shells
    Item type: Journal Article
    Pappas, Georgios A.; Schlothauer, Arthur; Ermanni, Paolo (2021)
    Composites Science and Technology
    In this work, the impact of high stress gradients, found in bending of thin unidirectional fiber reinforced shells (~0.1 to 1 mm), on compressive micro-buckling failure, was analyzed. Such thin shells show increased resistance to compressive failure under high curvatures, which may even allow tensile fiber damage to drive ultimate failure for very low thickness (e.g. <0.5 mm). The main scope of this work is to analyze this increased resistance to compressive failure and propose a robust modeling scheme. The mechanical failure response was captured by a shell-buckling experimental campaign. The origins of the increased compressive failure resistance were initially attributed to the reduction of shear stresses acting on the most susceptible domain of a representative wavy fiber. This effect was effectively described by an analytically derived, stress-gradient-dependent parameter. The hypothesis for the establishment of this parameter was corroborated by a numerical micromechanical model adopting the embedded cell approach. This model also revealed important micromechanical interactions which were incorporated by simple stress and strain factors. The derived failure prediction scheme was further extended to include the non-negligible, non-linear elastic material behavior of carbon fibers by means of a numerical algorithm. The validity of the failure prediction model was demonstrated by the successful comparison with results acquired from the shell-buckling experiments on a unidirectional carbon-fiber reinforced epoxy system. To this end, the validity of the initial hypothesis of stress-gradient-dependence on compressive failure was corroborated. Major effect on the overall behavior modeling has carbon fiber's material non-linearity, as well as micromechanical interactions.
  • Effects of fiber non-linearity and matrix type on the realization of foldable structures
    Item type: Conference Paper
    Schlothauer, Arthur; Cueni, Dominik; Pappas, Georgios A.; et al. (2021)
    AIAA Scitech 2021 Forum
    High strain composite (HSC) shells made from carbon fiber (CF) reinforced polymers can enable considerable mass savings in deployable space structures. Minimizing the packaged volume while maintaining structural stiffness, is a key challenge in the design of HSC structures and requires accurate prediction of a structure’s behavior during folding. A major unknown in the design of such structures is the non-linear material behavior and its effects on the stress distribution in composite laminates. This paper addresses this challenge by experimentally quantifying and modelling non-linear material behavior in unidirectional CF-Polyether ether ketone (PEEK) composites and extending the investigations to laminate level by means of an extended laminate theory. It was found that fiber non-linearity has a positive effect on laminate's flexibility, especially in cross-ply laminates. Here, neutral axis shift delays the formation of high strains on the tensile side and can mitigate critical transverse tensile stresses in off-axis plies. The susceptibility of a lamina to transverse cracking, however, limits design choices and flexibility. This highlights the importance of a suitable matrix system for these composites, which offers sufficient transverse strength to cope with off-axis stresses. The findings are put into context of foldable structures by considering the design and manufacturing of a lenticular boom structure.
  • 3D printed mechanically representative aortic model made of gelatin fiber reinforced silicone composite
    Item type: Journal Article
    Kuthe, Sudhanshu; Schlothauer, Arthur; Bodkhe, Sampada; et al. (2022)
    Materials Letters
    Additive manufacturing (AM) is a useful technology to produce artificial aortic models for the training of transcatheter aortic valve replacement (TAVR) surgery. With AM, the models can be tailored towards the individualized aortic anatomy of patients. Most of these reported models so far are manufactured using single rubber-like materials. However, such materials do not replicate the mechanical properties of natural aortic tissue, especially the stress–strain response in higher strain (>0.1) regions. This could be problematic for surgeons training for surgeries using a model which does not exhibit properties of the real aorta. To overcome this limitation, we developed a 3D-printed, mechanically representative aortic model comprising gelatin fibers and silicone. The model is promising as a realistic analog of aortic sinus for mock TAVR surgery. Computerized tomography data was analyzed beforehand using medical imaging to identify the anatomy of a specific patient's aortic sinus and the surrounding blood vessels. A novel silicone matrix composite reinforced with gelatin fibers designed in this work was tested and compared with the stress–strain response of aortic tissue. Such a model comprising both patient-specific geometries as well as realistic material properties of aortic tissue can be helpful for the development of next-generation medical phantoms.
Publications 1 - 10 of 17