Wang Z.,Ohio State University |
Lee L.Z.,Ohio State University |
Psychoudakis D.,ElectroScience Laboratory |
Psychoudakis D.,Samsung |
Volakis J.L.,Ohio State University
IEEE Transactions on Antennas and Propagation | Year: 2014
A novel textile-based body-worn antenna covering the Global System for Mobile Communications/personal communications services/wireless local-area network frequency bands is presented. This antenna was made of densely embroidered metal-coated polymer fibers (e-fibers). These e-fibers are 15 μm thick and consist of high strength, flexible polymer cores with conductive silver coatings, providing mechanical flexibility and low loss at radio frequencies. When measured in free space, the textile antenna showed comparable performance to its copper counterpart, having ~2 dBi realized gain at all three bands. This textile antenna was simulated and measured on a full body phantom to determine the body's influence on antenna performance, including frequency detuning and pattern shadowing. The measured radiation pattern of the body-worn antenna matched well with simulation at various on-body locations for the three bands. Field measurements were also carried out by mounting the antenna onto the shoulder of a jacket, and using it to replace the one of a cell phone. We found that the communication quality using the body-worn textile antenna was equivalent to the best location of the original cell-phone antenna. Therefore, this textile-based antenna provided for a more reliable body-worn communication when mounted on the body's shoulder. © 1963-2012 IEEE.
Lee J.-F.,ElectroScience Laboratory
Proceedings - 2010 12th International Conference on Electromagnetics in Advanced Applications, ICEAA'10 | Year: 2010
The integral equation (IE) method is commonly used to model time-harmonic electromagnetic (EM) phenomena. One of the major challenges in its application arises in the solution of the resulting illconditioned matrix equations. Here, we introduce a new domain decomposition (DD) based iterative method for the IE solution of time-harmonic electromagnetic problems. There are two major ingredients in the proposed IE-DDM: (a) the method is a type of nonoverlapping DD method and provides a computationally efficient and effective preconditioner for the dense matrix equation from the IE method; and, (b) The presented method is very suitable for dealing with multiscale EM problems. Each sub-domain has its own characteristics length and will be meshed independently from others. Numerical results demonstrate superior performance of the IE-DDM. ©2010 IEEE.
News Article | April 15, 2016
Researchers who are working to develop wearable electronics have reached a milestone: They are able to embroider circuits into fabric with 0.1 mm precision -- the perfect size to integrate electronic components such as sensors and computer memory devices into clothing. With this advance, the Ohio State University researchers have taken the next step toward the design of functional textiles -- clothes that gather, store, or transmit digital information. With further development, the technology could lead to shirts that act as antennas for your smart phone or tablet, workout clothes that monitor your fitness level, sports equipment that monitors athletes' performance, a bandage that tells your doctor how well the tissue beneath it is healing -- or even a flexible fabric cap that senses activity in the brain. That last item is one that John Volakis, director of the ElectroScience Laboratory at Ohio State, and research scientist Asimina Kiourti are investigating. The idea is to make brain implants, which are under development to treat conditions from epilepsy to addiction, more comfortable by eliminating the need for external wiring on the patient's body. "A revolution is happening in the textile industry," said Volakis, who is also the Roy & Lois Chope Chair Professor of Electrical Engineering at Ohio State. "We believe that functional textiles are an enabling technology for communications and sensing -- and one day even medical applications like imaging and health monitoring." Recently, he and Kiourti refined their patented fabrication method to create prototype wearables at a fraction of the cost and in half the time as they could only two years ago. With new patents pending, they published the new results in the journal IEEE Antennas and Wireless Propagation Letters. In Volakis' lab, the functional textiles, also called "e-textiles," are created in part on a typical tabletop sewing machine--the kind that fabric artisans and hobbyists might have at home. Like other modern sewing machines, it embroiders thread into fabric automatically based on a pattern loaded via a computer file. The researchers substitute the thread with fine silver metal wires that, once embroidered, feel the same as traditional thread to the touch. "We started with a technology that is very well known--machine embroidery--and we asked, how can we functionalize embroidered shapes? How do we make them transmit signals at useful frequencies, like for cell phones or health sensors?" Volakis said. "Now, for the first time, we've achieved the accuracy of printed metal circuit boards, so our new goal is to take advantage of the precision to incorporate receivers and other electronic components." The shape of the embroidery determines the frequency of operation of the antenna or circuit, explained Kiourti. The shape of one broadband antenna, for instance, consists of more than half a dozen interlocking geometric shapes, each a little bigger than a fingernail, that form an intricate circle a few inches across. Each piece of the circle transmits energy at a different frequency, so that they cover a broad spectrum of energies when working together--hence the "broadband" capability of the antenna for cell phone and internet access. "Shape determines function," she said. "And you never really know what shape you will need from one application to the next. So we wanted to have a technology that could embroider any shape for any application." The researchers' initial goal, Kiourti added, was just to increase the precision of the embroidery as much as possible, which necessitated working with fine silver wire. But that created a problem, in that fine wires couldn't provide as much surface conductivity as thick wires. So they had to find a way to work the fine thread into embroidery densities and shapes that would boost the surface conductivity and, thus, the antenna/sensor performance. Previously, the researchers had used silver-coated polymer