Title: Flow induced intermittent transport shapes colloid filtration in complex media Show Chinese title

Title: 流致间歇性传输影响复杂介质中的胶体过滤

Abstract: The macroscopic phenomenon of filtration is the separation between suspended and liquid phases and it takes place in natural environments (e.g. groundwater, soil, hyporheic zone) and industrial systems (e.g. filtration plants, pharmaceutical industry, hospital care). Porous materials represent excellent filters since they are characterized by a large solid surface to which flowing particles can attach and be retained. Colloidal filtration by porous media is governed by a complex interplay between transport dynamics through intricate pore structures and surface-mediated retention. Yet, classical approaches fail to capture key properties (such as filter spatial heterogeneity) and experimental observations--e.g. non-exponential deposition profiles. A key limitation of such approaches lies in the assumption that particle attachment to solid surfaces occurs at a constant rate over a given length scale, neglecting the intrinsic heterogeneity of the medium, i.e. pore size variability. Here, we develop a multiscale microfluidic model system to directly observe colloidal transport and deposition over more than three orders of magnitude in length--from tens of microns to a meter--within a porous architecture with controlled heterogeneity. By tracking individual colloidal particles within the pores, we reveal intermittent dynamics along each trajectory: particles alternate between long-range "flights" through pore channels and short-range localized "dives" near grain surfaces. During the dives, attachment can occur at a constant rate, but the distributed flight sizes, during which attachment cannot occur, produce anomalous filtration. This is quantified by deposition profiles and breakthrough curves. A stochastic model based on a continuous time random walk (CTRW), constrained by experimental data, captures this behavior and links pore structure with macroscopic filtration. Show Chinese abstract

Abstract: 过滤的宏观现象是悬浮相和液相之间的分离，这种现象发生在自然环境（例如地下水、土壤、潜流带）和工业系统（例如过滤厂、制药行业、医疗护理）中。多孔材料作为优秀的过滤器，是因为它们具有大量的固体表面，流动的颗粒可以附着并被保留于此。通过多孔介质的胶体过滤受复杂的传输动力学与表面介导的保留之间相互作用的影响。然而，经典方法无法捕捉到关键属性（如过滤器的空间异质性）以及实验观察结果——例如非指数沉积剖面。此类方法的一个主要限制在于假设颗粒在固相表面上的附着以恒定速率发生在一个特定尺度上，忽略了介质的内在异质性，即孔径的变化。在这里，我们开发了一个多尺度微流控模型系统，用于直接观察在超过三个数量级长度范围内（从几十微米到一米）在具有控制异质性的多孔结构中的胶体传输和沉积。通过追踪孔隙内的单个胶体颗粒，我们揭示了每条轨迹上的间歇性动力学：颗粒在大范围“飞行”通过孔道和短距离局部“潜水”靠近颗粒表面之间交替。在潜水过程中，附着可以以恒定速率发生，但分布的飞行大小，在此期间无法发生附着，导致异常过滤。这通过沉积剖面和穿透曲线来量化。基于连续时间随机行走（CTRW）的随机模型，受限于实验数据，能够捕捉这种行为并将孔隙结构与宏观过滤联系起来。