Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA.
Sci Rep. 2017 Aug 31;7(1):10139. doi: 10.1038/s41598-017-10149-9.
Directed transport of biological species across the surface of a substrate is essential for realizing lab-on-chip technologies. Approaches that utilize localized magnetic fields to manipulate magnetic particles carrying biological entities are attractive owing to their sensitivity, selectivity, and minimally disruptive impact on biomaterials. Magnetic domain walls in magnetic tracks produce strong localized fields and can be used to capture, transport, and detect individual superparamagnetic microbeads. The dynamics of magnetic microbead transport by domain walls has been well studied. However, demonstration of more complex functions such as selective motion and sorting using continuously driven domain walls in contiguous magnetic tracks is lacking. Here, a junction architecture is introduced that allows for branching networks in which superparamagnetic microbeads can be routed along dynamically-selected paths by a combination of rotating in-plane field for translation, and a pulsed out-of-plane field for path selection. Moreover, experiments and modeling show that the select-field amplitude is bead-size dependent, which allows for digital sorting of multiple bead populations using automated field sequences. This work provides a simple means to implement complex routing networks and selective transport functionalities in chip-based devices using magnetic domain wall conduits.
生物物种在基底表面的定向输运对于实现片上实验室技术至关重要。利用局部磁场来操纵携带生物实体的磁性颗粒的方法因其灵敏度、选择性以及对生物材料的最小干扰性而具有吸引力。磁性轨道中的磁畴壁会产生强的局域场，可用于捕获、传输和检测单个超顺磁微珠。畴壁驱动的磁性微珠输运动力学已得到很好的研究。然而，利用连续驱动的磁畴壁在连续磁轨中实现更复杂的功能，如选择性运动和分类，尚缺乏相关研究。本文提出了一种结型结构，它允许形成分支网络，通过旋转的面内磁场实现平移，以及脉冲的面外磁场实现路径选择，从而使超顺磁微珠能够沿着动态选择的路径进行路由。此外，实验和模拟表明，选择场的幅度与微珠的大小有关，这使得使用自动化场序列对多个微珠群体进行数字分类成为可能。这项工作为使用磁畴壁导管在基于芯片的设备中实现复杂的路由网络和选择性传输功能提供了一种简单的方法。