thread with a 0.5-mm diameter, each thread made up of 600 even finer filaments twisted together. The new threads have a 0.1-mm diameter, made with only seven filaments. Each filament is copper at the center, enameled with pure silver. They purchase the wire by the spool at a cost of 3 cents per foot; Kiourti estimated that embroidering a single broadband antenna like the one mentioned above consumes about 10 feet of thread, for a material cost of around 30 cents per antenna. That's 24 times less expensive than when Volakis and Kiourti created similar antennas in 2014. In part, the cost savings comes from using less thread per embroidery. The researchers previously had to stack the thicker thread in two layers, one on top of the other, to make the antenna carry a strong enough electrical signal. But by refining the technique that she and Volakis developed, Kiourti was able to create the new, high-precision antennas in only one embroidered layer of the finer thread. So now the process takes half the time: only about 15 minutes for the broadband antenna mentioned above. She's also incorporated some techniques common to microelectronics manufacturing to add parts to embroidered antennas and circuits. One prototype antenna looks like a spiral and can be embroidered into clothing to improve cell phone signal reception. Another prototype, a stretchable antenna with an integrated RFID (radio-frequency identification) chip embedded in rubber, takes the applications for the technology beyond clothing. (The latter object was part of a study done for a tire manufacturer.) Yet another circuit resembles the Ohio State Block "O" logo, with non-conductive scarlet and gray thread embroidered among the silver wires "to demonstrate that e-textiles can be both decorative and functional," Kiourti said. They may be decorative, but the embroidered antennas and circuits actually work. Tests showed that an embroidered spiral antenna measuring approximately six inches across transmitted signals at frequencies of 1 to 5 GHz with near-perfect efficiency. The performance suggests that the spiral would be well-suited to broadband internet and cellular communication. In other words, the shirt on your back could help boost the reception of the smart phone or tablet that you're holding - or send signals to your devices with health or athletic performance data. The work fits well with Ohio State's role as a founding partner of the Advanced Functional Fabrics of America Institute, a national manufacturing resource center for industry and government. The new institute, which joins some 50 universities and industrial partners, was announced earlier this month by U.S. Secretary of Defense Ashton Carter. Syscom Advanced Materials in Columbus provided the threads used in Volakis and Kiourti's initial work. The finer threads used in this study were purchased from Swiss manufacturer Elektrisola. The research is funded by the National Science Foundation, and Ohio State will license the technology for further development. Until then, Volakis is making out a shopping list for the next phase of the project. "We want a bigger sewing machine," he said.
Obeidat K.A.,ElectroScience Laboratory |
Obeidat K.A.,Brigham Young University |
Raines B.D.,ElectroScience Laboratory |
Rojas R.G.,ElectroScience Laboratory |
Strojny B.T.,ElectroScience Laboratory
IEEE Transactions on Antennas and Propagation | Year: 2010
This paper demonstrates a design procedure for frequency tunable reconfigurable antennas based on the application of reactive loads. Unlike other design procedures, antennas of arbitrary geometry can be tuned utilizing the proposed design framework. The design technique utilizes the theory of network characteristic modes to systematically compute reactive load values required to resonate any antenna at many frequency points in a wide frequency range. For simplicity, a 1.2 m dipole antenna is used to demonstrate the design procedure by tuning it at four loading ports along the antenna body. Both simulations and measurements demonstrate wide frequency tunability characteristics of the dipole input impedance (tunability range wider than 1:4) while preserving the radiation pattern and polarization at seven different frequency states. Lastly, a loaded PIFA is briefly examined as a more complex application of the procedure. © 2010 IEEE.
News Article | April 15, 2016
Wearable technology is becoming more ubiquitous. Fitbit wearers continuously check how many steps they’ve taken each day, researchers are designing wearables that monitor what one eats, and everyone can play secret agent by taking a phone call with their smartwatch. Researchers at The Ohio State University are working to advance the field of e-textiles, or clothes with the ability to transmit digital information. “We started with a technology that is very well known—machine embroidery—and we asked, how can we functionalize embroidered shapes? How do we make them transmit signals at useful frequencies, like for cell phones or health sensors?” said John Volakis, director of the university’s ElectroScience Laboratory, in a statement. “Now, for the first time, we’ve achieved the accuracy of printed metal circuit boards, so our new goal is to take advantage of the precision to incorporate receivers and other electronic components.” In the fabrication process, thread is substituted with fine silver metal wires. Previously, the researchers weaved a 600-filament count conductive polymer thread that was 0.5 mm in diameter, according to TechCrunch. The new threads are created using only seven threads, which are 0.1-mm in diameter. “Each filament is copper at the center, enameled with pure silver,” according to the university. In a test, the six-inch embroidered spiral antennas, which the researchers said may one day be able to broadband cellular and internet communication, successfully transmitted signals from one to five gigahertz. They estimate the material cost per antenna is around 30 cents, which is 24 times less expensive than the 2014 iteration. “A revolution is happening in the textile industry,” Volakis said. “We believe that functional textiles are an enabling technology for communications and sensing—and one day even medical applications like imaging and health monitoring.” The researchers published a paper on the technology in IEEE Antenna and Wireless Propagation Letters. Establish your company as a technology leader! For more than 50 years, the R&D 100 Awards have showcased new products of technological significance. You can join this exclusive community! Learn more.