Journal of the Mechanical Behavior of Biomedical Materials最新文献_第3页

Regional variations of mechanical responses of IVD to 7 different motions: An in vivo study combined with FEA and DFIS IVD 对 7 种不同运动的机械响应的区域性变化：结合有限元分析和 DFIS 的活体研究。

IF 3.3 2区医学 Q2 ENGINEERING, BIOMEDICAL

Journal of the Mechanical Behavior of Biomedical Materials

Pub Date : 2024-10-18 DOI: 10.1016/j.jmbbm.2024.106785

Juan Du , Haiyu Dong , Meng'en Huang , Vadim V. Silberschmidt , Lin Meng , Jun Miao

The abnormal mechanical behaviour of a lumbar intervertebral disc (IVD) is commonly recognized as a direct indicator of intervertebral disc degeneration (IDD). However, current methods cannot evaluate the patient-specific mechanical performance of an IVD in vivo during movement. This study establishes a patient-specific (PS) model that combines the kinematics parameters of the lumbar spine obtained with a dual fluoroscopic imaging system (DFIS) and a finite-element (FE) method for the first time to reveal the mechanical behaviours of IVDs in vivo under seven motions. Three healthy participants were recruited for this study. CT images were obtained to create finite-element models of L3-L5 spine segments. Meanwhile, participants were required to take specific positions including upright standing, flexion, extension, left and right lateral bending, as well as left and right axial torsion in the DFIS. The in vivo kinematic parameters, calculated by registering the CT images with images obtained with DFIS, were considered as loading conditions in FE simulations. Significant differences of von Mises stresses and principal strains were found between PS model and GN model which employing a generalized moment as loading conditions, former resulting in up to 76.74 % lower strain than the GN model. Also, considerable differences were observed for five anatomical regions of the IVD (L3-L5). Under all motions, the stress in the centre region (nucleus pulposus) was the lowest, while the stress in the posterior region was the highest in extension motion. Therefore, activities such as stretching with an extension, should be avoided by patients with a herniated disc, in which the posterior region was the herniation site. The PS model combining in vivo kinematics and FE simulations shows the potential in the design and assessment of patient-specific implants.

腰椎间盘（IVD）的异常机械性能通常被认为是椎间盘退变（IDD）的直接指标。然而，目前的方法无法评估患者特定的 IVD 在体内运动时的机械性能。本研究建立了一个患者特异性（PS）模型，该模型结合了双透视成像系统（DFIS）获得的腰椎运动学参数和有限元（FE）方法，首次揭示了体内 IVD 在七种运动下的力学行为。本研究招募了三名健康参与者。研究人员通过 CT 图像创建了 L3-L5 脊柱的有限元模型。同时，参与者需要在 DFIS 中采取特定姿势，包括直立、屈曲、伸展、左侧和右侧弯曲以及左侧和右侧轴向扭转。将 CT 图像与 DFIS 图像配准计算出的体内运动学参数作为有限元模拟的加载条件。发现 PS 模型与采用广义力矩作为加载条件的 GN 模型在 von Mises 应力和主应变方面存在显著差异，前者的应变比 GN 模型低 76.74%。此外，在 IVD 的五个解剖区域（L3-L5）也发现了相当大的差异。在所有运动中，中心区域（髓核）的应力最低，而在伸展运动中，后部区域的应力最高。因此，椎间盘突出症患者应避免进行伸展运动等活动，因为后部是椎间盘突出的部位。结合体内运动学和有限元模拟的 PS 模型显示了设计和评估患者专用植入物的潜力。

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引用次数: 0

A comprehensive systematic review of marketed bone grafts for load-bearing critical-sized bone defects 对市场上用于承重临界大小骨缺损的骨移植物进行全面系统的审查。

