Scattering of Microwaves by a Passive Array Antenna Based on Amorphous Ferromagnetic Microwires for Wireless Sensors with Biomedical Applications.

Alberto Moya,Diego Archilla,Elena Navarro,Antonio Hernando,Pilar Marín

doi:10.3390/s19143060

Abstract

Co-based amorphous microwires presenting the giant magnetoimpedance effect are proposed as sensing elements for high sensitivity biosensors. In this work we report an experimental method for contactless detection of stress, temperature, and liquid concentration with application in medical sensors using the giant magnetoimpedance effect on microwires in the GHz range. The method is based on the scattering of electromagnetic microwaves by FeCoSiB amorphous metallic microwires. A modulation of the scattering parameter is achieved by applying a magnetic bias field that tunes the magnetic permeability of the ferromagnetic microwires. We demonstrate that the OFF/ON switching of the bias activates or cancels the amorphous ferromagnetic microwires (AFMW) antenna behavior. We show the advantages of measuring the performing time dependent frequency sweeps. In this case, the AC-bias modulation of the scattering coefficient versus frequency may be clearly appreciated. Furthermore, this modulation is enhanced by using arrays of microwires with an increasing number of individual microwires according to the antenna radiation theory. Transmission spectra show significant changes in the range of 3 dB for a relatively weak magnetic field of 15 Oe. A demonstration of the possibilities of the method for biomedical applications is shown by means of wireless temperature detector from 0 to 100 °C.

Highlights

Since the first publications on wire-based biosensor prototypes [1], many researchers have focused their efforts to develop soft magnetic materials and to understand its properties under the point of view of technological applications [2]
These works focus on both methodological and basic development and report experimental evidences of the dependence of microwave scattering by a single microwire on its magnetic permeability; an effect that is strong enough to be labeled as an effect of the giant magnetoimpedance (GMI)
We show that for appropriate distances between microwires in the arrangement, they behave like a passive ferromagnetic array antenna

Summary

Introduction

Since the first publications on wire-based biosensor prototypes [1], many researchers have focused their efforts to develop soft magnetic materials and to understand its properties under the point of view of technological applications [2]. [25,26,27,28,29], some research has been oriented to understand the effect of GMI on the scattering of microwaves by a single AFMW These works focus on both methodological and basic development and report experimental evidences of the dependence of microwave scattering by a single microwire on its magnetic permeability; an effect that is strong enough to be labeled as an effect of the GMI. Some of these works have shown different approaches by means of microwires forming arrays or buried in different types of matrix, searching to enhance their sensitivity as a GMI [30,31,32]

Methods

Results

Conclusion