Martin James E
Sandia National Laboratories, Albuquerque, New Mexico 87185-1421, USA.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Jan;79(1 Pt 1):011503. doi: 10.1103/PhysRevE.79.011503. Epub 2009 Jan 27.
Recent experiments have shown that a type of triaxial magnetic field we call a vortex field can induce strong mixing in a magnetic particle suspension. A vortex triaxial field consists of a rotating magnetic field in a horizontal plane, with a dc field applied normal to this. The mixing torque is found to be independent of the field frequency and fluid viscosity over a broad range; scales as the square of the applied field; and is strongest for a balanced triaxial field-one in which the root-mean-square amplitudes of the three field components are equal. In this paper we show that these anomalous effects are consistent with the formation of volatile particle chains that have a precessionlike motion. Theoretical results are given for both particle chains and magnetic rods for arbitrary vortex field angles. A key conclusion is that the mixing torque is independent of particle size, making this mixing technique scale adaptive, and thus suitable for microfluidics applications.
最近的实验表明，我们称之为涡旋场的一种三轴磁场能够在磁性颗粒悬浮液中引发强烈的混合。涡旋三轴场由一个在水平面上旋转的磁场以及一个垂直于此施加的直流磁场组成。研究发现，在很宽的范围内，混合扭矩与场频率和流体粘度无关；与施加场的平方成正比；并且对于平衡三轴场（即三个场分量的均方根振幅相等的场）而言最强。在本文中，我们表明这些异常效应与具有类似进动运动的挥发性颗粒链的形成是一致的。针对任意涡旋场角度，给出了颗粒链和磁棒的理论结果。一个关键结论是，混合扭矩与颗粒大小无关，这使得这种混合技术具有尺度适应性，因此适用于微流体应用。
