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1. Clot embolization studies and computational framework for embolization in a canonical tube model

   https://doi.org/10.1038/s41598-023-41825-8  

   Tobin, Nicolas; Li, Menghan; Hiller, Gretchen; Azimi, Arash; Manning, Keefe B. (December 2023, Scientific Reports)

   Abstract Despite recent advances in the development of computational methods of modeling thrombosis, relatively little effort has been made in developing methods of modeling blood clot embolization. Such a model would provide substantially greater understanding of the mechanics of embolization, as in-vitro and in-vivo characterization of embolization is difficult. Here, a method of computationally simulating embolization is developed. Experiments are performed of blood clots formed in a polycarbonate tube, where phosphate-buffered saline is run through the tube at increasing flow rates until the clot embolizes. The experiments revealed embolization can be initiated by leading edge and trailing edge detachment or by non-uniform detachment. Stress-relaxation experiments are also performed to establish values of constitutive parameters for subsequent simulations. The embolization in the tube is reproduced in silico using a multiphase volume-of-fluid approach, where the clot is modeled as viscoelastic. By varying the constitutive parameters at the wall, embolization can be reproduced in-silico at varying flow rates, and a range of constitutive parameters fitting the experiments is reported. Here, the leading edge embolization is simulated at flow rates consistent with the experiments demonstrating excellent agreement in this specific behavior. 

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2. Mechanical properties of clot made from human and bovine whole blood differ significantly

   https://doi.org/10.1016/j.jmbbm.2024.106508  

   Sugerman, Gabriella P; Bechtel, Grace N; Malinowska, Zuzanna; Parekh, Sapun H; Rausch, Manuel K (June 2024, Journal of the Mechanical Behavior of Biomedical Materials)

   Thromboembolism – that is, clot formation and the subsequent fragmentation of clot – is a leading cause of death worldwide. Clots’ mechanical properties are critical determinants of both the embolization process and the pathophysiological consequences thereof. Thus, understanding and quantifying the mechanical properties of clots is important to our ability to treat and prevent thromboembolic disease. However, assessing these properties from in vivo clots is experimentally challenging. Therefore, we and others have turned to studying in vitro clot mimics instead. Unfortunately, there are significant discrepancies in the reported properties of these clot mimics, which have been hypothesized to arise from differences in experimental techniques and blood sources. The goal of our current work is therefore to compare the mechanical behavior of clots made from the two most common sources, human and bovine blood, using the same experimental techniques. To this end, we tested clots under pure shear with and without initial cracks, under cyclic loading, and under stress relaxation. Based on these data, we computed and compared stiffness, strength, work-to-rupture, fracture toughness, relaxation time constants, and prestrain. While clots from both sources behaved qualitatively similarly, they differed quantitatively in almost every metric. We also correlated each mechanical metric to measures of blood composition. Thereby, we traced this inter-species variability in clot mechanics back to significant differences in hematocrit, but not platelet count. Thus, our work suggests that the results of past studies that have used bovine blood to make in vitro mimics – without adjusting blood composition – should be interpreted carefully. Future studies about the mechanical properties of blood clots should focus on human blood alone. 

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3. Toward Modeling Thrombosis and Thromboembolism in Laminar and Turbulent Flow Regimes

   https://doi.org/10.1002/cnm.3638  

   Tobin, Nicolas; Manning, Keefe B. (August 2022, International Journal for Numerical Methods in Biomedical Engineering)

   Thrombosis and thromboembolism are deadly risk factors in blood-contacting biomedical devices, and in-silico models of thrombosis are attractive tools to understand the mechanics of these processes, though the simulation of thromboembolism remains underdeveloped. The purpose of this study is to modify an existing computational thrombosis model to allow for thromboembolism and to investigate the behavior of the modified model at a range of flow rates. The new and existing models are observed to lead to similar predictions of thrombosis in a canonical backward-facing step geometry across flow rates, and neither model predicts thrombosis in a turbulent flow. Simulations are performed by increasing flow rates in the case of a clot formed at lower flow to induce embolization. While embolization is observed, most of the clot breakdown is by shear rather than by breakup and subsequent transport of clotted material, and further work is required in the formulation and validation of embolization. This model provides a framework to further investigate thromboembolization. 

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4. ThermoTape: A Temperature-Responsive Medical Adhesive Minimizing MARSI Risks with Adaptability Across Applications and Wear Durations

   https://doi.org/10.1115/1.4068595  

   Liu, Ruofan; Swanson, Shawn; Huang, Ethan; Krejsa, Michael R; MacKenzie, J Devin; Kleweno, Conor P; Taroc, Ann-Marie; Nelson, Leonard Y; Seibel, Eric J (May 2025, Journal of Medical Devices)

   Abstract Medical adhesives are vital for securing wearable sensors, wound dressings, and critical medical devices. These adhesives must balance strong adhesion with patient comfort, especially when used over extended periods. Adhesives that maintain their efficacy for more than two weeks are essential for continuous monitoring devices, as they enhance diagnostic accuracy and reduce dressing changes, minimizing patient discomfort and infection risk. However, current long-wear adhesives often use aggressive acrylics that can cause skin injuries. To overcome these limitations, we developed an advanced ThermoTape offering temperature-responsive properties with a polyurethane backing for more than 14 days of wear. A double transfer coating process fabricated PU-ThermoTape, with surface morphology characterized using Atomic Force Microscopy. Differential Scanning Calorimetry and thermography determined the optimal removal window. Peeling strength tests were conducted at room and elevated temperatures to assess performance. In vitro, PU-ThermoTape displayed an average peeling strength of 0.3 N/mm at 25 °C, decreasing by 75% when heated to 45°C, with an optimal removal window of approximately 2.5 minutes. The tape demonstrated excellent skin conformity with its polyurethane backing. In a 14-day wearability study with seven volunteers, PU-ThermoTape outperformed Tegaderm, maintaining temperature-responsiveness and allowing unrestricted daily activities throughout. PU-ThermoTape provides robust adhesion, high skin conformity, and facilitates gentle removal after brief warming, positioning it as a versatile adhesive suitable for various applications with different duration requirements. 

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5. Hemocompatibility of super-repellent surfaces: current and future

   https://doi.org/10.1039/C9MH00051H  

   Movafaghi, Sanli; Wang, Wei; Bark, David L.; Dasi, Lakshmi P.; Popat, Ketul C.; Kota, Arun K. (September 2019, Materials Horizons)

   Virtually all blood-contacting medical implants and devices initiate immunological events in the form of thrombosis and inflammation. Typically, patients receiving such implants are also given large doses of anticoagulants, which pose a high risk and a high cost to the patient. Thus, the design and development of surfaces with improved hemocompatibility and reduced dependence on anticoagulation treatments is paramount for the success of blood-contacting medical implants and devices. In the past decade, the hemocompatibility of super-repellent surfaces ( i.e. , surfaces that are extremely repellent to liquids) has been extensively investigated because such surfaces greatly reduce the blood–material contact area, which in turn reduces the area available for protein adsorption and blood cell or platelet adhesion, thereby offering the potential for improved hemocompatibility. In this review, we critically examine the progress made in characterizing the hemocompatibility of super-repellent surfaces, identify the unresolved challenges and highlight the opportunities for future research on developing medical implants and devices with super-repellent surfaces. 

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