Department of Mechanical Engineering and Materials Science, Duke University, Box 90300 Hudson Hall, Durham, NC 27708, USA.
Department of Biomedical Engineering, Duke University, Durham, North Carolina 27708, USA.
Lab Chip. 2016 Oct 18;16(21):4181-4188. doi: 10.1039/c6lc00878j.
The ability to direct and sort individual biological and non-biological particles into spatially addressable locations is fundamentally important to the emerging field of single cell biology. Towards this goal, we demonstrate a new class of magnetophoretic transistors, which can switch single magnetically labeled cells and magnetic beads between different paths in a microfluidic chamber. Compared with prior work on magnetophoretic transistors driven by a two-dimensional in-plane rotating field, the addition of a vertical magnetic field bias provides significant advantages in preventing the formation of particle clumps and in better replicating the operating principles of circuits in general. However, the three-dimensional driving field requires a complete redesign of the magnetic track geometry and switching electrodes. We have solved this problem by developing several types of transistor geometries which can switch particles between two different tracks by either presenting a local energy barrier or by repelling magnetic objects away from a given track, hereby denoted as "barrier" and "repulsion" transistors, respectively. For both types of transistors, we observe complete switching of magnetic objects with currents of ∼40 mA, which is consistent over a range of particle sizes (8-15 μm). The switching efficiency was also tested at various magnetic field strengths (50-90 Oe) and driving frequencies (0.1-0.6 Hz); however, we again found that the device performance only weakly depended on these parameters. These findings support the use of these novel transistor geometries to form circuit architectures in which cells can be placed in defined locations and retrieved on demand.
能够将单个生物和非生物颗粒定向和分类到空间可寻址的位置，这对于新兴的单细胞生物学领域至关重要。为此，我们展示了一类新型的磁控晶体管，它可以在微流控室中将单个磁性标记的细胞和磁性珠切换到不同的路径。与以前基于二维平面旋转磁场驱动的磁控晶体管相比，外加垂直磁场偏置在防止颗粒团聚和更好地复制一般电路的工作原理方面具有显著优势。然而，三维驱动场需要对磁轨几何形状和开关电极进行全面重新设计。我们通过开发几种晶体管几何形状解决了这个问题，这些晶体管几何形状可以通过提供局部能垒或排斥磁性物体远离给定轨道来将颗粒从一个轨道切换到另一个轨道，分别称为“阻挡”和“排斥”晶体管。对于这两种类型的晶体管，我们观察到电流约为 40 mA 时磁性物体的完全切换，这在一系列颗粒尺寸（8-15 μm）范围内是一致的。还在各种磁场强度（50-90 Oe）和驱动频率（0.1-0.6 Hz）下测试了开关效率；然而，我们再次发现，器件性能仅弱依赖于这些参数。这些发现支持使用这些新型晶体管几何形状形成电路架构，其中可以将细胞放置在定义的位置并按需检索。