IF 3.3 2区医学 Q2 ENGINEERING, BIOMEDICAL

Journal of the Mechanical Behavior of Biomedical Materials

Pub Date : 2024-10-18 DOI: 10.1016/j.jmbbm.2024.106782

Davide Ninarello , Alberto Ballardini , Giacomo Morozzi , Luigi La Barbera

Treatment of critical-sized bone defects typically involves implantation of a bone graft. Various types of bone grafts are nowadays marketed, categorized by their origin as allografts, xenografts, or synthetic grafts. Despite their widespread use, a comprehensive understanding of their morphology and mechanical response remains elusive. Controlling these characteristics for promoting bone growth and ensuring mechanical resistance remains challenging, especially in load-bearing districts. This study aims to systematically review existing literature to delineate the principal morpho-mechanical characteristics of marketed bone grafts designed for load-bearing applications. Furthermore, the obtained data are organized and deeply discussed to find out the relationship between different graft characteristics. Among 196 documents identified through PRISMA guidelines, encompassing scientific papers and 510(k) documents, it was observed that a majority of marketed bone grafts exhibited porosity akin to bone (>60%) and mechanical properties resembling those of low-bone volume fraction trabecular bone. The present review underscores the dearth of information regarding the morpho-mechanical characteristics of bone grafts and the incomparability of data derived from different studies, due to the absence of suitable standards and guidelines. The need for new standards and complete and transparent morpho-mechanical characterization of marketed bone grafts is finally emphasized. Such an approach would enhance the comparability of data, aiding surgeons in selecting the optimal device to meet patient’s needs.

治疗严重骨缺损通常需要植入骨移植物。目前市场上有各种类型的骨移植物，按其来源可分为异种移植物、异种移植物或合成移植物。尽管它们被广泛使用，但对其形态和机械反应的全面了解仍是空白。控制这些特性以促进骨生长并确保机械阻力仍具有挑战性，尤其是在承重区。本研究旨在系统回顾现有文献，描述市场上为承重应用而设计的骨移植物的主要形态-机械特征。此外，还对所获得的数据进行了整理和深入讨论，以找出不同移植物特征之间的关系。在通过 PRISMA 指南（包括科学论文和 510(k) 文件）确定的 196 份文件中，我们发现大多数市场上销售的骨移植物都具有类似于骨（>60%）的孔隙率和类似于低骨体积分数骨小梁的机械性能。本综述强调，由于缺乏合适的标准和指南，有关骨移植物形态力学特性的信息十分匮乏，不同研究得出的数据也不具可比性。最后，强调有必要制定新的标准，并对市场上销售的骨移植物进行完整、透明的形态力学特征描述。这种方法将提高数据的可比性，帮助外科医生选择满足患者需求的最佳设备。

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引用次数: 0

Assessment of mechanical variables best describing bone remodelling responses based on their correlation with bone density 根据机械变量与骨密度的相关性，评估最能描述骨重塑反应的机械变量。

IF 3.3 2区医学 Q2 ENGINEERING, BIOMEDICAL

Journal of the Mechanical Behavior of Biomedical Materials

Pub Date : 2024-10-18 DOI: 10.1016/j.jmbbm.2024.106773

Javier Martínez-Reina , Joaquín Ojeda , José Luis Calvo-Gallego , Peter Pivonka , Saulo Martelli

Density distribution in bones can be estimated using bone remodelling models (BRM) and applying daily normal loads to assess the stress/strain state to which the bone is subjected. These models locally relate a certain mechanical stimulus, derived from the stress/strain state, directly to bone density or to its variation over time. The background of this idea is Frost’s Mechanostat Theory, which states that overloading states tend to increase bone density and disuse states tend to decrease it. Different variables have been proposed in the literature to measure the mechanical stimulus. Strain energy density (SED) and stresses have been commonly used as mechanical stimuli, but to date their use has not been justified with convincing arguments. In this paper we have selected several variables derived from stress and strain tensors and correlated them with the distribution of bone density in the femur of 13 elderly women to conclude which would be most appropriate for use as a mechanical stimulus in a BRM. We have performed this correlation analysis for six different activities: walking normally, fast walking, stair ascent, stair descent, rising from and sitting on a chair, and jumping in place. Musculoskeletal models were used to estimate joint reaction and muscle forces of each individual for each activity. These were applied to the corresponding finite element model of the femur to obtain stress and strain tensors at each point. The variables proposed as mechanical stimulus and derived from these tensors were correlated to the actual density obtained for each individual from CT-scans. Our results show that stress variables are the best correlated with density. In contrast, the correlations of SED are very weak, so it is not a good candidate for mechanical stimulus. Strains are also weakly correlated to density, but in this case because their distribution across the femur is rather uniform. This is in agreement with the Mechanostat Theory which states that bone reacts to load changes by changing its stiffness so to keep strains in a certain interval. Consequently, a plausible choice for a remodelling criterion could be keeping that strain uniformity.

