Collaborative Research: RUI: Non-equilibrium fluctuations and diffusion in 2D fluids

合作研究：RUI：二维流体中的非平衡波动和扩散

• 批准号: 2104573
• 负责人: Jonathan Fernsler
• 金额: $ 33.43万
• 依托单位: California Polytechnic State University Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-06-01 至 2025-05-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2104573&HistoricalAwards=false
• 关键词: Collaborative; Research; RUI; Non; equilibrium

Non-technical AbstractDiffusion, one of the most common transport processes, is ubiquitous in biological systems and is often modeled as mixing of particles of different species due to the random motion of these particles at molecular length scales. However, diffusion in liquids has been found to couple with the flow of the fluid itself. This can lead to random concentration fluctuations that were recently found to exist at the molecular length scale and up to orders of magnitude larger. While these fluctuations have been measured for three-dimensional (3D) fluids, in the constrained dimensions of a two-dimensional (2D) fluid like a bio-membrane, they may be much larger still. Using ultra-thin freely-suspended liquid crystal films and molecular monolayers deposited on the surface of water, the research team aims to quantify these fluctuations within 2D fluids during diffusion and explore their effects on molecular transport. At the same time, the theory group is developing a mathematical model for these fluctuations and running computer simulations that can mimic experiments. This work contributes to an improved understanding of colossal fluctuations during diffusion and informs their importance in bio-membranes. The collaboration with the Soft Materials Research Center at the University of Colorado Boulder provides additional opportunities for the team of undergraduate research students to work at the frontiers of materials science and launch their post graduate careers.Technical Abstract:Diffusion of particles in bio-membranes plays an essential role in biochemical processes in living organisms. The concept of diffusion has recently received renewed attention with the discovery of giant concentration fluctuations (of spatial extent approaching 10,000 times molecular length scales) that develop during diffusive mixing of three-dimensional (3D) fluids in the presence of a concentration gradient. The concentration fluctuations are expected to be even larger in two-dimensional (2D) fluids due to the larger spatial extent of hydrodynamic interactions between diffusing particles. Bio-membranes can be modeled as quasi-2D fluids, having a combination of 2D and 3D hydrodynamic features due to the presence of a bulk fluid embedding the membrane. This project studies experimentally and theoretically the spatial and temporal extent of out-of-equilibrium concentration fluctuations, the crossover from 2D to 3D behavior, and the effects of fluctuations on the aggregation rate of diffusing particles in freely suspended smectic films, a model quasi-2D fluid. The research team is using Fluorescence Recovery After Photobleaching (FRAP) of dye dissolved in the film, and a miscibility phase transition in films of a binary liquid crystal mixture as well as in a dye-doped lipid Langmuir monolayer, to measure the concentration correlation function through the crossover from 2D to 3D behavior. The theory component of the project involves performing analytic calculations and running computer simulations, based on the immersed boundary method and stochastic hydrodynamics and using initial concentration distributions characteristic of the experiments, in order to generate a comparison to the observed concentration correlation functions. The education component of the project integrates training for undergraduate students, with a particular focus on recruiting under-represented groups, to help students in future positions at industrial and academic institutions.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.

非技术性的AbstractDiffusion，最常见的传输过程之一，在生物系统中是普遍存在的，并且由于这些粒子在分子长度尺度上的随机运动，通常被建模为不同种类的粒子的混合。然而，已经发现液体中的扩散与流体本身的流动耦合。这可能导致最近发现存在于分子长度尺度和更大数量级的随机浓度波动。虽然已经针对三维（3D）流体测量了这些波动，但是在二维（2D）流体（如生物膜）的受限尺寸中，它们可能还要大得多。利用超薄自由悬浮液晶膜和沉积在水表面的分子单层，研究小组的目标是量化扩散过程中二维流体中的这些波动，并探索它们对分子传输的影响。与此同时，理论小组正在为这些波动开发一个数学模型，并运行可以模拟实验的计算机模拟。这项工作有助于更好地了解扩散过程中的巨大波动，并告知其在生物膜中的重要性。与科罗拉多大学博尔德分校软材料研究中心的合作为本科研究生团队提供了更多的机会，使他们能够在材料科学的前沿工作，并开始他们的研究生职业生涯。技术摘要：生物膜中颗粒的扩散在生物体的生化过程中起着至关重要的作用。随着在浓度梯度存在下三维（3D）流体的扩散混合期间发展的巨大浓度波动（空间范围接近10，000倍分子长度尺度）的发现，扩散的概念最近重新受到关注。由于扩散颗粒之间的流体动力学相互作用的空间范围更大，预计在二维（2D）流体中的浓度波动甚至更大。生物膜可以被建模为准2D流体，由于包埋膜的本体流体的存在而具有2D和3D流体动力学特征的组合。本计画从实验与理论上研究自由悬浮近晶薄膜（一种准二维流体模型）中，非平衡浓度波动的空间与时间范围、二维至三维行为的交叉，以及波动对扩散粒子聚集速率的影响。 该研究小组正在使用溶解在薄膜中的染料的光漂白后荧光恢复（FRAP），以及二元液晶混合物薄膜以及染料掺杂的脂质朗缪尔单层中的可溶解性相变，通过从2D到3D行为的交叉来测量浓度相关函数。该项目的理论部分涉及进行分析计算和运行计算机模拟，基于浸没边界法和随机流体力学，并使用实验的初始浓度分布特征，以便与观测到的浓度相关函数进行比较。该项目的教育部分整合了对本科生的培训，特别注重招募代表性不足的群体，以帮助学生在工业和学术机构的未来职位上。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响力审查标准进行评估，被认为值得支持。