In this paper, we report a MEMS room-temperature resettable thermomagnetic-track-guided magnetic-bead manipulation integrated with magnetoresistive sensing for bead-motion monitoring on a silicon wafer. The manipulation/monitoring approach consists of a magnetic bead, a chip (including thermomagnetic NiCu micro-disk tracks, Pt micro heating wires, and Ni magnetoresistive sensing elements, all fabricated on a silicon wafer), pulse-generation circuit, magnetoresistive measuring circuit, thermoelectric generator (TEG), and four external electromagnets. Because Curie temperature of the NiCu micro-disk tracks is in room-temperature range, when a NiCu track is cooled by TEG to lower than the room temperature, the track becomes ferromagnetic and thus is able to attract the bead. When the electromagnets are used to apply magnetic fields to move the bead, the bead motion is guided by the ferromagnetic track. Oppositely, when the heating-wire is used to heat the track higher than the room temperature, the track switches to paramagnetic-like and thus cannot attract the bead. When the magnetic field is applied to move the bead, the bead motion is not-guided by the paramagnetic-like track. By using these approaches, we successfully demonstrated guiding the bead moving around a track and across different tracks. By using magnetoresistive sensing, location of the bead is obtained and consequently monitoring of the bead-motion is achieved. The most important feature is that our approach can easily reset any track anytime during the bead-manipulation in room-temperature range, when comparing to conventional resetting approach which is complicated and requires to several hundred °C. In addition, our approach is the first one to combine the magnetic-track guided magnetic-bead manipulation and magnetoresistive-sensing-element based magnetic-bead motion monitoring on a silicon chip (toward a fully on-chip actuating/sensing MEMS system for magnetic bead manipulation). The results are important and alternative solutions for magnetic-track-guided magnetic bead manipulation for biomedical MEMS.

在本文中，我们报告了一种 MEMS 室温可复位热磁轨道引导磁珠操作，该磁珠操作与磁阻传感集成，用于硅晶片上的磁珠运动监测。操纵/监测方法由磁珠、芯片（包括热磁镍铜微盘轨道、铂微加热丝和镍磁阻传感元件，均制作在硅片上）、脉冲发生电路、磁阻测量电路、热电发电机 (TEG) 和四个外部电磁铁。由于NiCu微盘磁道的居里温度在室温范围内，当NiCu磁道被TEG冷却到低于室温时，磁道变成铁磁性，从而能够吸引磁珠。当使用电磁铁施加磁场来移动珠子时，磁珠运动由铁磁轨道引导。相反，当使用加热丝将轨道加热到高于室温时，轨道会变成顺磁状，因此无法吸引珠子。当施加磁场以移动珠子时，珠子的运动不受类顺磁轨道的引导。通过使用这些方法，我们成功地演示了引导珠子在轨道上和不同轨道上移动。通过使用磁阻传感，可以获得珠子的位置，从而实现对珠子运动的监测。最重要的特点是，与复杂且需要数百°C的传统重置方法相比，我们的方法可以在室温范围内的珠子操作过程中随时轻松重置任何轨迹。此外，我们的方法是第一个在硅芯片上结合磁道引导磁珠操纵和基于磁阻传感元件的磁珠运动监测的方法（朝着用于磁珠操纵的完全片上驱动/传感 MEMS 系统） . 结果是用于生物医学 MEMS 的磁轨引导磁珠操作的重要和替代解决方案。