骨骼中的密度分布可以通过骨骼重塑模型（BRM）进行估算，并应用每日正常负荷来评估骨骼所承受的应力/应变状态。这些模型将从应力/应变状态得出的某种机械刺激与骨密度或骨密度随时间的变化直接联系起来。这一想法的背景是弗罗斯特的机械静力理论，该理论指出，超负荷状态往往会增加骨密度，而废用状态往往会降低骨密度。文献中提出了不同的变量来测量机械刺激。应变能量密度（SED）和应力已被普遍用作机械刺激，但迄今为止，还没有令人信服的论据证明其合理性。在本文中，我们从应力和应变张量中选取了几个变量，并将它们与 13 名老年妇女股骨中的骨密度分布相关联，从而得出结论，哪一个变量最适合用作 BRM 中的机械刺激。我们对六种不同的活动进行了相关分析：正常行走、快速行走、上楼梯、下楼梯、从椅子上站起来和坐在椅子上以及原地跳跃。我们使用肌肉骨骼模型来估算每个人在每项活动中的关节反作用力和肌肉力量。将其应用于股骨的相应有限元模型，以获得各点的应力和应变张量。根据这些张量提出的机械刺激变量与每个人从 CT 扫描中获得的实际密度相关联。结果表明，应力变量与密度的相关性最好。相比之下，SED 的相关性很弱，因此不是机械刺激的理想候选变量。应变与密度的相关性也很弱，但这是因为应变在股骨上的分布相当均匀。这与 "机械恒定理论"（Mechanostat Theory）一致，该理论认为骨骼对负荷变化的反应是改变其硬度，从而将应变保持在一定范围内。因此，重塑标准的一个合理选择就是保持应变的一致性。

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引用次数: 0

Polymer microsphere inks for semi-solid extrusion 3D printing at ambient conditions 用于环境条件下半固态挤压 3D 打印的聚合物微球油墨

IF 3.3 2区医学 Q2 ENGINEERING, BIOMEDICAL

Journal of the Mechanical Behavior of Biomedical Materials

Pub Date : 2024-10-16 DOI: 10.1016/j.jmbbm.2024.106783

Juuso Pohjola , Mika Jokinen , Tero Soukka , Mikael Stolt

Extrusion-based 3D printing methods have great potential for manufacturing of personalized polymer-based drug-releasing systems. However, traditional melt-based extrusion techniques are often unsuitable for processing thermally labile molecules. Consequently, methods that utilize the extrusion of semi-solid inks under mild conditions are frequently employed. The rheological properties of the semi-solid inks have a substantial impact on the 3D printability, making it necessary to evaluate and tailor these properties. Here, we report a novel semi-solid extrusion 3D printing method based on utilization of a Carbopol gel matrix containing various concentrations of polymeric microspheres. We also demonstrate the use of a solvent vapor-based post-processing method for enhancing the mechanical strength of the printed objects. As our approach enables room-temperature processing of polymers typically used in the pharmaceutical industry, it may also facilitate the broader application of 3D printing and microsphere technologies in preparation of personalized medicine.

基于挤压的三维打印方法在制造个性化聚合物药物释放系统方面具有巨大潜力。然而，传统的熔融挤压技术往往不适合处理热敏性分子。因此，人们经常采用在温和条件下挤压半固态油墨的方法。半固态油墨的流变特性对三维打印性能有很大影响，因此有必要对这些特性进行评估和定制。在此，我们报告了一种新型半固态挤压三维打印方法，该方法基于含有不同浓度聚合物微球的 Carbopol 凝胶基质。我们还展示了如何使用基于溶剂蒸汽的后处理方法来增强打印物体的机械强度。由于我们的方法能够在室温下加工制药业通常使用的聚合物，因此还能促进三维打印和微球技术在制备个性化药物方面的更广泛应用。

