A thin wire—thinner than a human hair—could someday help prevent surgical snafus, forgery, shoplifting, product tampering, and even chemical or biological hazards. The highly versatile amorphous glass-covered microwire could be used in multiple ways as sensors and markers like radio frequency identification (RFID) tags.
The microwire, the focus of a Cooperative Research and Development Agreement (CRADA) between the Y-12 National Security Complex in Oak Ridge, Tennessee, and Demodulation, Inc., in Westwood, New Jersey, recently caught the attention of a famous medical clinic concerned with the accounting of 400-500 sponges during complex surgeries. Today's accountability methods require painstaking before-and-after sponge counts to avoid leaving one in a patient.
When the counts differ, a large X-ray machine is wheeled in. Y-12 researchers demonstrated that a sponge containing an amorphous microwire could be detected as far as 3 inches away. The investigators are now attempting to increase that to 12 to 18 inches. The microwire's advantages: A magnetic field is safer than X-rays, and a small handheld detector could replace the bulky X-ray machine.
Y-12's interested in microwires' potential use as sensors. An ideal feature is the microwire's freedom from a wired connection for power or collection of data. A microwire sensor embedded in a nonferrous, or ironfree, item can be excited, and its response can be measured from a distance. "Most sensors require a battery or a power connection; the amorphous microwires do not," said Neville Howell, manager of the Y-12 Control and Sensor Systems Section.
Microwires have magnetic domains that switch when alternating magnetic fields are nearby, "and there are ways to detect the domain switching without physically connecting to the microwire." Thus, microwires act as sensors without connecting wires for power or data collection.
Amorphous microwires are also sensitive to stress. Amorphous refers to their disordered atomic structure that provides high tensile strength, which reacts to subtle changes in tension, a standard indicator for many sensing applications.
Y-12 researchers found that changes as small as 0.0004-pound forces can be resolved. Coat a microwire with a substance that reacts to a hazardous chemical or biological agent, and a change in the wire's tension could reveal the presence of that hazard in the environment. The microwire's sensitivity to stress, and to temperature, could also enhance protective seals on containers, a potential boon to the food and pharmaceutical industries, as well as Y-12.
The microwires are detected either from radio frequency (RF) signals or by magnetic coil pickup.
In the RF method, the transmitter and receiver can be a lengthy distance from the microwire, depending on the transmitter's power level.
However, the RF cannot penetrate certain items that contain microwiretagged contents.
The magnetic coil pickup method penetrates aluminum, stainless steel and other nonferrous containers, but the coil's detection distance is currently less than 3 inches.
Other applications include identification tags. Microwires, which can be mass produced for less than 1 cent apiece, have unique signatures, like snowflakes.
Incorporating magnetic material, adding stress variations, and controlling location can change detection signatures. Microwires, manipulated to store digital information and combined with bar codes affixed to their glass coating, could kibosh counterfeiters. "You can put 32 microwires in an area of a quarter and have 4 billion serial number options," Howell explained. "We've proven a technique for encoding multiple bits of information on surfaces the size of a credit card or smaller," said participating Y-12 intern Zach Nienstedt. "When microwires are parallel to each other on a drive coil or sense coil, you can read each individual wire and encode information very securely in that setup."
For numerous sensor applications, Y-12 researchers are developing techniques to improve standoff detection distance and increase sensitivity for data retrieval.
Uses for the device are expanding and spurring interest from government agencies and industry.
As for Demodulation, Inc., founder and CEO Jim O'Keefe described the collaboration with Y-12 as "exceptional, extremely positive" and an example of "good applied engineering in which Y-12 has clearly demonstrated the performance characteristics of our technology. We're looking at the advancement of materials and a new generation of technology."
Microwire sensing provides "a very rich technological base that can generate a lot of new businesses….Y-12 is looking at specific material property sets for specific applications, and we are very pleased with the results."
More info: Tammy Graham, 865-574-2214, grahamtb@y12.doe.gov
