A magnetic zigzag nanowire device was designed for single cell biosensing. Nanowires with widths of 150, 300, 500, and 800 nm were fabricated on silicon trenches by electron beam lithography, electron beam evaporation, and lift-off processes. Magnetoresistance measurements were performed before and after the attachment of a single magnetic cell to the nanowires to characterize the magnetic signal change due to the influence of the magnetic cell. Magnetoresistance responses were measured in different magnetic field directions, and the results showed that this nanowire device can be used for multi-directional detection. It was observed that the highest switching field variation occurred in a 150 nm wide nanowire when the field was perpendicular to the substrate plane. On the other hand, the highest magnetoresistance ratio variation occurred in a 800 nm wide nanowire also when the field was perpendicular to the substrate plane. Besides, the trench-structured substrate proposed in this study can fix the magnetic cell to the sensor in a fluid environment, and the stray field generated by the corners of the magnetic zigzag nanowires has the function of actively attracting the magnetic cells for detection.

We designed and fabricated a micro-scaled cell gripper based on two highly flexible magnetic zigzag structures that can be actuated by a magnetic field. Elongated single domain magnetic thin films with high magnetic shape anisotropy were deposited on the zigzag structures. By adjusting the external magnetic field we were able to control the torque applied on the magnetic films that was responsible for the actuation. We measured and discussed the displacement of the zigzag structures under different magnetic fields, and we observed a hysteresis characteristic in the actuation. Furthermore, we demonstrated the ability of gripping a single cell in water solution using the designed cell microgripper. The cell microgripper proposed in this study can provide important information for future biochip and biomedical applications.

We investigated the influence of magnetic domain walls and magnetic fields on the thermal conductivity of suspended magnetic nanowires. The thermal conductivity of the nanowires was obtained using steady-state Joule heating to measure the change in resistance caused by spontaneous heating. The results showed that the thermal conductivity coefficients of straight and wavy magnetic nanowires decreased with an increase in the magnetic domain wall number, implying that the scattering between magnons and domain walls hindered the heat transport process. In addition, we proved that the magnetic field considerably reduced the thermal conductivity of a magnetic nanowire. The influence of magnetic domain walls and magnetic fields on the thermal conductivity of polycrystalline magnetic nanowires can be attributed to the scattering of long-wavelength spin waves mediated by intergrain exchange coupling.

In this review, we introduce various magnetic biosensors that have been developed. We first explain the advantages of magnetic biosensing and their general operating principles as well as the biolabeling technique for magnetic nanoparticles. Next, we focus on magnetoresistive biosensing technologies because magnetoresistive biosensors will be an essential development direction due to the demand for miniaturization and portable lab-on-a-chip devices. The magnetoresistive effects employed in biosensing include anisotropic magnetoresistance, giant magnetoresistance and tunneling magnetoresistance. In addition to magnetoresistive sensors, the advantages and disadvantages of some nonmagnetoresistive magnetic biosensors are discussed and compared. Finally, we introduce research on integrating magnetic biosensors into the microfluidic laboratory-on-a-chip systems and comment on future development trends.

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