Explosive Detection Instrument
With an estimated 100 million mines and countless millions of acres of land contaminated with unexploded ordnance (UXO) worldwide there is a need for sensor systems and methods that can detect and identify large and small explosive objects buried in soil. In addition, during armed conflict, there is a need for mine detection and neutralization in real-time or near real-time.
The present invention provides a simple, relatively low cost, stand-alone, portable device that can be used virtually anywhere including close proximity to humans. The invention generates an image of buried land mines that aids in reducing false positives, identifying mine type, and recognizing mine orientation.
While the sensor element of the detector of the invention can take many forms, a preferred embodiment uses a molecularly imprinted polymer (MIP) which is generally described as a plastic cast or mold of the molecule of interest, where recognition is based on shape, much like a lock and key. MIPs are made by adding the molecule of interest to a solution of binding molecules that can be chemically incorporated into a polymer. These binders usually have an affinity for the target and form a complex.
The interactions that hold these complexes together include II--II interactions, hydrogen bonding, metal-ligand binding, and even covalent bond formation, but they must be reversible. The binder must also have a chemical functionality that allows it to be irreversibly bound to polymers. Vinyl groups are a common functional group used to prepare many polymers, e.g., polyethylene, polystyrene, polyvinylalcohol, and polyvinylchloride. The target-binder complex is dissolved in excess monomer (for example, styrene) and possibly other additives such as a cross-linker and porogens (solvents).
In a typical sensor fabrication, a solid plastic mass, consisting of the matrix and binder, is obtained which is chemically bound to the polymer/cross-linker matrix and the target molecule. Removal of the target is possible since it is reversibly bound to the binder. The cavity it leaves behind is permanently shaped like the target.
The explosive embodiment of the detector of the invention utilizes an array of MIP coated, bifurcated fiber optic cables to form an image of a target molecule source to detect and identify trace levels of explosive material emanating from land mines. Individual sensor fiber assemblies, each with a calibrated airflow, are used to expose the fibers to the target molecule. The detector energizes a dedicated excitation light source for each fiber, and, through a detector element, e.g., a filter and photodiode, simultaneously reads and processes the intensity of the resulting fluorescence that is indicative of the concentration of the target molecule. Processing electronics precisely control the excitation current, and measures the detected signal from each filter and photodiode.
A computer with display processes the data from each calibrated detector element to form an image of the target molecule source that can be used to identify the source even when low level contamination of the same molecule is present. The detector can be used to detect multiple targets by varying the MIP coating. Where mere detection of the presence of a target molecule is satisfactory, the array can be reduced to a single fiber assembly for each target molecule. The detector can be modified to detect other (non-explosive) materials by changing the MIP coating and selecting appropriate light sources, photodetectors, and filters.
Patent Status: U.S. patent(s) 6967103 issued.CONTACT: