Departamento de Electricidad y Electrónica, Universidad del País Vasco UPV/EHU, 48940 Leioa, Spain.
Basque Centre for Materials, Applications and Nanostructures, BCMaterials, 48940 Leioa, Spain.
Sensors (Basel). 2020 Mar 31;20(7):1961. doi: 10.3390/s20071961.
The performance of magneto-impedance sensors to detect the presence and concentration of magnetic nanoparticles is investigated, using finite element calculations to directly solve Maxwell's equations. In the case of superparamagnetic particles that are not sufficiently magnetized by an external field, it is assumed that the sensitivity of the magneto-impedance sensor to the presence of magnetic nanoparticles comes from the influence of their magnetic permeability on the sensor impedance, and not from the stray magnetic field that the particles produce. The results obtained not only justify this hypothesis, but also provide an explanation for the discrepancies found in the literature about the response of magneto-impedance sensors to the presence of magnetic nanoparticles, where some authors report an increasing magneto-impedance signal when the concentration of magnetic nanoparticles is increased, while others report a decreasing tendency. Additionally, it is demonstrated that sensors with lower magneto-impedance response display larger sensitivities to the presence of magnetic nanoparticles, indicating that the use of plain, nonmagnetic conductors as sensing materials can be beneficial, at least in the case of superparamagnetic particles insufficiently magnetized in an external magnetic field.
采用有限元法直接求解麦克斯韦方程组，研究了磁阻抗传感器检测磁性纳米粒子存在和浓度的性能。对于在外磁场中未充分磁化的超顺磁粒子，假设磁阻抗传感器对磁性纳米粒子存在的灵敏度来自于它们的磁导率对传感器阻抗的影响，而不是来自于粒子产生的杂散磁场。所得到的结果不仅验证了这一假设，而且还解释了文献中关于磁阻抗传感器对磁性纳米粒子存在的响应的差异，有些作者报告说随着磁性纳米粒子浓度的增加，磁阻抗信号增加，而另一些作者则报告说呈下降趋势。此外，还证明了磁阻抗响应较低的传感器对磁性纳米粒子的存在具有更高的灵敏度，这表明至少在外部磁场中未充分磁化的超顺磁粒子的情况下，使用普通的非磁性导体作为传感材料可能是有益的。