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引用次数: 0

Mechanistic insights on stabilization and destabilization effect of ionic liquids on type I collagen fibrils 离子液体对 I 型胶原纤维的稳定和失稳效应的机理研究。

IF 3.3 2区医学 Q2 ENGINEERING, BIOMEDICAL

Journal of the Mechanical Behavior of Biomedical Materials

Pub Date : 2024-10-16 DOI: 10.1016/j.jmbbm.2024.106772

Kuntala Banerjee , Christina Mathew , Chandrasekar Inbasekar , Nishter Nishad Fathima

Tuned assembly of collagen has tremendous applications in the field of biomedical and tissue engineering owing to its targeted biological functionalities. In this study, ionic liquids choline dihydrogen citrate (CDHC) and diethyl methyl ammonium methane sulfonate (AMS) have been used to regulate the self-assembly of collagen at its physiological pH by probing the assembled systems at certain concentration ratios of ionic liquids and the systems were studied using various characterization methods. Due to interaction with collagen, choline dihydrogen citrate causes delay in the collagen fibrillisation process showing no binding interactions with collagen. In contrast, diethyl methyl ammonium methane sulfonate shows crosslinking effect on collagen fibrillisation due to the electrostatic interaction with the tetrahedral hydration shell of collagen moieties. From rheological studies it was observed that the AMS treated collagen fibril at 1:1 % (w/v) has highest linear viscoelastic range, this can bear the stress under high strain compare to native collagen fibril as well as all CDHC composites. For a sustainable biomaterial or bio-scaffold, mechanical property plays pivotal role on it and from our experimental analysis we found certain composites of ionic liquid treated collagen fibrillar assembly which may act as a sustainable biomaterial or bio-scaffold. It was also evolved that, how the structure-function relationship of ionic force modulated fibrillar assembly controlling the mechanical properties of the tuned system. This self-assembled, ionic-liquid treated collagen-fibrillar system would accelerate various force modulated fibrillar network study, for mimicking the ECM and tissue engineering application.

由于胶原蛋白具有针对性的生物功能，因此调整胶原蛋白的组装在生物医学和组织工程领域有着巨大的应用前景。本研究利用离子液体柠檬酸二氢胆碱（CDHC）和甲烷磺酸二乙基甲基铵（AMS）来调节胶原蛋白在生理 pH 值下的自组装，在离子液体达到一定浓度比时对组装系统进行探测，并使用各种表征方法对系统进行研究。由于与胶原蛋白的相互作用，柠檬酸二氢胆碱会导致胶原蛋白纤维化过程延迟，显示出与胶原蛋白没有结合相互作用。与此相反，甲基磺酸二乙基甲铵由于与胶原蛋白分子的四面体水合壳发生静电作用，对胶原蛋白的纤维化产生了交联作用。流变学研究表明，经 AMS 处理的 1:1 %（w/v）胶原纤维具有最高的线性粘弹性范围，与原生胶原纤维和所有 CDHC 复合材料相比，它可以承受高应变下的应力。对于可持续生物材料或生物支架来说，机械性能起着至关重要的作用。通过实验分析，我们发现某些经离子液体处理的胶原纤维组件复合材料可用作可持续生物材料或生物支架。我们还发现，离子力的结构-功能关系如何调节纤维组装，从而控制调谐系统的机械性能。这种经离子液体处理的自组装胶原纤维系统将加速各种力调制纤维网络的研究，以模拟 ECM 和组织工程应用。

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引用次数: 0

Design of thermally programmable 3D shape memory polymer-based devices tailored for endovascular treatment of intracranial aneurysms 为颅内动脉瘤的血管内治疗设计热可编程三维形状记忆聚合物设备。

IF 3.3 2区医学 Q2 ENGINEERING, BIOMEDICAL

Journal of the Mechanical Behavior of Biomedical Materials

Pub Date : 2024-10-16 DOI: 10.1016/j.jmbbm.2024.106784

Rakesh Das , Tanner L. Cabaniss , Sergio A. Pineda-Castillo , Bradley N. Bohnstedt , Yingtao Liu , Chung-Hao Lee

