Department of Physics and Materials Engineering, Faculty of Technology, Tomas Bata University, Nad Stráněmi 4511, 760 05 Zlín, Czech Republic.
Anal Bioanal Chem. 2011 Feb;399(4):1481-91. doi: 10.1007/s00216-010-4163-0. Epub 2010 Sep 12.
The behavior of microparticles exposed to gravitational and lift forces and to the velocity gradient in flow velocity profile formed in microfluidic conduits is studied from the viewpoint of the transient period (the relaxation) between the moment at which a particle starts to be transported by the hydrodynamic flow and the time at which it reaches an equilibrium position, characterized by a balance of all active forces. The theoretical model allowing the calculation of the relaxation time is proposed. The numerical calculus based on the proposed model is compared with the experimental data obtained under different experimental conditions, namely, for different lengths of microfluidic channels, different average linear velocities of the carrier liquid, and different sizes and densities of the particles used in the study. The results are important for the optimization of microfluidic separation units such as microthermal field-flow fractionation channels in which the separation or manipulation of the microparticles of various origin, synthetic, natural, biological, etc., is performed under similar experimental conditions but by applying an additional thermodynamic force.
从微流道中流动速度剖面形成时的重力、升力和速度梯度对微粒子作用的瞬变期（弛豫）的角度，研究了微粒子的行为，即从微粒子开始被流体动力输送的时刻到它到达以所有作用力平衡为特征的平衡位置的时间。提出了允许计算弛豫时间的理论模型。基于所提出模型的数值计算与在不同实验条件下获得的实验数据进行了比较，即对于不同长度的微流道、不同的载液平均线性速度以及在研究中使用的不同大小和密度的粒子。这些结果对于微流分离单元的优化很重要，例如微热场流分离通道，其中在类似的实验条件下对各种来源的微粒子（合成的、天然的、生物的等）进行分离或操作，但施加了附加的热力学力。
