MIT: Introducing the latest in textiles: Soft hardware


MIT-Fiber-Diodes-01_0For the first time, the researchers from MIT and AFFOA have produced fibers with embedded electronics that are so flexible they can be woven into soft fabrics and made into wearable clothing.: Courtesy of the researchers

Researchers incorporate optoelectronic diodes into fibers and weave them into washable fabrics.

The latest development in textiles and fibers is a kind of soft hardware that you can wear: cloth that has electronic devices built right into it.

Researchers at MIT have now embedded high speed optoelectronic semiconductor devices, including light-emitting diodes (LEDs) and diode photodetectors, within fibers that were then woven at Inman Mills, in South Carolina, into soft, washable fabrics and made into communication systems. This marks the achievement of a long-sought goal of creating “smart” fabrics by incorporating semiconductor devices — the key ingredient of modern electronics — which until now was the missing piece for making fabrics with sophisticated functionality.

This discovery, the researchers  say, could unleash a new “Moore’s Law” for fibers — in other words, a rapid progression in which the capabilities of fibers would grow rapidly and exponentially over time, just as the capabilities of microchips have grown over decades.

The findings are described this week in the journal Nature in a paper by former MIT graduate student Michael Rein; his research advisor Yoel Fink, MIT professor of materials science and electrical engineering and CEO of AFFOA (Advanced Functional Fabrics of America); along with a team from MIT, AFFOA, Inman Mills, EPFL in Lausanne, Switzerland, and Lincoln Laboratory.

A spool of fine, soft fiber made using the new process shows the embedded LEDs turning on and off to demonstrate their functionality. The team has used similar fibers to transmit music to detector fibers, which work even when underwater. (Courtesy of the researchers)

Optical fibers have been traditionally produced by making a cylindrical object called a “preform,” which is essentially a scaled-up model of the fiber, then heating it. Softened material is then drawn or pulled downward under tension and the resulting fiber is collected on a spool.

The key breakthrough for producing  these new fibers was to add to the preform light-emitting semiconductor diodes the size of a grain of sand, and a pair of copper wires a fraction of a hair’s width. When heated in a furnace during the fiber-drawing process, the polymer preform partially liquified, forming a long fiber with the diodes lined up along its center and connected by the copper wires.

In this case, the solid components were two types of electrical diodes made using standard microchip technology: light-emitting diodes (LEDs) and photosensing diodes. “Both the devices and the wires maintain their dimensions while everything shrinks around them” in the drawing process, Rein says. The resulting fibers were then woven into fabrics, which were laundered 10 times to demonstrate their practicality as possible material for clothing.

“This approach adds a new insight into the process of making fibers,” says Rein, who was the paper’s lead author and developed the concept that led to the new process. “Instead of drawing the material all together in a liquid state, we mixed in devices in particulate form, together with thin metal wires.”

One of the advantages of incorporating function into the fiber material itself is that the resulting  fiber is inherently waterproof. To demonstrate this, the team placed some of the photodetecting fibers inside a fish tank. A lamp outside the aquarium transmitted music (appropriately, Handel’s “Water Music”) through the water to the fibers in the form of rapid optical signals. The fibers in the tank converted the light pulses — so rapid that the light appears steady to the naked eye — to electrical signals, which were then converted into music. The fibers survived in the water for weeks.

Though the principle sounds simple, making it work consistently, and making sure that the fibers could be manufactured reliably and in quantity, has been a long and difficult process. Staff at the Advanced Functional Fabric of America Institute, led by Jason Cox and Chia-Chun Chung, developed the pathways to increasing yield, throughput, and overall reliability, making these fibers ready for transitioning to industry. At the same time, Marty Ellis from Inman Mills developed techniques for weaving these fibers into fabrics using a conventional industrial manufacturing-scale loom.

