A magnetostatic-coupling based remote query sensor for environmental monitoring

A new type of in situ, remotely monitored magnetism-based sensor is present ed that is comprised of an array of magnetically soft, magnetostatically-co upled ferromagnetic thin-film elements or particles combined with a chemica lly responsive material that swells or shrinks in response to the analyte o f interest. As the chemically responsive material changes size the distance between the ferromagnetic elements changes, altering the inter-element mag netostatic coupling. This in turn changes the coercive force of the sensor, the amplitude of the voltage spikes detected in nearby pick-up coils upon magnetization reversal. and the number of higher-order harmonics generated by the flux reversal. Since the sensor is monitored through changes in magn etic flux, no physical connections such as wires or cables are needed to ob tain sensor information, nor is line of sight alignment required as with la ser telemetry; the sensors can be detected from within sealed, opaque or th in metallic enclosures.