Despite recent technological advancements in endovascular embolization devices for treating intracranial aneurysms (ICAs), incomplete occlusion and aneurysm recanalization remain critical challenges. Shape memory polymer (SMP)-based devices, which can be manufactured and tailored to patient-specific aneurysm geometries, possess the potential to overcome the suboptimal treatment outcome of the gold standard: endovascular coiling. In this work, we propose a highly porous patient-specific SMP embolic device fabricated via 3D printing to optimize aneurysm occlusion, and thus, improve the long-term efficacy of endovascular treatment. To facilitate device deployment at the aneurysm via Joule-heating, we introduce a stable, homogeneous coating of poly-pyrrole (PPy) to enhance the electrical conductivity in the SMP material. Using an in-house pulse width modulation circuit, we induced Joule-heating and characterized the shape recovery of the PPy-coated SMP embolic devices. We found that the employed PPy coating enables enhanced electrical and thermal conductivity while only slightly altering the glass transition temperature of the SMP material. Additionally, from a series of parametric studies, we identified the combination of catalyst concentration and pyrrole polymerization time that yielded the shape recovery properties ideal for ICA endovascular therapy. Collectively, these findings highlight a promising material coating for a future coil-free, personalized shape memory polymer (SMP) embolic device, designed to achieve long-lasting, complete occlusion of aneurysms.

尽管最近用于治疗颅内动脉瘤（ICA）的血管内栓塞装置取得了技术进步，但不完全闭塞和动脉瘤再通畅仍然是严峻的挑战。基于形状记忆聚合物（SMP）的装置可根据患者特定的动脉瘤几何形状进行制造和定制，具有克服金标准（血管内旋切）治疗效果不理想的潜力。在这项工作中，我们提出了一种通过三维打印技术制造的高多孔性患者特异性 SMP 栓塞装置，以优化动脉瘤闭塞，从而提高血管内治疗的长期疗效。为了便于通过焦耳热在动脉瘤处部署装置，我们引入了一层稳定、均匀的聚吡咯（PPy）涂层，以增强 SMP 材料的导电性。我们使用自制的脉宽调制电路诱导焦耳加热，并对涂有聚吡咯涂层的 SMP 栓塞装置的形状恢复进行了表征。我们发现，所采用的 PPy 涂层可增强导电性和导热性，而对 SMP 材料的玻璃化转变温度仅有轻微改变。此外，通过一系列参数研究，我们确定了催化剂浓度和吡咯聚合时间的组合，从而获得了理想的形状恢复特性，适用于 ICA 血管内治疗。总之，这些研究结果凸显了未来无线圈、个性化形状记忆聚合物（SMP）栓塞装置的材料涂层前景广阔，可实现动脉瘤的持久、完全闭塞。

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引用次数: 0

Microarchitectural properties of compacted cancellous bone allografts: A morphology micro-computed tomography analysis 压实松质骨异体移植物的微结构特性：形态学微型计算机断层扫描分析。

IF 3.3 2区医学 Q2 ENGINEERING, BIOMEDICAL

Journal of the Mechanical Behavior of Biomedical Materials

Pub Date : 2024-10-15 DOI: 10.1016/j.jmbbm.2024.106781

D. Putzer , J. Pallua , G. Degenhardt , D. Dammerer , M. Nogler , R. Arora

Massive bone loss poses a significant challenge in defect reconstruction. The use of compacted allografts is a valuable technique to reconstruct bone stock. This study aimed to assess the impact of compression on the microstructure of native cancellous bone chips with a micro-CT analysis.

Bone samples were harvested from 15 femoral heads donated by patients who underwent total hip arthroplasty. Bone chips were prepared using a bone mill. All samples with the same weight were compressed by 25% and 50% of their original volume and subsequently scanned with a micro-CT scanner to determine the microarchitectural morphology of the bone chips. Uniaxial compression test was carried out before and after a standardized compaction procedure.

Comparing the samples without compaction to 50%, the number of trabeculae doubled, the volume ratio doubled, and the trabeculae spacing was reduced, showing voids of 800 μm on average. The number of interlocking possibilities tripled, while no differences were seen in the trabeculae morphology. Uniaxial compression test showed a yield limit after compaction of 0.125 MPa.

Interlocking might occur three times more with a denser material than in a non-compacted sample. The increase in density comparable to manual intraoperative compaction did not lead to significant fragmentation of the allograft material. The assessed microarchitecture should, therefore, reassemble the intraoperative situation during a manual bone impaction procedure.

大量骨质流失给缺损重建带来了巨大挑战。使用压缩同种异体骨是重建骨量的一项重要技术。本研究旨在通过显微 CT 分析评估压缩对原生松质骨片微观结构的影响。骨样本取自接受全髋关节置换术的患者捐赠的 15 个股骨头。使用骨研磨机制备骨片。将重量相同的所有样本分别压缩其原始体积的 25% 和 50%，然后用显微 CT 扫描仪进行扫描，以确定骨片的微观结构形态。在标准化压实程序前后进行了单轴压缩测试。与未压实至 50%的样品相比，骨小梁数量增加了一倍，体积比增加了一倍，骨小梁间距减小，平均空隙为 800 μm。交错可能性的数量增加了两倍，而小梁的形态却没有变化。单轴压缩试验显示，压实后的屈服极限为 0.125 兆帕。与未经压实的样品相比，密度更大的材料发生交错的可能性要高出三倍。与术中人工压实相当的密度增加并不会导致同种异体移植材料明显破碎。因此，所评估的微观结构应能重现人工骨压实过程中的术中情况。

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引用次数: 0

Improved stomatognathic model for highly realistic finite element analysis of temporomandibular joint biomechanics 用于颞下颌关节生物力学高逼真度有限元分析的改进型口颌模型。

IF 3.3 2区医学 Q2 ENGINEERING, BIOMEDICAL

Journal of the Mechanical Behavior of Biomedical Materials

Pub Date : 2024-10-15 DOI: 10.1016/j.jmbbm.2024.106780

Yunfan Zhu , Jinyi Zhu , Deqiang Yin , Yang Liu

Background

Mechanical response analysis of the temporomandibular joint (TMJ) is crucial for understanding the occurrence and development of diseases. However, the realistic modeling of the TMJ remains challenging because of its complex composition and multivariate associations.

Objective

This study aims to develop a highly realistic stomatognathic model that accurately represents the geometric accuracy, structural integrity, and material properties. And further optimizes the interference and establishes the application range of the simplifications and the assumptions.

Methods

Geometric reconstruction of the bone was based on high-resolution image data, with the accuracy of the occlusal surface ensured by plaster cast model registration. Soft tissues such as cartilage, the disc, the periodontal ligament (PDL), and disc attachments often need to be approximated or assumed. Therefore, the finite element methods (FEM) was used to optimize these assumptions, including 1) the biomechanical effects of the thickness and modulus of the PDL, 2) the approximation of the geometry and material behavior of the disc, and 3) the simplification of the loading and boundary conditions.

Results

1) The deformation of the PDL causes tooth movement, which spreads to the distal condyle and further effects the TMJ load situation, 2) Disc reconstructed by MRI and hyperelastic material behavior are necessary for accurate TMJ loading analyses, 3) The loss of relative sliding movement between teeth interferes with realistic TMJ loading.

Conclusion

The improved stomatognathic model delivers highly realistic and validated simulation, offering theoretical guidance for virtual treatments and TMJ multivariate overload studies.

背景：颞下颌关节（TMJ）的机械响应分析对于了解疾病的发生和发展至关重要。然而，由于颞下颌关节的复杂构成和多变量关联，颞下颌关节的逼真建模仍具有挑战性：本研究旨在开发一个高度逼真的口颌模型，该模型能准确地表现颞下颌关节的几何精度、结构完整性和材料特性。并进一步优化干扰，确定简化和假设的应用范围：方法：骨骼的几何重建基于高分辨率的图像数据，咬合面的精确度通过石膏模型登记来保证。软组织，如软骨、椎间盘、牙周韧带（PDL）和椎间盘附件通常需要近似或假设。因此，我们使用有限元方法（FEM）来优化这些假设，包括：1）PDL 厚度和模量的生物力学效应；2）椎间盘几何形状和材料行为的近似；3）加载和边界条件的简化：1）PDL 的变形会导致牙齿移动，这种移动会扩散到远端髁状突，进一步影响颞下颌关节的负荷情况；2）磁共振成像重建的椎间盘和超弹性材料行为是精确颞下颌关节负荷分析的必要条件；3）牙齿之间相对滑动运动的丧失会干扰真实的颞下颌关节负荷：结论：改进后的口颌模型提供了高度逼真和经过验证的模拟，为虚拟治疗和颞下颌关节多元过载研究提供了理论指导。

