A low-cost sensor technology, called Chemical Identification by Magneto-Elastic Sensing (ChIMES), uses target response materials (TRMs) as actuators in magneto-elastic (M-E) sensors (Figure 1).

Figure 1. Conceptual drawing of the Chemical Identification by Magneto-Elastic Sensing (ChIMES) sensor.

TRMs can come from many classes of chemical and biochemical compounds, with many degrees of selectivity. TRMs with strong affinities for specific targets can be used individually, while TRMs with distributed selectivity can be formed into arrays with an artificial neural network or other artificial-intelligence-based tools used for analysis and interpretation. The magneto-elastic components are amorphous ferromagnetic alloys with high permeability and very low coercivity. When a TRM encounters a target, it imposes forces that change the magnetic properties of the alloy in ways that can be detected with an excitation-detection coil set.

Figure 2. A four-TRM array.

ChIMES includes a ferromagnetic metal and a molecular recognition reagent coupled to the ferromagnetic metal. The molecular recognition reagent is operable to expand upon exposure to vapor or liquid from the target material such that the molecular recognition reagent changes a tensile stress upon the ferromagnetic metal. The target material is detected based on changes in the magnetic switching characteristics of the ferromagnetic metal caused by the changes in the tensile stress.

The sensor can detect anything for which TRMs can be identified or developed. It is capable of untethered communication through a nonmetallic or thin metallic barrier. ChIMES can be miniaturized, and is energy-efficient enough for power with onboard batteries. Shape, size, and appearance can be tailored to a specific need. ChIMES is suitable for both overt and covert applications, and can detect multiple and variable targets simultaneously with modular TRMs. The sensor is much less expensive than techniques such as gas chromatography.

Applications for ChIMES include explosives or taggants; chemical and biological warfare agents and precursors or byproducts of their manufacture; exhaled gas constituents for health diagnostics and drug detection; toxic industrial chemicals and materials; food freshness and safety; volatile organic compounds; and other airborne and waterborne pollutants.

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