Chen I-Jane, Eckstein Eugene C, Lindner Erno
Department of Biomedical Engineering, The University of Memphis, Memphis, TN 38152, USA.
Lab Chip. 2009 Jan 7;9(1):107-14. doi: 10.1039/b808660e. Epub 2008 Oct 20.
Motion in micro-channels of passive flow micro-fluidic systems can be controlled by proper design and estimated by careful modeling. We report on methods to describe the flow rate as function of time in a passive pump driven micro-fluidic system. The model considers the surface energy present in small droplets, which prompts their shrinkage and induces flow. The droplet geometries are controlled by the micro-fluidic system geometry and hydrophilicity of the droplet channel contact area so that the chord of the droplet's cross section is restrained as the fluid is pumped. The model uses interfacial thermodynamics and the Hagen-Poiseuille equation for calculating the flow rate in micro-channels. Existing analyses consider the theoretical relationships among sample volume and induced flow rate, surface energy of the drops at the entrance and exit ports, and the resistance to flow. This model provides more specific information on the influence of the experimental conditions in computations of the flow rate. The model was validated in four sets of experiments. Passive pumps with 1.8 mm diameter, hydrophobic or hydrophilic entry ports, 5.0 or 10.0 mm channel length, and 2.5 or 3.3 mm diameter reservoir ports provided initial flow rates between 85 nL s(-1) and 196 nL s(-1).
被动流动微流体系统微通道中的运动可通过适当设计来控制，并通过精细建模进行估算。我们报告了在被动泵驱动的微流体系统中描述流速随时间变化的方法。该模型考虑了小液滴中存在的表面能，这促使它们收缩并引发流动。液滴的几何形状由微流体系统的几何形状和液滴通道接触区域的亲水性控制，以便在泵送流体时限制液滴横截面的弦长。该模型使用界面热力学和哈根-泊肃叶方程来计算微通道中的流速。现有分析考虑了样品体积与诱导流速、进出口处液滴的表面能以及流动阻力之间的理论关系。该模型在流速计算中提供了关于实验条件影响的更具体信息。该模型在四组实验中得到了验证。直径为1.8毫米、具有疏水或亲水入口、通道长度为5.0或10.0毫米以及储液器端口直径为2.5或3.3毫米的被动泵提供了85纳升每秒至196纳升每秒之间的初始流速。
