Wearable electronics bring computers in your clothes

Researchers from the Ohio State University who are working to create wearable electronics have announced a major achievement. According to them, they are able to embroider circuits into fabric with 0.1 mm precision to incorporate 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 smartphone 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.

Figure 1: Researchers at The Ohio State University are developing embroidered antennas and circuits with 0.1mm precision, the perfect size to integrate electronic components such as sensors and computer memory devices into clothing. Photo by Jo McCulty, courtesy of The Ohio State University

"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 wearable electronics 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 results in the journal IEEE Antennas and Wireless Propagation

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.

Figure 2: Kiourti: The shape of the embroidery determines the frequency of operation of the antenna or circuit. (Photo by Jo McCulty, courtesy of the Ohio State University)

"We started with a technology that is very well known, machine embroidery, and we asked, how can we functionalise 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, which 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.

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