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引用次数: 0

Experimental & numerical investigations of ultra-high-speed dynamics of optically induced droplet cavitation in soft materials 软材料中光学诱导液滴空化的超高速动力学实验与数值研究。

IF 3.3 2区医学 Q2 ENGINEERING, BIOMEDICAL

Journal of the Mechanical Behavior of Biomedical Materials

Pub Date : 2024-10-13 DOI: 10.1016/j.jmbbm.2024.106776

Bachir A. Abeid , Mario L. Fabiilli , Mitra Aliabouzar , Jonathan B. Estrada

Perfluorocarbon (PFC) droplets represent a novel class of phase-shift contrast agent with promise in applications in biomedical and bioengineering fields. PFC droplets undergo a fast liquid-gas transition upon exposure to acoustic or optical triggering, offering a potential adaptable and versatile tool as contrast agent in diagnostic imaging and localized drug delivery vehicles in therapeutics systems. In this paper, we utilize advanced imaging techniques to investigate ultra-high-speed inertial dynamics and rectified quasi-static (low-speed) diffusion evolution of optically induced PFC droplet vaporization within three different hydrogels, each of different concentrations, examining effects such as droplet size and PFC core on bubble dynamics and material viscoelastic properties. Gelatin hydrogels reveal concentration-dependent impacts on bubble expansion and material elasticity. Embedding PFC droplets in gelatin increases internal pressure, resulting in higher equilibrium radius and continuous bubble growth during quasi-static evolution. Similar trends are observed in fibrin and polyacrylamide matrices, with differences in bubble behavior attributed to matrix properties and droplet presence. Interestingly, droplet size exhibits minimal impact on bubble expansion during inertial dynamics but influences quasi-static evolution, with larger droplets leading to continuous growth beyond 60 s. Furthermore, the core composition of PFC droplets significantly affects bubble behavior, with higher boiling point droplets exhibiting higher maximum expansion and faster quasi-static dissolution rates. Overall, the study sheds light on the intricate interplay between droplet characteristics, matrix properties, and multi-timescale bubble dynamics, offering valuable insights into their behavior within biomimetic hydrogels.

全氟化碳（PFC）液滴是一类新型相移造影剂，有望应用于生物医学和生物工程领域。全氟化碳液滴在受到声学或光学触发时会发生快速的液-气转换，为诊断成像中的造影剂和治疗系统中的局部给药载体提供了一种潜在的适应性强、用途广泛的工具。在本文中，我们利用先进的成像技术研究了三种不同浓度的水凝胶中光学诱导 PFC 液滴汽化的超高速惯性动力学和整流准静态（低速）扩散演化，考察了液滴大小和 PFC 核心对气泡动力学和材料粘弹性能的影响。明胶水凝胶显示了浓度对气泡膨胀和材料弹性的影响。在明胶中嵌入 PFC 液滴会增加内部压力，导致更高的平衡半径，并在准静态演化过程中使气泡持续增长。在纤维蛋白和聚丙烯酰胺基质中也观察到类似的趋势，气泡行为的差异归因于基质特性和液滴的存在。有趣的是，液滴大小在惯性动力学过程中对气泡膨胀的影响极小，但对准静态演变的影响却很大，较大的液滴会导致气泡在 60 秒后持续增长。此外，PFC 液滴的核心成分也会对气泡行为产生重大影响，沸点较高的液滴会表现出更高的最大膨胀率和更快的准静态溶解速率。总之，这项研究揭示了液滴特性、基质特性和多时标气泡动力学之间错综复杂的相互作用，为了解它们在仿生物水凝胶中的行为提供了宝贵的见解。

