Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, Maryland 21218, USA.
J Chem Phys. 2010 Jan 28;132(4):044707. doi: 10.1063/1.3299731.
Total internal reflection microscopy (TIRM) and video microscopy (VM) are methods for nonintrusively measuring weak colloidal interactions important to many existing and emerging applications. Existing analyses of TIRM measured single particle trajectories can be used to extract particle-surface potentials and average particle diffusion coefficients. Here we develop a Fokker-Planck (FP) formalism to simultaneously extract both particle-surface interaction potentials and position dependent diffusion coefficients. The FP analysis offers several advantages including capabilities to measure separation dependent hydrodynamic interactions and nonequilibrium states that are not possible with existing analyses. The FP analysis is implemented to analyze Brownian dynamic simulations of single particle TIRM and VM experiments in several configurations. Relative effects of spatial and temporal sampling on the correct interpretation of both conservative and dissipative forces are explored and show a broad range of applicability for accessible experimental systems. Our results demonstrate the ability to extract both static and dynamic information from microscopy measurements of isolated particles near surfaces, which provides a foundation for further investigation of particle ensembles and nonequilibrium systems.
全内反射显微镜（TIRM）和视频显微镜（VM）是用于非侵入式测量弱胶体相互作用的方法，这些相互作用对许多现有和新兴的应用都很重要。现有的 TIRM 测量单颗粒轨迹的分析可用于提取颗粒-表面势和平均颗粒扩散系数。在这里，我们开发了一种福克-普朗克（FP）形式主义来同时提取颗粒-表面相互作用势和位置相关的扩散系数。FP 分析具有几个优点，包括测量分离相关的流体动力相互作用和现有分析不可能测量的非平衡状态的能力。FP 分析被应用于分析单颗粒 TIRM 和 VM 实验的布朗动力学模拟，涉及几种配置。研究了空间和时间采样对正确解释保守力和耗散力的相对影响，并展示了可用于可访问实验系统的广泛适用性。我们的结果证明了从表面附近的单个颗粒显微镜测量中提取静态和动态信息的能力，这为进一步研究颗粒系综和非平衡系统提供了基础。
