Numerous situations involve the capture of particles onto a functionalized surface in a laminar flow, such as classical biomedical assays, lab on a chip devices or even biological research protocols. Being able to control this capture is thus an important issue that we address in this paper. We focus on a simple and widely used geometry, the straight microfluidic channel, in which particles undergo two weak effects: diffusion towards the functionalized surface and lift forces expelling them away from it. We show that the competition between these two weak mechanisms yields strongly different capture behavior whose occurrence depends on the value of a new lifto-diffusive dimensionless number \({\mathcal {N}}_{\text {LD}}\). We show that tuning the flow rate and the channel dimension to get proper values of this number allow to trigger, via a pure hydrodynamic effect, the capture or non-capture of particles on surfaces. For example, we show that, under certain conditions, doubling the flow rate reduces the capture rate by four orders of magnitude. Additionally, we provide the particle distribution in the liquid along the channel, resulting from this competition, for different \({\mathcal {N}}_{\text {LD}}\) values. We believe that this work opens new perspectives for analysis and biotechnology applications. More precisely, the proposed model should extend to any transverse force that can be written in the form of a potential energy.

许多情况涉及在层流中将粒子捕获到功能化表面上，例如经典生物医学分析、芯片实验室设备甚至生物研究协议。因此，能够控制这种捕获是我们在本文中解决的一个重要问题。我们专注于一种简单且广泛使用的几何形状，即直的微流体通道，其中粒子会受到两种微弱的影响：向功能化表面扩散和将它们从功能化表面排出的升力。我们表明，这两种弱机制之间的竞争会产生截然不同的捕获行为，其发生取决于新的升力扩散无量纲数\({\mathcal {N}}_{\text {LD}}\). 我们表明，调整流速和通道尺寸以获得该数字的适当值允许通过纯流体动力学效应触发表面上粒子的捕获或非捕获。例如，我们表明，在某些条件下，将流速加倍会使捕获率降低四个数量级。此外，我们提供了沿通道液体中的粒子分布，这是由于这种竞争，对于不同的\({\mathcal {N}}_{\text {LD}}\)值。我们相信这项工作为分析和生物技术应用开辟了新的视角。更准确地说，所提出的模型应该扩展到任何可以以势能形式写入的横向力。