IEEE members at Drexel University, in Philadelphia, are developing transparent antennas that can be customized along with inkjet-printable RF components to form circuits applicable to all sorts of things. These include tracking military troop movements, monitoring health conditions, preventing shoplifting, and warning of impending car collisions. Those are just a few of the applications envisioned by a trio of engineering professors at the university.
The components and the antennas are created by a printing technique that applies a coating of conductive polymers onto glass, plastic, fabrics, or other materials. The process is suited for printable components including transmission lines, capacitors, inductors, RF switches, tuning networks, and complete RF subsystems, along with the antennas.
With the university’s support, the team recently formed MetaTenna, in Exton, Pa., and named the product line SheerFlex.
“Our goal is to make possible ubiquitous and unobtrusive high-speed wireless-communications links using transceivers fabricated from unconventional materials on nontraditional substrates,” says Senior Member Kapil Dandekar.
Dandekar, an associate professor and assistant department head of electrical and computer engineering, is director of the Drexel Wireless Systems Laboratory. His colleagues at MetaTenna are IEEE Senior Member Adam Fontecchio, an associate professor of electrical and computer engineering and an associate dean of engineering for undergraduate affairs, and IEEE Senior Member Timothy Kurzweg, an associate professor of electrical and computer engineering who is also assistant dean of engineering.
The printing technique works by loading liquid polymer into basically a large ink-jet printer, Kurzweg says. The droplets deposited on a substrate can form an antenna, which is baked in an oven, creating a conformable, conductive polymer. The transparent antennas can range in size, depending on the frequency of the application. They’ll operate at standard radio frequencies used by cellphones and other wireless applications, and are safe to wear, according to Fontecchio, but more testing is required. And they are washable.
Initial funding for the project came from the U.S. Army Communications-Electronics Research, Development, and Engineering Center, in Fort Monmouth, N.J. After this effort concluded, the Drexel team was interested in exploring whether the printed components and their transparent antennas can be worn on a soldier’s uniform or placed on a Humvee as a communication system for secure transmissions.
“The beauty of the antennas and the ink-jet printing process is that the frequency can be changed every day—or on the fly, if you will,” Kurzweg says. “The antenna can also be adapted to different environmental conditions. This allows for better communication, over longer distances, and at lower power. The other advantage is that you get a more secure system because the antennas, and their operating frequencies, are being changed physically. They aren’t a piece of software that can be cracked by the enemy.”
The team also is developing circuits for real-time telemetry of soldiers’ vital signs. For example, commanders might want to know whether a soldier’s heart rate is changing, whether he’s overheated or cold, or how many steps he’s taken. According to Kurzweg, the circuits can be embedded along with real-time sensors sewn into clothing to monitor these conditions.
MEDICAL SENSORS, TOO
Military applications aren’t the only things being worked on. The wearable components can be used for civilian purposes such as medical tests. The researchers are collaborating with Drexel’s nursing school and its College of Media Arts to design an undershirt to be worn by pregnant women that could track and store a fetus’s heart rate. The garment would replace wearable monitors that are far bulkier.
The antennas also can be used as RFID tags to replace simple bar codes. To combat shoplifting, passive RFID tags with their antennas and security codes could be printed on a garment, replacing larger security tags.
“These antennas could be placed right on the article of clothing as it moves through the manufacturing line,” Kurzweg says.
Several potential applications on vehicles are foreseen for the antennas. They include placing the antenna on a windshield for electronic toll collection, printing them on the vehicle roof as an uplink for satellite radio, or laminating an antenna in the car to boost cellphone reception between cell towers. Other ideas are to wirelessly integrate the antennas with a car’s proximity sensor system to alert drivers when they are getting too close to another car or to the side of a building. They could also warn of an imminent collision.
Kurzweg says MetaTenna is within 18 months of producing a commercial product. The company has received business grants from the U.S. National Science Foundation, and has a patent pending.
The group is open to new partnerships and ventures. “There are a lot of applications we haven’t even thought of, and we’re very receptive to hearing ideas about new ones,” Fontecchio says.