微胶通过狭窄毛细管的迁移
Microgel Translocation Through Narrow Capillaries
AI总结：
研究揭示了微胶在狭窄毛细管中迁移的机械和拓扑限制，通过相图分析了凝胶刚度、管径和力之间的关系，为微流体和药物递送提供了工程指导。
摘要：
软黏弹性凝胶在受限几何结构中的运输是生物医学、生物学和工业系统中关键过程的基础。在这里，我们研究了一个球形微胶通过一个直径小于其平衡凝胶尺寸的狭窄毛细管的迁移。通过结合粗粒分子动力学模拟、平均场理论和机械分析，我们发现了一个临界直径$ d_c $，在此直径以下，无论施加的压力如何，微胶都无法进入。这个几何限制源于凝胶弹性与其内部网络连通性的相互作用，通过图论模型定量捕捉。我们构建了一个参数空间中的相图，参数包括管直径$ d $、施加力$ f_g $和凝胶刚度$ Y $（杨氏模量），该相图区分了成功迁移和机械停滞的区域。在壁摩擦可忽略的情况下，凝胶的移动性与施加的力成正比；然而，在网络拓扑学设定的截止点之后，随着在狭窄处的密度增加，微胶停止迁移。我们的结果揭示了在受限空间中软凝胶运输的机械和拓扑决定因素，并为微流体、药物递送和组织级过滤中的凝胶基系统工程提供了预测指南。
英文摘要：
The transport of soft viscoelastic gels through confined geometries underlies critical processes in biomedical, biological, and industrial systems. Here, we examine the translocation of a spherical microgel through a narrow capillary whose diameter is smaller than the equilibrium gel size. Using coarse-grained molecular dynamics simulations in tandem with mean-field theory and mechanical analysis, we uncover a critical threshold diameter $d_c$ below which the microgel cannot enter, regardless of the applied pressure. This geometric limit emerges from the interplay between gel elasticity and its internal network connectivity, captured quantitatively by a graph-theoretic model. We construct a phase diagram in the parameter space of tube diameter $d$, applied force $f_g$, and gel stiffness $Y$ (Young's modulus), which delineates the regimes of successful translocation and mechanical arrest. Under negligible wall friction, gel mobility scales with the applied force; however, beyond a cutoff set by the network topology, progressive densification in the constriction stalls the microgel. Our results reveal the mechanical and topological determinants of soft-gel transport in confinement and provide predictive guidelines for engineering gel-based systems in microfluidics, drug delivery, and tissue-level filtration.
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