This paper presents a comprehensive review of magnetoelastic environmental sensor technology; topics include operating physics, sensor design, and illustrative applications. Magnetoelastic sensors are made of amorphous metallic glass ribbons or wires, with a characteristic resonant frequency inversely proportional to length. The remotely detected resonant frequency of a magnetoelastic sensor shifts in response to different physical parameters including stress, pressure, temperature, flow velocity, liquid viscosity, magnetic field, and mass loading. Coating the magnetoelastic sensor with a mass changing, chemically responsive layer enables realization of chemical sensors. Magnetoelastic sensors can be remotely interrogated by magnetic, acoustic, or optical means. The sensors can be characterized in the time domain, where the resonant frequency is determined through analysis of the sensor transient response, or in the frequency domain where the resonant frequency is determined from the frequency-amplitude spectrum of the sensor.

An aqueous sensor network is described consisting of an array of sensor nodes that can be randomly distributed throughout a lake or drinking water reservoir. The data of an individual node is transmitted to the host node via acoustic waves using intermediate nodes as relays. Each node of the sensor network is a data router, and contains sensors capable of measuring environmental parameters of interest. Depending upon the required application, each sensor node can be equipped with different types of physical, biological or chemical sensors, allowing long-term, wide area, in situ multi-parameter monitoring. In this work the aqueous sensor network is described, with application to pH measurement using magnetoelastic sensors. Beyond ensuring drinking water safety, possible applications for the aqueous sensor network include advanced industrial process control, monitoring of aquatic biological communities, and monitoring of waste-stream effluents.

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