Infrared Retroreflective, Visible Absorbing, and Electrostatically Adhesive Microsphere Taggants

MO-SCI Corporation and the Missouri University of Science & Technology (MST-formerly University of Missouri-Rolla) propose to develop low cost, IR retro-reflective (800 nm - 2800 nm), visible absorbing glass microspheres for ubiquitous spectroscopic tagging through our innovative material design, fabrication and characterization technologies. These glass microspheres of any size (e.g., 20 - 100 microns, diameter) absorb visible light and, thus, are minimally visible to the unaided human eye. The refractive index of the glass microspheres will be tailor-designed to allow a maximum retro-reflection in the IR region and, thus, can be easily spotted using a man-portable IR viewing device. We will also coat the microspheres with a layer that is strongly negative in the triboelectric series such as saran. The coating will increase the electrostatic attraction of the microbeads to human skin, hair, and commonly worn clothing fabrics. Daytime detection (e.g., on a sunny day) of the IR retro-reflective glass microspheres is possible with gated illumination and lock-in amplification techniques.