泰勒分散通道流中胶体的跨流线扩散泳迁移
Cross-streamline diffusiophoretic migration of colloids in Taylor-dispersed channel flows
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中文总结 AI 辅助
研究泰勒分散通道流中胶体跨流线扩散泳迁移，发现溶质残余横向梯度驱动迁移，吸引和排斥前沿分别使颗粒移向不同流线，通过模拟和实验证实相关动力学，渐近溶质场与非扩散轨迹模型可捕捉相关特征。
中文摘要 AI 辅助
在压力驱动通道流中，胶体的扩散泳输运通常在两个极限情况下进行分析：早期溶质场为全二维的情况，以及后期宏观输运情况，此时横截面均匀化仅在颗粒上留下微弱的轴向偏差。然而，对于胶体，许多实验在\(a^2/D_{\mathrm s}\ll t\ll a^2/D_{\mathrm p}\)的宽泛中间窗口内进行：溶质已进入泰勒分散状态，但颗粒在间隙中仍有效非扩散。研究表明泰勒分散溶质保留了残余横向梯度，相对于轴向梯度它由佩克莱特数增强且仅按\(t^{-1/2}\)衰减。该梯度在溶质浓度中较小，但在\(\nabla\ln c\)中足够大以驱动胶体的跨流线迁移。吸引前沿使颗粒移向更快的中心线流线，排斥前沿则相反。直接模拟和微流控实验证实了这些前沿锐化和拓宽动力学。渐近泰勒状态溶质场与非扩散轨迹模型结合，捕捉到了观察到的前沿几何形状、密度分布和去除动力学。结果表明，即使溶质浓度几乎横截面均匀，泰勒分散溶质场对颗粒仍可保持动态二维。
英文摘要
Diffusiophoretic transport of colloids in pressure-driven channel flow is commonly analysed in two limits: an early-time regime in which the solute field is fully two-dimensional, and a late-time macrotransport regime in which cross-sectional homogenization leaves only a weak axial bias on the particles. For colloids, however, many experiments operate in the broad intermediate window \(a^2/D_{\mathrm s}\ll t\ll a^2/D_{\mathrm p}\): the solute has entered the Taylor-dispersion regime, but the particles remain effectively non-diffusive across the gap. We show that the Taylor-dispersed solute retains a residual transverse gradient that is Péclet-enhanced relative to the axial gradient and decays only as \(t^{-1/2}\). This gradient is small in the solute concentration but large enough in \(\nabla\ln c\) to drive cross-streamline migration of colloids. Attractive fronts (\(c_{\mathrm f}>c_{\mathrm i}\)) move particles toward faster centreline streamlines, sharpening the leading edge and accelerating removal; repulsive fronts (\(c_{\mathrm f}<c_{\mathrm i}\)) move particles toward slower near-wall streamlines, broadening the trailing edge and delaying removal. Direct simulations and microfluidic experiments confirm these front-sharpening and front-broadening dynamics. An asymptotic Taylor-regime solute field, combined with a non-diffusive trajectory model, captures the observed front geometries, density profiles, and removal dynamics. The results show that Taylor-dispersed solute fields can remain dynamically two-dimensional for particles, even when their concentration is nearly cross-sectionally uniform.
