Abstract
Thin-film magneto-impedance (MI) biosensors have attracted significant attention due to their high sensitivity and easy miniaturization. However, further improvement is required to detect weak biomagnetic signals. Here, we report a meander thin-film biosensor preparation to investigate the fabrication parameters influencing the MI effect. Specifically, we hypothesized that an optimal film thickness and sensing area size ratio could be achieved to obtain a maximum MI ratio. A meander multilayer MI biosensor based on a NiFe/Cu/NiFe thin-film was designed and fabricated into 3-, 6-, and 9-turn models with film thicknesses of 3 µm and 6 µm. The 9-turn biosensor resembled the largest sensing area, while the 3- and 6-turn biosensors were designed with identical sensing areas. The results indicated that the NiFe film thickness of 6 µm with a sensing area size of 14.4 mm2 resembling a 9-turn MI biosensor is the optimal ratio yielding the maximum MI ratio of 238%, which is 70% larger than the 3- and 6-turn structures. The 3- and 6-turn MI biosensors exhibited similar characteristics where the MI ratio peaked at a similar value. Our results suggest that the MI ratio can be increased by increasing the sensing area size and film thickness rather than the number of turns. We showed that an optimal film thickness to sensing area size ratio is required to obtain a high MI ratio. Our findings will be useful for designing highly sensitive MI biosensors capable of detecting low biomagnetic signals.
Highlights
The MI biosensors were constructed based on fabrication parameters that included various thicknesses, sensing area sizes, and numbers of turns to investigate the impact of these parameters on the MI response
The results are presented and follow the impact of the fabrication parameters, including the number of turns taken by the film, film thickness, and size of the film sensing area
The MI biosensor consisted of comprised of nm chromium/copper (Cr/Cu)/NiFe/Cu/NiFe/Al2 O3 /Cr/Au films, where the NiFe/Cu/NiFe served as a sandwich magnetic material
Summary
Technological demands have contributed to the development and existence of the many types of magnetic sensors When developing these sensors, a combination of parameters must be considered for each specific application. A combination of parameters must be considered for each specific application These parameters include the external applied magnetic field, linearity, hysteresis, stability, portability, noise, power consumption, size, and cost [5,6,7,8,9,10,11]. Among these sensors are magneto-impedance (MI) biosensors, which are based on the magneto-impedance effect
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