A remote query magnetoelastic pH sensor

A remote query magnetoelastic pH sensor comprised of a magnetoelastic thick -film coated with a mass-changing pH-responsive polymer is described. In re sponse to a magnetic query held the magnetoelastic sensor mechanically vibr ates at a characteristic frequency that is inversely dependent upon the mas s of the attached polymer layer. As the magnetoelastic sensor is magnetostr ictive the mechanical vibrations of the sensor launch magnetic flux that ca n be detected remotely from the sensor using a pickup coil. The pH responsi ve copolymer is synthesized from 20 mol% of acrylic acid and 80 mol% of iso -octyl acrylate and then deposited onto a magnetoelastic film by dip-coatin g. For a 1 mum polymer coating upon a 30 mum thick Metglas [The Metglas all oys are a registered trademark of Honeywell Corporation. For product inform ation see: http://www.electronicmaterials.com:80/businesses/sem/amorph/page 5_1_2.htm.] alloy 2826MB magnetoelastic film between pH 5 and 9 the change in resonant frequency is linear, approximately 285 Hz/pH or 0.6%/pH. The ad dition of 10 mmol/l of KCl to the test solution decreases the sensitivity o f the polymer approximately 4%. (C) 2000 Elsevier Science B.V. All rights r eserved.