Determination of the Key Parameters Causing Unexplained Dynamic Phenomena in High-Speed Atomic Force Microscopy

能够在极小的长度尺度上准确、快速地测量材料的物理性能是推进科学研究和技术进步的关键。 原子力显微镜，其中微米尺寸的悬臂梁用于物理探测感兴趣的材料，是在十亿分之一米的量级上对材料性质进行定量测量的主要工具之一。 然而，当在高扫描速度下进行原子力显微镜测量时，会出现无法解释的现象。 这些无法解释的现象阻碍了精确的科学测量。 目前缺乏实验数据来正确描述和模拟这些无法解释的现象。 将进行一组设计良好的实验和数值模拟，以测试与这些扫描速度现象相关的可疑变量。这项工作将实现高度定量和快速的测量，例如暴露于各种刺激或实时发生的纳米级腐蚀过程的病毒的机械性能的实时演变，并将允许在医学，生物学和材料工程等领域进行新的尖端研究，从而有利于美国经济和科学的进步。 此外，该项目的教育计划将开发一个动手，互动和便携式学习平台，将暴露K-12，本科生和研究生的原子力显微镜和其操作中使用的科学原理。 该教育计划将在科学、技术、工程和数学领域产生进一步的兴趣和保留。该项目的目标是确定导致接触模式高速原子力显微镜中观察到的扫描速度相关现象的关键参数，并开发预测这种行为的数学模型。该项目的目标将通过追求以下具体任务来实现：1）通过一系列实验系统地确定导致扫描速度现象的主要变量，这些实验控制了现象的可疑来源，如相对湿度，扫描速度，扫描角度，样品成分，流体环境和AFM针尖半径。 输出数据还将用于确定用于表征扫描速度相关现象的预测模型的函数形式。 2)进行计算流体-结构相互作用模拟，以研究扫描速度对作用在大块微悬臂上的流体动力的影响。 在高速原子力显微镜域中使用的大扫描速度将影响作用在微悬臂上的流体动力，到目前为止，该流体动力是在假设周围流体是静止的情况下计算的。 这些流体-结构相互作用模拟将用于确定数学模型，以预测由于流体速度效应而对悬臂系统产生的流体动力。这项研究将允许精确的接触模式高速原子力显微镜测量，超越地形成像，在广泛的扫描速度范围内。该奖项反映了NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

The ability to accurately and rapidly measure the physical properties of materials at extremely small length scales is key to advancing scientific research and technological progress. The atomic force microscope, in which a micrometer sized cantilevered beam is used to physically probe a material of interest, is one of the primary tools for making quantitative measurements of material properties at scales on the order of one billionth of a meter. However, when conducting atomic force microscope measurements at high scanning speeds, unexplained phenomena present themselves. These unexplained phenomena impede accurate scientific measurement. There is currently a lack of experimental data to properly characterize and model these unexplained phenomena. A set of well-designed experiments and numerical simulations that test the suspected variables related to these scanning speed phenomena will be conducted. Highly quantitative and rapid measurements, such as the real-time evolution of the mechanical properties of viruses exposed to various stimuli or nano-scale corrosion processes occurring in real-time, will be enabled by this work and will allow new and cutting-edge research in areas such as medicine, biology, and materials engineering, thus, benefiting the US economy and the progress of science. In addition, the project's educational plan will develop a hands-on, interactive, and portable learning platform that will expose K-12, undergraduate, and graduate students to atomic force microscopy and the scientific principles used in its operation. The educational plan will engender further interest and retention in the Science, Technology, Engineering, and Mathematics fields.The project objective is to determine the key parameters that cause observed scan velocity related phenomena in contact mode high-speed atomic force microscopy and to develop mathematical models that will predict this behavior. The project objective will be obtained by pursuing the following specific tasks: 1) Systematically determine the primary variables causing the scan velocity phenomena via a suite of experiments that control the suspected sources of the phenomena such as relative humidity, scan speed, scan angle, sample composition, fluid environment, and AFM tip radii. The output data will also be used to determine the functional form of predictive models used to characterize the scan velocity related phenomena. 2) Perform computational fluid-structure interaction simulations to investigate the effect of scan velocity on the hydrodynamic forces acting on the bulk microcantilever. The large scan velocities used in high-speed atomic force microscopy domains will affect the hydrodynamic forces acting on the microcantilever, which to date, are calculated under the assumption that the surrounding fluid is quiescent. These fluid-structure interaction simulations will be used to determine a mathematical model to predict the hydrodynamic forces on the cantilever system due to fluid velocity effects. This research will allow for accurate contact mode high-speed atomic force microscopy measurements that extend beyond topographical imaging, across a wide range of scan velocities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.