The Armor Sensor is a development of the Hartman Interferometer which was the creation and patent(s) of Nile F. Hartman while at GTRI (Georgia Technology Research Institute)} in Atlanta GA. Dr Hartman continues to be closely involved in this journey. It is developed to be available for use case specific customization and evaluation as a hand held or worn device.
Interferometric technology can detect extremely small differences in the phase of coherent light between two optical paths, and be used to detect specific analytes in liquid or aerosol environments. Armor is reducing the size of this proven technology from a briefcase to smaller than a cell phone.
The Armor biological/chemical sensor is multi-‐channel and can respond to several completely different analytes on a single sensor (assay) chip, or provide higher confidence by orthogonal measurements of a single analyte. Each sensor has its own built in power supply and wireless communication link, so sensors could be used remotely and at varying points in a detection system without concern for wiring or interconnects. These sensors have shown to have typical sensitivity for biological organisms to a single colony forming unit (CFU), or to chemicals at parts per billion. The Armor Biological/chemical sensor does NOT use a spectrum analysis approach. Each sensor channel can be custom tailored for a different targeted agent with a unique attachment mechanism. A variety of important chemical and biological analytes have been successfully tested with the Armor sensor technology including: E. coli, Salmonella, IgM, Campylobacter, Listeria, Yersinia pestis, anthrax (Sterne) spores, influenza virus, and mycobacterium. These biological analytes were all measured in an aqueous environment.
The Armor sensor can be used as a remote handheld bio-‐agent sensor or as a laboratory instrument. Armor has a development program to increase the number of analytes and the attachment chemistry with the expectation that aptamers can be introduced in place of antibodies for microbes to provide direct performance measurement in representative environmental conditions (temperature & humidity) encountered in the field. In the field of contagious diseases, gene expression holds great promise as a marker for early and rapid diagnosis. Armor has a test protocol for sample collection in field measurements.
The Armor sensor uses advanced optics that provide greater stability, increase in the number of sensing channels, and facilitate smaller size, weight, and/power than competing devices . The Armor sensor is a robust real-‐time sensor system for the detection and quantification of a wide variety of biological and chemical agents (list in Tables 1 & 2).
The Armor device can simultaneously measure up to 30 analytes (note: Herein we refer to an analyte as a biological or chemical constituent that is of potential interest as an organism, bio-‐toxin, organic chemical compound, or other compounds such as explosives, genetic material, etc.), and could report these back to a collection point in real time using encrypted cell phone technology. The sensor provides a direct, real-‐time measurement without the need for additional steps as is usually required in most bio-‐assays.
Interferometric Sensor Block Diagram
The sensor system block diagram is shown here. The interferometer uses the evanescent field generated by a propagating optical beam in a waveguide to probe changes in the sensing film deposited on the waveguide surface. When a reaction or interaction occurs in the sensing film, a signal associated with that change can be measured by monitoring the fringe movement resulting from the combination of the sensing arm with an unaltered reference arm, and detects, identifies, and quantifies that a target analyte is present.
Interferometry is a technique used to measure one of three changes in a propagating light beam: path length, wavelength, or light speed along the path of propagation. The change is measured as a change in the phase of the light where the phase is dependent on the path length L, refractive index n, and wavelength by: = 2L n/. At the heart of the interferometric sensor is a channelized optical waveguide. Channelized optical waveguides have evanescent fields sensitive to index of refraction changes in the volume immediately above (up to 5000 Å) the surface.
Chemical or physical interactions at the surface of the sensing film change the index of refraction causing the propagating light phase to change in a direction opposite to that of the index change. A target agent coupling with a recognition element within this region provides the basis for the sensor response. A coherent beam of light (laser) is divided and coupled into the waveguide using a coupler fabricated in the substrate layer under the waveguide. One of these beams is sent through the waveguide and its evanescent field interacts with target agents in a test strip altering the phase in the waveguide and generating an immediate response. To measure this response, the other beam, passing through a reference strip adjacent to the sensing strip, is optically combined with the sensing beam
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