Queensland Micro and Nanotechnology Centre, Griffith University, Brisbane, 4111, Australia.
Lab Chip. 2015 Jul 21;15(14):2998-3005. doi: 10.1039/c5lc00427f.
We report magnetic manipulation of non-magnetic particles suspended in diluted ferrofluid. Diamagnetic particles were introduced into a circular chamber to study the extent of their deflection under the effect of a non-uniform magnetic field of a permanent magnet. Since ferrofluid is a paramagnetic medium, it also experiences a bulk magnetic force that in turn induces a secondary flow opposing the main hydrodynamic flow. Sheath flow rate, particle size, and magnetic field strength were varied to examine this complex behaviour. The combined effect of negative magnetophoresis and magnetically induced secondary flow leads to various operation regimes, which can potentially find applications in separation, trapping and mixing of diamagnetic particles such as cells in a microfluidic system.
我们报告了悬浮在稀释铁磁流体中的非磁性颗粒的磁操纵。顺磁颗粒被引入到一个圆形腔室中，以研究在永磁体不均匀磁场作用下它们的偏转程度。由于铁磁流体是顺磁介质，它也会受到体磁力的作用，这反过来又会诱导出与主要流体动力流相反的二次流。改变鞘流率、颗粒尺寸和磁场强度来研究这种复杂的行为。负磁泳和磁诱导二次流的综合作用导致了各种操作模式，这些模式可能在微流控系统中分离、捕获和混合顺磁性颗粒（如细胞）方面有应用。
