Magnetoelectric cantilever sensors under inhomogeneous magnetic field excitation

Abstract

The behavior of strain-coupled composite magnetoelectric cantilever sensors under excitation with an inhomogeneous magnetic field is investigated. We consider a local excitation generated by a ring-shaped copper coil with one winding, variably positioned around the sensor. 3D finite-element-method simulations of the sensitivity along the longitudinal sensor axis are conducted and compared to the experimental results. The investigated sensor consists of a 2 µm thick magnetostrictive layer [(Fe90Co10)78Si12B10] and a 2 µm thick AlN piezoelectric layer on the opposite sides of a 350 µm thick silicon cantilever of 26.25 mm length and 2.45 mm width. The sensitivity along the sensor axis is investigated for three different frequencies—one below the resonance frequency, one at resonance, and one above resonance. A rich position-dependent sensitivity behavior is observed in simulations and experiments with a maximum sensitivity at ∼4 mm from the fixed end of the cantilever for all three frequencies. Below and at the resonance frequency, a monotonously decreasing sensitivity is observed toward the free end of the cantilever. For the frequency above resonance, we observe a position of zero sensitivity at ∼17 mm from the fixed end and a subsequent second maximum of sensitivity. We attribute the zero sensitivity to the destructive interference of local excitation and resonance effects.

A Combined Magnetoelectric Sensor Array and MRI-Based Human Head Model for Biomagnetic FEM Simulation and Sensor Crosstalk Analysis

“…We designed and implemented the ME sensor based on the ME sensor models from our previous work [ 26 , 27 ]. Each sensor consisted of a substrate layer of silicon with 26.25 mm length, 2.45 mm width, and 300 µm thickness, a magnetostrictive layer of FeCoSiB with 22.90 mm length, 1.80 mm width, and 20 µm thickness, and a piezoelectric layer of aluminum nitride (AlN) with 25.60 mm length, 1.60 mm width, and 20 µm thickness.…”

“…A linearized material model was used at the sensor’s small-signal working point. Details of the applied boundary conditions and physical properties of the three layers are described in our previous work [ 26 , 27 ].…”

“…A linearized material model was used at the sensor's small-signal working point. Details of the applied boundary conditions and physical properties of the three layers are described in our previous work [26,27]. The mathematical model and physical properties of cantilever ME sensors consisting of ideal and slipless composite layers are governed by systems of differential and constitutive equations which are characterized in detail in previous studies [30,[34][35][36][37][38].…”

“…However, the respective sensor systems for such applications are often not jointly evaluated at all, or simplified to point [ 24 ] or circular magnetometers [ 25 ]. However, ME sensors are not of a negligible size and their geometry plays a role in the sensitivity of measurements [ 26 ]. Therefore, the study framework presented in this work is necessary to simulate sensors and the head or throat in a single FEM model.…”

A Combined Magnetoelectric Sensor and Human Head Model for Biomagnetic FEM Simulations

“…While in past studies, the performance characterization of ME sensors has often been conducted under simplified homogeneous magnetic field excitation, this work focuses on investigating sensor behavior under the influence of inhomogeneous magnetic fields in order to more accurately model sensor behavior in application-oriented scenarios. Our theoretical investigation is based on the approach of threedimensional (3D) finite element method (FEM) simulations and introduces a combined simplified three-shell human head and an array of three orthogonal ME sensors in a single FEM model [11]- [13]. The ME sensor array is positioned inside an air volume surrounding the human head, which in turn contains one or multiple electric point dipole sources.…”