ATI Partners to Deliver Passive RFID Sensor

Jun 30, 2011American Thermal Instruments (ATI), a Dayton, Ohio-based manufacturer of temperature-sensing RFID tags and other temperature-based products, such as forehead thermometers, has established a license with Bob Kauffman, a researcher at the University of Dayton Research Institute, to develop new passive high-frequency (HF) and ultrahigh-frequency (UHF) RFID sensors that have an innovative trigger mechanism.

ATI plans to turn Kauffman's design into a finished product within 18 months or less. The company currently sells active HF 13.56 MHz RFID tags, marketed as LOG-IC tags, with an integrated temperature sensor, but tags built on the SMART (Status and Motion Activated Radiofrequency Tag) design would be passive, and thus less expensive.

"We worked out a deal where we will license the technology, and ATI will use it for applications in the areas we service," says Randal Lane, ATI's president. The technology will be employed primarily to monitor perishable foods and temperature-sensitive drugs or chemicals, and companies in other industries will be able to sublicense the technology from ATI as well.

Kauffman developed and prototyped the tag design in response to a grant from the Federal Aviation Administration (FAA). Following the 1996 crash of Trans World Airlines (TWA) Flight 800, the FAA assigned a team of researchers to investigate the accident's cause.

The team, which included Kauffman, established that exposed fuel-sensor wires, which had become unmoored and lost insulation during the plane's lifetime, had likely sparked an explosion. With the help of an additional $200,000 FAA grant, Kauffman set out to develop technologies that could prevent further such accidents from occurring.

To that end, Kauffman designed a clamp, made to bundle and secure wires within a plane, that contains an integrated passive RFID inlay. A push-button switch keeps a circuit inside the tag's chip from closing, thereby creating an electrical bypass that prevents that tag from transmitting a radio signal. As long as the clamp is secure, the tag remains unreadable. But should the clamp fail and open up, the push-button bypass would break, closing the circuit and allowing the tag to transmit its identity to an RFID reader. In that way, plane operators could identify which clamp had failed.

The wire clamp—which is still in development, and has yet to be tested outside Kauffman's lab—led the researcher to file a patent describing the process of using an electrical bypass to render an RFID tag inactive until some force(whether a jolt, a temperature increase or drop, or some other "abnormal" event)breaks the bypass, making the tag readable.

To show ATI that the SMART design could be utilized to monitor temperatures, Kauffman produced a prototype tag in which the electrical bypass was composed of silver powder and beeswax. Once the tag was exposed to high temperatures of around 100 degrees Fahrenheit (38 degrees Celsius), the bypass melted and the tag was then able to conduct an RF signal. ATI will use any number of materials to design the bypass, Kauffman says, depending on the temperature threshold being monitored in a particular application. Many different low-melting alloys could be used, he notes.

ATI will continue to manufacture and sell its LOG-IC tags, and plans to offer the passive tags to customers that do not require the level of detail and data logging that LOG-IC tags provide (full logs are stored on the tag's memory, and are downloaded once a shipment is received).

The passive tags—which Lane says will likely be made available in both a UHF Gen 2 model, as well as an HF version—will fit into the company's product lineup, between ATI's basic non-RFID temperature-monitor patches, which provide visual indicators once a temperature threshold has been exceeded, and the active RFID temperature data loggers. The RFID interface will enable customers to root out products that have fallen below safe temperature levels, without having to physically handle each box or pallet in order to read the indicator. According to Lane, ATI hopes to sell the passive tags for under $2 apiece.

The decision to create the SMART design with a passive tag was born of necessity, Kauffman says. "As we started getting into [researching RFID], it looked like it would have to be active tags attached to sensors," he states. But a single airplane would require a huge number of clamps, so the cost and complexity of utilizing active tags to monitor and track them would not be feasible.

Therefore, Kauffman turned his attention to passive tags. "We asked, why can't we make the tag be the sensor?" he says. "That's where the SMART sensor idea came from."

As evident with the clamp design, temperature variance is just one of many forces that could break a tag's electrical bypass—for instance, an impact over a set force could do so as well. As such, one potential application for the tag would be to track the impact sustained by children's helmets—for example, those used by youth football leagues.

"We are looking to sublicense the technology to companies that do things better than we could," Lane says.