Department of Mechanical Engineering , Clemson University , Clemson , South Carolina 29634-0921 , United States.
MOA Key Laboratory of Agricultural Information Acquisition Technology (Beijing) , China Agricultural University , Beijing 10083 , China.
Anal Chem. 2018 Jul 17;90(14):8600-8606. doi: 10.1021/acs.analchem.8b01813. Epub 2018 Jul 2.
There has been increasing interest in the use of magnetic fluids to manipulate diamagnetic particles in microfluidic devices. Current methods for diamagnetic-particle focusing in magnetic fluids require either a pair of repulsive magnets or a diamagnetic sheath flow. We demonstrate herein a tunable, sheathless focusing of diamagnetic particles in a microchannel ferrofluid flow with a single set of overhead permanent magnets. Particles are focused into a single stream near the bottom wall of a straight rectangular microchannel, where a magnetic-field minimum is formed as a result of the magnetization of the ferrofluid. This focusing can be readily switched off and on by removing and replacing the permanent magnets. More importantly, the particle-focusing position can be tuned by shifting the magnets with respect to the microchannel. We perform a systematic experimental study of the parametric effects of the fluid-particle-channel system on diamagnetic-particle focusing in terms of a defined particle-focusing effectiveness.
人们对在微流控装置中使用磁性液体来操纵抗磁粒子越来越感兴趣。目前在磁性液体中进行抗磁粒子聚焦的方法需要一对排斥磁铁或抗磁鞘流。本文展示了一种使用单个上置永磁体在无鞘流的情况下在铁磁流体微通道流中对其进行可调谐的抗磁粒子聚焦。粒子在直矩形微通道的底部壁附近被聚焦成单一流体，这是由于铁磁流体的磁化而在磁场中形成了最小值。通过移除和更换永磁体，可以轻松地打开和关闭聚焦。更重要的是，通过相对于微通道移动磁铁，可以调节粒子聚焦的位置。我们对流体-粒子-通道系统的参数效应进行了系统的实验研究，以确定粒子聚焦的有效性。
