Flattening of Diluted Species Profile via Passive Geometry in a Microfluidic Device

In recent years, microfluidic devices have become an important tool for use in lab-on-a-chip processes, including drug screening and delivery, bio-chemical reactions, sample preparation and analysis, chemotaxis, and separations. In many such processes, a flat cross-sectional concentration profile with uniform flow velocity across the channel is desired to achieve controlled and precise solute transport. This is often accommodated by the use of electroosmotic flow, however, it is not an ideal for many applications, particularly biomicrofluidics. Meanwhile, pressure-driven systems generally exhibit a parabolic cross-sectional concentration profile through a channel. We draw inspiration from finite element fluid dynamics simulations to design and fabricate a practical solution to achieving a flat solute concentration profile in a two-dimensional (2D) microfluidic channel. The channel possesses geometric features to passively flatten the solute profile before entering the defined region of interest in the microfluidic channel. An obviously flat solute profile across the channel is demonstrated in both simulation and experiment. This technology readily lends itself to many microfluidic applications which require controlled solute transport in pressure driven systems.

近年来，微流控装置已成为芯片实验室流程中的一种重要工具，这些流程包括药物筛选与递送、生化反应、样品制备与分析、趋化性以及分离等。在许多此类流程中，为了实现对溶质传输的控制和精确性，需要在通道内具有均匀流速的平坦横截面浓度分布。这通常通过使用电渗流来实现，然而，对于许多应用（尤其是生物微流控领域）来说，它并非理想选择。同时，压力驱动系统通常在通道中呈现抛物线形的横截面浓度分布。我们从有限元流体动力学模拟中获得灵感，设计并制造了一种实用的解决方案，以在二维微流控通道中实现平坦的溶质浓度分布。该通道具有几何特征，可在溶质进入微流控通道中定义的感兴趣区域之前使其浓度分布被动地变平坦。在模拟和实验中都展示了通道内明显平坦的溶质浓度分布。这项技术很容易应用于许多在压力驱动系统中需要控制溶质传输的微流控应用。