Department of Nanomedicine and Biomedical Engineering, University of Texas Health Science Center at Houston, Houston, TX, USA.
Nanotechnology. 2009 Dec 9;20(49):495101. doi: 10.1088/0957-4484/20/49/495101. Epub 2009 Nov 11.
Non-spherical nano-/micro-particles can drift laterally (hydrodynamic margination) in a linear laminar flow under the concurrent effect of hydrodynamic and inertial forces. Such a feature can be exploited in the rational design of particle-based intravascular and pulmonary delivery systems and for designing new flow fractioning systems for high-throughput particle separation. A general approach is presented to predict the marginating behavior of non-spherical particles. The lateral drift velocity is shown to depend on the particle Stokes number St(a) and to grow with the size, density and rotational inertia of the particle. Elongated particles, in particular, low aspect ratio discoidal particles, exhibit the largest propensity to marginate in a linear laminar flow. In the blood microcirculation, at low shear rates (S<100 s(-1)), non-spherical particles oscillate around their trajectory and margination can only be achieved through the application of external force fields (gravitational, magnetic); whereas for larger S (100 s(-1)<S<10(4) s(-1)), micrometer particles can achieve drift velocities in the order of 1-10 microm s(-1). In the pulmonary circulation, hydrodynamic margination can be observed even for sub-micrometer particles. Finally, the inherent propensity of non-spherical particles to drift laterally can be effectively exploited for designing microfluidic devices, based on the flow fractioning approach, for particle separation without using external lateral force fields.
非球形纳米/微米颗粒在存在水动力和惯性力的共同作用下，可在层流线性流动中发生侧向漂移（水动力边缘移动）。这一特性可用于合理设计基于颗粒的血管内和肺内输送系统，并设计用于高通量颗粒分离的新型流分离系统。本文提出了一种预测非球形颗粒边缘移动行为的一般方法。研究表明，侧向漂移速度取决于颗粒的斯托克斯数 St(a)，并随颗粒的尺寸、密度和转动惯量的增大而增大。特别是，长形颗粒，特别是低纵横比的盘形颗粒，在层流线性流动中具有最大的边缘移动倾向。在血液微循环中，在低剪切速率（S<100 s(-1)）下，非球形颗粒围绕其轨迹振荡，只能通过施加外力场（重力、磁场）才能实现边缘移动；而对于较大的 S（100 s(-1)<S<10(4) s(-1)），微米级颗粒可达到 1-10 μm s(-1)量级的漂移速度。在肺循环中，即使对于亚微米级颗粒，也可观察到水动力边缘移动。最后，非球形颗粒的固有侧向漂移倾向可有效地用于设计微流控装置，基于流分离方法，在不使用外部侧向力场的情况下进行颗粒分离。
