Magnetic beads play an important role in the miniaturization of clinical diagnostics systems. In lab-on-chip platforms, beads can be made to link to a target species and can then be used for the manipulation and detection of this species. Current bead actuation systems utilize complex on-chip coil systems that offer low field strengths and little versatility. We demonstrate a novel system based on an external rotating magnetic field and on-chip soft-magnetic structures to focus the field locally. These structures were designed and optimized using finite element simulations in order to create a number of local flux density maxima. These maxima, to which the magnetic beads are attracted, move over the chip surface in a continuous way together with the rotation of the external field, resulting in a mechanism similar to that of a conveyor belt. A prototype was fabricated using PDMS molding techniques mixed with iron powder for the magnetic structures. In the subsequent experiments, a quadrupole electromagnet was used to create the rotating external field. We observed that beads formed agglomerates that rolled over the chip surface, just above the magnetic structures. Field rotation frequencies between 0.1–50 Hz were tested resulting in magnetic bead speeds of over 1 mm s⁻¹ for the highest frequency. With this, we have shown that our novel concept works, combining a simple design and simple operation with a powerful and versatile method for bead actuation. This makes it a promising method for further research and utilization in lab-on-chip systems.

中文翻译：

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微流磁珠输送带

磁珠在临床诊断系统的小型化中起着重要作用。在芯片实验室平台中，可以制造珠子以链接到目标物种，然后将其用于操纵和检测该物种。当前的磁珠驱动系统利用复杂的片上线圈系统，该系统提供了低的场强和很少的通用性。我们演示了一个基于外部旋转磁场和片上软磁结构的新型系统，可以将磁场局部聚焦。使用有限元模拟对这些结构进行了设计和优化，以创建多个局部磁通密度最大值。磁珠被吸引到的这些最大值与外部磁场的旋转一起连续地在芯片表面上移动，从而产生类似于传送带的机制。使用PDMS成型技术和铁粉混合制成磁性结构的原型。在随后的实验中，使用四极电磁铁创建旋转的外部磁场。我们观察到磁珠形成的团块在芯片表面上方的磁性结构上方滚动。测试场旋转频率在0.1–50 Hz之间，导致磁珠速度超过1 mm s^-1为最高频率。以此，我们证明了我们新颖的概念是可行的，它将简单的设计和简单的操作与强大而通用的磁珠驱动方法相结合。这使其成为在芯片实验室系统中进行进一步研究和利用的有前途的方法。