基于垂直巨磁阻抗效应的磁珠检测研究

The magnetic sensors based on the giant magnetoimpedance effect can be highly sensitive to the external magnetic field, which has great potential in biosensing applications. Investigations of using the giant magnetoimpedance sensors to detect the magnetic beads can provide reference and theoretical guidance for magnetic immunoassay based on the giant magnetoimpedance effect. However, there are two major issues in the early studies of particle detections based on the giant magnetoimpedance effect: firstly, previous detections of the magnetic particles were performed based on the longitudinal giant magnetoimpedance effect，quantification of high-concentration magnetic particles can not be achieved since the longitudinal external magnetic field would cause the inhomogeneous distributions of the magnetic particles. In this project, a magnetic-sensing system based on the perpendicular giant magnetoimpedance effect will be established to quantify the high-concentration magnetic beads. Secondly, the superparamagnetic particles can influence on the giant magnetoimpedance effect, the mechanism of which is still not clear. To clarify the physical mechanism, experimental studies of the influence of the stray magnetic field produced by the magnetic beads on the magnetic domains in films and numerical simulations of the influence of the stray magnetic field on magnetic permeability in films will be carried out in this project.

基于巨磁阻抗效应的磁敏传感器对外磁场相当灵敏，因而其在生物传感领域有着巨大的应用潜力。研究巨磁阻抗传感器检测超顺磁微粒可为基于巨磁阻抗效应的磁敏免疫分析提供参考数据和理论指导。然而，在早期基于巨磁阻抗效应的磁微粒检测中存在两个问题：其一，早期研究都是利用纵向巨磁阻抗效应来检测磁微粒，由于纵向外磁场会引发磁微粒分布不均匀，从而导致无法定量检测高浓度磁微粒。针对此问题，本项目拟建立一个基于垂直巨磁阻抗效应的磁敏传感系统来实现定量检测高浓度磁珠。其二，超顺磁微粒影响巨磁阻抗效应的机理还不明晰，为此，本项目拟通过实验研究磁珠产生的杂散磁场对薄膜磁畴的影响和数值仿真杂散磁场对薄膜磁导率的影响来揭示其物理机制。

本项目研究了低场巨磁阻抗效应及其磁珠检测。研究发现对垂直外磁场下的巨磁阻抗传感器施加微小偏置电流可以显著提升其阻抗的低场灵敏度与线性度，微丝巨磁阻抗传感器的横向磁场灵敏度随交流电流幅值减小而增加。研究发现磁珠固定于微腔后置于巨磁阻抗传感器表面进行检测可实现高灵敏快速检测。研究发现在地磁场下巨磁阻抗传感器能够高灵敏检测10个磁珠。本项目构建了多层膜巨磁阻抗传感器的表面磁场分布模型，进一步提出了磁标记的单分子检测方法，研究结果为发展高灵敏的快速无损磁敏免疫分析技术奠定了坚实的研究基础。