Simple Device to Measure Pressure Using the Stress Impedance Effect of Amorphous Soft Magnetic Thin Film

Abstract

<jats:p>A simple micro-machined pressure sensor, based on the stress-impedance (SI) effect, was fabricated herein using typical micro-fabrication technologies. To sense pressure, a 1-µm thin, soft magnetic metallic film of FeSiB was sputtered and used as a diaphragm. Its electrical response (impedance change) was measured under pressure in a frequency band from 5 to 500 MHz. A lumped-element equivalent electric circuit was used to separate the impedance of the soft magnetic metal from other parasitic elements. The impedance change clearly depended on the applied pressure. It was also shown that the impedance change could be explained by a change in relative permeability, according to the theory of the SI effect. The radial stress in the diaphragm and the relative permeability exhibited a linear relationship. At a measurement frequency of 200 MHz, the largest sensor response, with a gauge factor of 385.7, was found. It was in the same order as the conventional sensors. As the proposed device is very simple, it has the potential for application as a cheap pressure sensor.</jats:p>

Micromechanical Force Sensor Using the Stress–Impedance Effect of Soft Magnetic FeCuNbSiB

“…At a gas flow rate of 15 sccm, the intrinsic stress was close to 0 Pa. To confirm the structure of the film, X-ray diffraction (XRD) was used. The fabrication process was similar to the process described in [27]. The structuring of the metal alloy was performed by ion-beam milling using OFPR-800 200cp (Tokyo Ohka Kogyo).…”

“…Most of the investigated devices are rather large in size. Although applications other than as a strain gauge (e.g., for structural health monitoring, pressure sensors, or force sensors) have been proposed in the past [25,26], recently, a practical, small pressure sensing device made entirely using microtechnologies was presented for the first time to demonstrate the feasibility of MEMS sensors using the SI effect [27]. A GF of 385.7 was reported.…”

Giant Stress-Impedance Effect in CoFeNiMoBSi Alloy in Variation of Applied Magnetic Field

“…The SI effect is, thus, a new addition to a broad series of magnetomechanical effects [ 22 ], some of which were first observed in the first half of the nineteen century, and are researched to this day due to high sensitivity of various experimental sensors, which can be obtained in newly developed materials [ 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. The most known of the magnetomechanical effects are magnetostrictive and Villari effects [ 33 ], the latter leads to a change in magnetic permeability due to the mechanical stress, by inducing temporary magnetic anisotropy in stress direction [ 34 ].…”