NIST 'phantom material' may help improve metal detectors

To ensure that security at the nation's airports is as strong as it can be, metal detectors for detecting concealed weapons must be as sensitive as they can be. However, no one wants these devices to cause problems for innocent passengers using lifesaving personal medical electronic devices (PMEDs) such as cardiac pacemakers. The National Institute of Standards and Technology (NIST) soon may be able to help solve the dilemma.

Providing the solution to this problem may be a new, NIST-developed semisolid "phantom material" that can simulate the electromagnetic characteristics of different human body tissues over a range of frequencies. Created by researchers in NIST's Radio-Frequency Technology Division, the moldable material (a carbon black-silicone composite) could be embedded with PMEDs, and then sent through a metal detector to determine the effect of the generated magnetic fields on the function of pacemakers, hearing aids, infusion pumps and the like.

Currently, some metal detector manufacturers insert test objects in a liquid that mimics the conductivity of different body tissues, but the objects can shift within the liquid and produce varying readings. Additionally, many test liquids evaporate or are unstable over time.

The new NIST semisolid material can be made to match the conductivity of any body tissue and, because of its rigidity, keeps the PMEDs in a test sample fixed. This material can be made to emulate the electrical properties of a human for the frequencies over which walk-through and handheld metal detectors operate.

This research was funded by the Office of Science and Technology at the National Institute of Justice through NIST's Office of Law Enforcement Standards.

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