Soft, Structured Layers on the Surface of a Quartz Crystal Microbalance (QCM): A Computational Model to Predict Shifts of Frequency and Bandwidth Based on the Lattice-Boltzmann Method

石英晶体微天平 (QCM) 表面的软结构化层：基于格子-玻尔兹曼方法预测频率和带宽变化的计算模型

• 批准号: 324062370
• 负责人: Professor Dr.-Ing. Gunther Brenner
• 金额: --
• 依托单位: Institut für Physikalische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2021-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/324062370?language=en
• 关键词: Soft; Structured; Layers; Surface; Quartz

Building on a linearized variant of the Lattice Boltzmann Method (termed Frequency-Domain Lattice-Boltzmann Method), a simulation package shall be developed, which models the behavior a quartz crystal microbalance (QCM) in contact with structured samples in the liquid phase. While the method shall be applicable to samples with arbitrary shape, this work shall focus on particulate adsorbates with a thickness much below the wavelength of sound (such adsorbed globular proteins). Among the parameters to be varied is the coverage. The parameters to be predicted are the shifts of resonance frequency and resonance bandwidth on the different overtones of the resonator. Analytical models predicting these parameters exist for planar layer systems, but not for laterally heterogeneous samples. A first step shall be to quantify the contribution of the liquid mass trapped between adsorbed particles to the overall apparent mass, where the latter is calculated from the frequency shift with the (very simple) Sauerbrey equation. Particles of variable size, shape, and orientation shall be randomly deposited on the resonator surface, where the algorithm doing so shall allow for clustering. A second step shall be to study the consequences of a finite compliance of the contact between the particle and the substrate. Finite compliance is expected to increase the resonance bandwidth. This expectation shall be tested and be turned into a quantitative prediction. Strategies for inversion shall be identified: For certain configurations of practical importance, rules shall be derived, which allow to infer parameters of the sample (such as the average height of the particles, the stiffness of link, or the degree of clustering) from the experimentally determined values as a function of overtone order and coverage. Later in the project, the code shall be improved with regard to the accuracy, by which the forces at the particle surfaces are obtained. This step will be important for the study of adsorbates with sizes comparable to the wavelength of sound. For the current code, such layers pose a technical problem, which can be circumvented if the layers are acoustically thin. Adsorbed particles with a thickness of the order of the wavelength of sound often display so-called coupled resonances. Coupled resonances can be viewed as adsorption lines in shear-wave spectroscopy. There is a far-reaching analogy to vibrational spectroscopy on molecules. In particular, there is a mode-assignment problem, meaning that a coupled resonance can be caused by different modes of motion of the adsorbed object. The mode assignment problem shall be solved by the proposed work. In particular, it shall be clarified for a given experimental example, whether the coupled resonance is caused by a rocking mode, which exerting a bending stress at the link, or a slipping mode which exerts a tangential stress.

在晶格Boltzmann方法的线性变体（称为频域晶格 - 玻尔兹曼方法）的基础上，应开发一个模拟套件，该套件与液相中的结构样品接触，对行为a构图。虽然该方法应适用于具有任意形状的样品，但该工作应集中于颗粒吸附物，其厚度低于声音波长（此类吸附的球状蛋白）。覆盖范围是要多样化的参数。要预测的参数是共振频率和共振带宽在谐振器的不同层面上的变化。对于平面层系统存在预测这些参数的分析模型，但对于横向异质样品而不是。第一步是量化被吸附的颗粒之间的液体质量的贡献，即通过（非常简单）（非常简单的）sauerbrey方程来计算后者的整体质量。尺寸，形状和方向的颗粒应随机沉积在谐振器表面上，在此算法应允许聚类。第二步是研究粒子与底物之间接触的有限遵从性的后果。有限的合规性预计会增加共振带宽。该期望应进行测试，并将其变成定量预测。应确定反演的策略：对于某些实际重要性的配置，应得出规则，从实验确定的值中推断出样品的参数（例如，粒子的平均高度，链接的平均高度，链接的刚度或聚类程度），这是代表顺序和覆盖范围的函数。在项目的稍后，应根据准确性提高代码，从而获得粒子表面上的力。此步骤对于与声音波长相当的尺寸的吸附物的研究将很重要。对于当前代码，此类层构成了技术问题，如果层较薄，则可以规避。声音波长厚度的吸附颗粒通常显示出所谓的耦合共振。耦合共振可以看作是剪切波光谱中的吸附线。与分子上的振动光谱相比，有一个深远的类比。特别是，存在模式分配问题，这意味着耦合的共振可能是由吸附对象的不同运动模式引起的。模式分配问题应通过拟议的工作解决。特别是，对于给定的实验示例，应阐明耦合共振是由摇摆模式引起的，该模式在链路上发挥弯曲应力，还是施加切向应力的滑动模式。