Molecular Dynamic Assessment of Carbon Nanotube Drag In Physiologic Conditions

生理条件下碳纳米管阻力的分子动态评估

• 批准号: 8303980
• 负责人: ADRIN GHARAKHANI
• 金额: $ 7.69万
• 依托单位: APPLIED SCIENTIFIC RESEARCH
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-07-19 至 2014-05-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8303980
• 关键词: Accounting; Address; Adoption; Aerosols; Air; Caliber; Carbon Nanotubes; Communities; Computer software; Data; Dependence; Deposition; Development; Drug Formulations; Environmental Health; Exposure to; Fiber; Future; Health; Heart; Human; Humidity; Journals; Length; Link; Liquid substance; Literature; Lung; Measurement; Measures; Mechanics; Modeling; Motion; Nanotubes; Outcome; Particulate; Physiological; Production; Property; Publications; Relative (related person); Research; Respiratory System; Respiratory tract structure; Review Literature; Risk; Series; Shapes; Solid; Toxic effect; Ultrafine; Upper respiratory tract; Water; base; density; experience; exposed human population; fibrogenesis; interest; literature survey; manufacturing process; molecular dynamics; nanomaterials; nanoscale; particle; respiratory; simulation; supercomputer; symposium; tool; ultrafine particle

DESCRIPTION (provided by applicant): The growing ubiquity of carbon nanotubes (CNTs) has raised serious concerns about the potential human health and environmental implications of ultrafine particles in general, and manufactured nanomaterials in particular. To this end, while significant research is conducted to ascertain the material toxicity of nanotubes and their potential, for example, to stimulate pulmonary fibrogenesis, aerosol dynamics simulation tools can serve as a valuable complementary asset to investigate the link between the respiratory flow, the ensuing dynamics of nanotubes in the respiratory tracts, and the eventual deposition of CNTs on the respiratory system walls. A typical outcome of such an analysis would be an estimate of how deep, and at what concentration levels and distributions, CNTs of various sizes and types would penetrate in the respiratory tract under physiologic flow conditions. At the heart of a successful nanotube dynamics simulation lies the availability of accurate models for forces experienced by the nanotube. The dominant forces in the nanometer scale are drag and Brownian motion, where the former is the focus of this proposal. An order of magnitude analysis of the length scales reveals that, depending on the size and orientation of the CNT with respect to the freestream, there may be two flow regimes of relevance to CNT drag - free-molecule and transition. Yet, a review of the literature reveals an absence of drag formulae for nanotubes in these flow regimes. To address this critical and unmet CNT dynamics modeling need, the Specific Aim proposed for this project is to perform a series of Molecular Dynamics simulations of air flow over CNTs under physiologically realistic conditions, and to obtain the drag on the CNT as a function of the relative humidity of the respiratory tract; the flow rate; the inclination angle of the CNT with respect to the streamwise direction; as well as the CNT diameter, chirality, aspect ratio, and end effects. The simulation data will be analyzed and reduced into a drag coefficient function. The results will be presented at an aerosol-related conference and subsequently submitted to (aerosol) journals for publication so as to make the drag coefficient function available to the wider scientific community; thereby, enabling future aerosol dynamics simulations of CNT flow in dry or moist air. PUBLIC HEALTH RELEVANCE: The ability to accurately predict the transport and deposition details of carbon nanotubes in the human respiratory tract can be of significant benefit to making successful toxicologic impact assessments, establishing appropriate environmental standards, and determining safe exposure limits. The capability to make such predictions hinges, as a minimum, on the availability of accurate drag coefficients for carbon nanotubes under physiologically correct flow conditions. Yet, such drag coefficient data for nanotubes are absent in the literature. The objective of this research is to fill this critical gap, and to develp drag coefficient data using results from a series of simulations, which will be conducted during the project.

描述(申请人提供)：碳纳米管(CNT)的日益普遍引起了人们对超细颗粒，特别是人造纳米材料对人类健康和环境的潜在影响的严重关注。为此，虽然已经进行了大量研究来确定纳米管的材料毒性及其潜在的刺激肺纤维化的作用，但气溶胶动力学模拟工具可以作为宝贵的补充资产，用于研究呼吸流动、随后纳米管在呼吸道中的动态以及碳纳米管最终沉积在呼吸系统壁上之间的联系。这种分析的典型结果将是估计在生理流动条件下，不同大小和类型的碳纳米管将穿透呼吸道的深度以及浓度水平和分布。一个成功的纳米管动力学模拟的核心是对纳米管所经历的力的准确模型的可用性。纳米尺度上的主要作用力是阻力和布朗运动，其中阻力和布朗运动是本方案的重点。长度尺度的数量级分析表明，根据碳纳米管相对于自由流的大小和取向，可能存在与碳纳米管无阻力分子和转变相关的两种流型。然而，回顾文献发现，在这些流动状态下，纳米管的阻力公式是不存在的。为了解决这一关键的和未得到满足的碳纳米管动力学建模需求，本项目提出的具体目标是在生理现实条件下对碳纳米管上的空气流动进行一系列分子动力学模拟，并获得作为呼吸道相对湿度、流速和倾斜度的函数的碳纳米管上的阻力 碳纳米管相对于流向的角度；以及碳纳米管直径、手性、纵横比和末端效应。对模拟数据进行分析，并将其简化为阻力系数函数。结果将在一次与气溶胶有关的会议上公布，随后提交给(气溶胶)期刊发表，以便向更广泛的科学界提供阻力系数函数；从而使未来能够对碳纳米管在干燥或潮湿空气中的流动进行气溶胶动力学模拟。 与公众健康相关：能够准确预测碳纳米管在人体呼吸道中的运输和沉积细节，对于成功地进行毒理学影响评估、建立适当的环境标准和确定安全暴露限值具有重要意义。做出这种预测的能力至少取决于在生理上正确的流动条件下碳纳米管的准确阻力系数的可用性。然而，这种纳米管的阻力系数数据在文献中是不存在的。这项研究的目的是填补这一关键空白，并利用将在项目期间进行的一系列模拟的结果来开发阻力系数数据。