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引用次数: 0

Temporal evolution of mechanical properties in PDMS: A comparative study of elastic modulus and relaxation time for storage in air and aqueous environment PDMS 机械特性的时间演变：空气和水环境中储存的弹性模量和弛豫时间比较研究

IF 3.3 2区医学 Q2 ENGINEERING, BIOMEDICAL

Journal of the Mechanical Behavior of Biomedical Materials

Pub Date : 2024-10-12 DOI: 10.1016/j.jmbbm.2024.106779

Yuanmin Zhang, Casey Adam, Henrik Rehnstrom, Sonia Contera

Polydimethylsiloxane (PDMS) is a soft, biocompatible polymer extensively employed in biomedical research, notable for its tunable mechanical properties achieved through cross-linking. While many studies have assessed the mechanical properties of PDMS utilizing macroscopic and microscopic methods, these analyses are often limited to freshly prepared samples. However, the mechanical properties of PDMS can be expected to change during prolonged exposure to water or air, such as interface polymer chain loosening or surface hardening, which are critical considerations in applications like cell culture platforms or microfluidic devices. This paper presents a comprehensive 10-day investigation of the evolution of PDMS surface mechanical properties through AFM-based nano-indentation. We focused on the most commonly utilized crosslinker-to-base ratios of PDMS, 1:10 (r10) and 1:20 (r20), under conditions of air and deionized water storage. For r10 samples, a hardening process was detected, peaking at 2.12 ± 0.35 MPa within five days for those stored in air and 1.71 ± 0.16 MPa by the third day for those immersed in water. During indentation, the samples displayed multiple contact points, suggesting the formation of distinct regions with varying mechanical properties. In contrast, r20 samples exhibited better stability, with an observed elastic modulus averaging 0.62 ± 0.06 MPa for air-stored and 0.74 ± 0.06 MPa for water-stored samples. Relaxation experiments, interpreted via the General Maxwell Model featuring two distinct component responses, a relatively consistent fast response τ₁ (on the order of 10⁻¹ s), and a more variable, slower response τ₂ (on the order of 10 s), throughout the study period. The identification of two distinct relaxation times suggests the involvement of two disparate material property regimes in the relaxation process, implying changes in the surface material composition at the interface with air/water. These variations in mechanical properties could significantly influence the long-term functionality of PDMS in various biomedical applications.

聚二甲基硅氧烷（PDMS）是一种柔软、生物相容性好的聚合物，广泛应用于生物医学研究，其显著特点是通过交联实现可调的机械特性。虽然许多研究利用宏观和微观方法评估了 PDMS 的机械特性，但这些分析通常仅限于新鲜制备的样品。然而，PDMS 的机械性能预计会在长期暴露于水或空气中的过程中发生变化，如界面聚合物链松动或表面硬化，这些都是细胞培养平台或微流控设备等应用中需要考虑的关键因素。本文通过基于原子力显微镜的纳米压痕技术，对 PDMS 表面机械性能的演变进行了为期 10 天的全面研究。在空气和去离子水储存条件下，我们重点研究了最常用的 PDMS 交联剂与碱的比例：1:10（r10）和 1:20（r20）。对于 r10 样品，检测到了硬化过程，在空气中储存的样品在五天内达到 2.12 ± 0.35 兆帕的峰值，而浸泡在水中的样品在第三天达到 1.71 ± 0.16 兆帕的峰值。在压痕过程中，样品显示出多个接触点，表明形成了具有不同机械性能的不同区域。相比之下，r20 样品表现出更好的稳定性，观察到的弹性模量平均为 0.62 ± 0.06 MPa（空气储存）和 0.74 ± 0.06 MPa（水储存）。松弛实验通过一般麦克斯韦模型进行解释，在整个研究期间有两种不同的成分反应，一种是相对一致的快速反应τ1（10-1 秒数量级），另一种是变化较大的慢速反应τ2（10 秒数量级）。两种截然不同的松弛时间的确定表明松弛过程涉及两种不同的材料特性状态，这意味着与空气/水交界处的表面材料成分发生了变化。这些机械性能的变化可能会极大地影响 PDMS 在各种生物医学应用中的长期功能。

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引用次数: 0