Development and Application of Magnetoacoustic Remote Query Environmental Sensors

This proposal seeks support for the development and application of a new remote query sensor technology based upon changes in the resonant frequency of free-standing magnetoelastic thick films. The work builds upon, complements, and helps extend the chemical sensor oriented research the co-Pis are actively involved with. Magnetoelastic sensors are comprised of ribbon-shaped thick-films ofmagnetostrictive, magnetoelastic amorphous metallic glass. In response to a time varying magnetic field magnetoelastic sensors efficiendy translate magnetic energy into elastic energy which, in turn, acts to mechanically deform the material. This mechanical deformation is greatest along the length of the sensor, and demonstrates a resonance the frequency of which is inversely proportional to the length of the sensor. Since the material is also magnetostrictive the mechanicaJ deformation acts to generate magnetic flux that can be detected through the use of a remotely located pickup coil. Furthermore, due to the high degree of surface roughness of the sensor the mechanical deformation launches an acoustic wave perpendicular to the basaJ plane of the sensor that can be detected remotely using a microphone. Hence the sensors can be monitored magneticalIy or acousticaly, as dependent upon the sensing application. The sensors are passive, responding to the interrogation field; therefore no internal power supply such as a battery is needed. No direct physicaJ connections to the sensor, or speciaJ orientation alignments, are required to obtain sensor information, consequendy the sensors can be monitored from within opaque or metallic enclosures such as food packages or people. It has recendy been demonstrated [see attached paper] that the resonant frequency of a magneto elastic sensor shifts in response to several different environmentaJ parameters including pressure, temperature, viscosity, inter-faciaJ molecular bond and, very importantly, when used in combination with a mass changing, chemicalIy responsive layer chemicaJ anaJyte concentrations. Application of magnetoelastic sensors to remote query chemical sensing has been demonstrated using a glucose responding polymer and a Ti02 humidity responsive ceramic thin film. Changes in the resonant frequency of a magnetoelastic sensor have been measured in response to a differentiaJ mass loading below 0.5 nglmm2. Ribbon-like sensors of such materiaJs, approximately S mm x 3S mm x 30 IJ.ID,are widely used as identification markers; not only can these sensors be easily monitored over a range of meters, but their low unit cost allows for use on a disposable basis. One detecting unit can serve an unlimited number of sensors, hence the sensor technology would be ideaJly suited for monitoring contamination of foodstuffs through sensing for CO2 levels, moisture levels in seaJed containers, CO and CO2 levels in closed air spaces, in-vivo measurement of gastric pH and pressure, etc. Within the scope of this program, the sensor technology will be moved beyond initiaJ proof-of-concept measurements to enable simultaneous remote query measurement of different environmental parameters, from a miniature platform (= S mm x 2 mm x 10 ,.un), at distances ranging from centimeters to meters. Using sol-gel methods the magnetoelastic sensors will be coated with thin «0.2 ,.un), nanoporous layers of ceramic Si02, Zr02, and A1203 for simultaneous, in-situ, real-time measurement of humidity, and partial pressures of catbon monoxide and carbon dioxide (three separate coated magneto elastic sensors are required for simultaneous measurement of the three parameters). The pore size of the ceramic layers will be controlled through the magnetic biasing of the magnetoelastic sensor material during coating. By virtue of their high surface areas, as high as 6S0m2/g, many more solutes can be adsorbed on the surface of these nanoporous films than would otherwise be absorbed onto, for example, a polymeric film. The E/PO proposal involves a month-long educational outreach workshop, to be held each summer, in which undergraduate science students from Kentucky State University (KSU), Kentucky's only Historically Black University (HBU), work in the laboratories of the co-Pis, with a KSU faculty mentor, in a project tearn format Ideally, the educationaJ outreach workshop will encourage the students to pursue advanced degrees in sensor-related fields. Recruiting of the KSU students will be done in collaboration with Professor R. Shahidain, a KSU professor in the Science and Mathematics Department, who will also help run the outreach program/workshop.