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TechWaTch
Computing Threads and Sewing Circuits
By Mike Skinner I
n what appears to be a milestone for the wearable electronics mar- ket, researchers at the Ohio State
University (OSU) have developed a process of embroidering circuits into clothing with 0.1 mm (0.004 in.) pre- cision. This level of accuracy now makes wearable circuitry, clothes that gather, store or transmit digital information, a reality. Soon, we may see applications
of the technology in shirts that act as antennas for smartphones or tablets, workout clothes that monitor athlet- ic performance, smart bandages that keep track of how wounds are heal- ing, or even flexible fabric caps that sense brain activity.
Thinking Caps John Volakis, director of the
ElectroScience Laboratory at OSU, and research scientist Asimina Kiourti are investigating ways to use the technology to make brain im-
plants more comfortable. With con- ductive thread sewn into a cap, the need for external wiring on a pa- tient’s body could be effectively elim- inated. This sort of application can lead to better treatments for condi- tions from epilepsy to addiction. Brain-computer interfaces, like
those that facilitate deep-brain stim- ulation, are now widely used for pa- tients with Parkinson’s disease or those with clinical depression — con- ditions that were previously thought incurable. A comfortable, conductive cap could communicate with medical equipment and provide information about activity in the brain. “A revolution is happening in
the textile industry,” says Volakis. “We believe that functional textiles are an enabling technology for com- munications and sensing — and one day even for medical applications like imaging and health monitoring.” At this point, the applications of
wearable electronics to augment body-machine interfaces are limited only by the imagination. For military, aerospace and de-
fense, the ability to monitor a soldier, pilot or astronaut’s vital signs while they perform critical tasks in life- threatening environments, and from great distances, is as simple as adding a thin layer of clothing under their suits.
For industry, monitoring
the status of workers in dan- gerous conditions, such as ex- posure to radiation or toxic chemicals, could be accom- plished by providing them with a jacket that both pro- tects them physically, and communicates digitally with safety programs. As a part of civilian life,
material cost of one antenna at around 30 cents. According to the team, that is 24 times cheaper than when they first created similar an- tennas in 2014. Part of the savings comes from using less thread per layer of embroi-
June, 2016
wearable circuitry would al- low for any number of luxuries. Imagine clothes that measure your waistline, for example, or shoes de- signed to check your weight and cor- rect your posture. In this digital era, the cloud is the limit.
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Shape Determines Function Consisting of over half a dozen
interlocking geometric shapes, each slightly bigger than a fingernail, one broadband antenna is formed by an intricately embroidered circle a few inches across. Each part of the shape transmits energy at a different fre- quency to cover a broad spectrum when working together. “Shape determines function,”
says Kiourti. “And, you never really know what shape you will need from one application to the next. We want- ed to have a technology that could embroider any shape for any applica- tion.”
An initial goal of the project was
to increase the precision of the em- broidering process as much as possi- ble, which necessitated the use of fine silver wire. A problem, however, is that fine wire does not provide as much surface conductivity as thicker wires. Working the fine thread into varying shapes and densities solves that problem and boosts the surface conductivity of the antenna or sensor performance. The threads have a 0.1 mm
(0.001 in.) diameter, and are made with only seven filaments. Each fila- ment has a copper center, and is enameled with pure silver.
Worth Its Weight in Silver A spool of wire costs 3 cents per
foot, and Kiourti estimates that a single broadband antenna requires about 10 feet of thread. This puts the
Embroidered antennas and circuits allow computer memory devices to be sewn into clothing. (Photo by Jo McCulty)
dery. Previously, the researchers had to stack thicker thread in multiple layers to make the antenna carry a strong enough electrical signal. Over time, they have refined their tech- nique enough to create high-preci- sion antennas in only one layer of fin- er thread. The process only takes about 15 minutes to create one an- tenna. Prototypes that the team have
come up with include a spiral-like shape that can be sewn into clothing to improve cell signal reception. An- other prototype, part of a study done for a tire manufacturer, is a stretch- able antenna with an RFID chip em- bedded in the rubber. Another circuit resembles the university’s “O” logo, which combines conductive and non- conductive scarlet and gray threads to demonstrate, according to Kiourti, that e-textiles can be both decorative and functional. Easy on the eyes, the embroi-
dered antennas and circuits are sur- prisingly functional. Tests have shown that an embroidered antenna measuring approximately 6 in. (152.4 mm) across transmitted sig- nals at frequencies of 1 to 5 GHz with near-perfect efficiency. With a current emphasis in
technology on the Internet of Things, this development in wearable elec- tronics is the next step toward a deeply interconnected daily life. Everyday clothes can boost cell re- ception, or communicate with smart devices for human-machine interface systems and monitoring. Until this next phase of science-fiction becomes reality, Volakis is working on a shop- ping list for the project’s next phase. “We want a bigger sewing machine,” he says. Source:
www.osu.edu r
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