The noise is the signal: exploring physico-chemical fluctuations with multiscale experimental models

噪声是实验科学中普遍存在的一个方面，通常被认为是有害的。然而，正如翁萨格提出的著名观点，波动包含着重要的信息。微观波动和宏观输运之间的这种联系在模拟研究中得到了大量的利用，但它们与物理化学实验的相关性直到现在才出现，因为单粒子水平的数据是可用的。虽然许多重要的输运现象都适用于波动分析，但由于这些系统的短时间和长度尺度以及固有的复杂性，解释来自分子实验的数据极具挑战性。该项目旨在揭示物理化学噪声的起源，从而开发从分子数据中提取和解释微观信息所需的工具，通过探索高度控制的中尺度和纳米尺度实验模型的独特组合中的波动，这些模型可以被赶出平衡状态。我将首先考虑约束和相互作用如何改变通过微流体通道驱动的胶体颗粒电流的波动。通过对轨迹的直接观察和功率谱密度的计算来量化波动，将使我能够解决围绕“有色”噪声特征的长期问题。其次，我将使用柔性的模型聚合物来探索调节受限聚合物传输的构象波动、熵和流体动力学相互作用之间的复杂相互作用。最后，我将以这些发现为基础，研究、分析和解释与柔性DNA纳米结构传输相关的离子电流波动。我的综合结果将在基础层面上为物理化学噪声提供前所未有的见解，而开发的分析工具将促进对各种现象的研究；从通过生物膜的传输，到芯片实验室设备的流动，以及功能化纳米孔的传感。

Noise is a universal aspect of experimental science, usually considered detrimental. Yet fluctuations contain significant information, as famously proposed by Onsager. Such links between microscopic fluctuations and macroscopic transport are heavily exploited by simulation studies, but their relevance to physico-chemical experiments is only now emerging as data at the single-particle level becomes available. While many important transport phenomena are amenable to fluctuation analysis, interpreting data from molecular experiments is extremely challenging, due to the short time and length scales and inherent complexity of these systems. This project aims to uncover the origins of physico-chemical noise, and thereby develop the tools required to extract and interpret microscopic information from molecular data, by exploring fluctuations in a unique combination of highly controlled mesoscale and nanoscale experimental models that can be driven out of equilibrium. I will first consider how confinement and interactions modify fluctuations in currents of colloidal particles driven through microfluidic channels. Quantifying fluctuations via direct observation of trajectories and calculation of the power spectral density will allow me to address long-standing questions surrounding 'coloured' noise signatures. Secondly, I will use flexible, model polymers to probe the complex interplay between conformational fluctuations, entropy and hydrodynamic interactions that modulate confined polymer transport. Finally, I will build on these findings to study, analyse and interpret fluctuations in the ionic currents associated with transport through flexible DNA nanostructures. My combined results will provide unprecedented insights into physico-chemical noise at a fundamental level, while the analysis tools developed will facilitate research into diverse phenomena; from transport through biological membranes, to flow in lab-on-a-chip devices and sensing with functionalised nanopores.