“This paper describes a scalable path for incorporating semiconductor devices into fibers. We are anticipating the emergence of a ‘Moore’s law’ analog in fibers in the years ahead,” Fink says. “It is already allowing us to expand the fundamental capabilities of fabrics to encompass communications, lighting, physiological monitoring, and more. In the years ahead fabrics will deliver value-added services and will no longer just be selected for aesthetics and comfort.”

He says that the first commercial products incorporating this technology will be reaching the marketplace as early as next year — an extraordinarily short progression from laboratory research to commercialization. Such rapid lab-to-market development was a key part of the reason for creating an academic-industry-government collaborative such as AFFOA in the first place, he says. These initial applications will be specialized products involving communications and safety. “It’s going to be the first fabric communication system. We are right now in the process of transitioning the technology to domestic manufacturers and industry at an unprecendented speed and scale,” he says.

In addition to commercial applications, Fink says the U.S. Department of Defense — one of AFFOA’s major supporters — “is exploring applications of these ideas to our women and men in uniform.”

Beyond communications, the fibers could potentially have significant applications in the biomedical field, the researchers say. For example, devices using such fibers might be used to make a wristband that could measure pulse or blood oxygen levels, or be woven into a bandage to continuously monitor the healing  process.

The research was supported in part by the MIT Materials Research Science and Engineering Center (MRSEC) through the MRSEC Program of the National Science Foundation, by the U.S. Army Research Laboratory and the U.S. Army Research Office through the Institute for Soldier Nanotechnologies. This work was also supported by the Assistant Secretary of Defense for Research and Engineering.

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Long-Term Health Monitoring Possible through Breathable, Wearable Electronics on Our Skin


Nano Skin breathablewe
The diagram at top illustrates the structure of gold nanomesh conductors laminated onto the skin surface. The nanomesh, constructed from polyvinyl alcohol (PVA) nanofibers and a gold (Au) layer, adheres to the skin when sprayed with water, …more

A hypoallergenic electronic sensor can be worn on the skin continuously for a week without discomfort, and is so light and thin that users forget they even have it on, says a Japanese group of scientists. The elastic electrode constructed of breathable nanoscale meshes holds promise for the development of noninvasive e-skin devices that can monitor a person’s health continuously over a long period.

Wearable electronics that monitor heart rate and other vital health signals have made headway in recent years, with next-generation gadgets employing lightweight, highly elastic materials attached directly onto the skin for more sensitive, precise measurements. However, although the  and rubber sheets used in these devices adhere and conform well to the skin, their lack of breathability is deemed unsafe for long-term use: dermatological tests show the fine, stretchable materials prevent sweating and block airflow around the skin, causing irritation and inflammation, which ultimately could lead to lasting physiological and psychological effects.

“We learned that devices that can be worn for a week or longer for continuous monitoring were needed for practical use in medical and sports applications,” says Professor Takao Someya at the University of Tokyo’s Graduate School of Engineering whose research group had previously developed an on-skin patch that measured oxygen in blood.

In the current research, the group developed an electrode constructed from nanoscale meshes containing a water-soluble polymer, polyvinyl alcohol (PVA), and a gold layer—materials considered safe and biologically compatible with the body. The  can be applied by spraying a tiny amount of water, which dissolves the PVA nanofibers and allows it to stick easily to the skin—it conformed seamlessly to curvilinear surfaces of human skin, such as sweat pores and the ridges of an index finger’s fingerprint pattern.

Breathable, wearable electronics on skin for long-term health monitoring
An array of nanomesh conductors attached to a fingertip, top, and a scanning electron microscope (SEM) image of a nanomesh conductor on a skin replica, bottom. Credit: 2017 Someya Laboratory.

The researchers next conducted a skin patch test on 20 subjects and detected no inflammation on the participants’  after they had worn the device for a week. The group also evaluated the permeability, with water vapor, of the nanomesh conductor—along with those of other substrates like ultrathin plastic foil and a thin rubber sheet—and found that its porous mesh structure exhibited superior gas permeability compared to that of the other materials.

Furthermore, the scientists proved the device’s mechanical durability through repeated bending and stretching, exceeding 10,000 times, of a conductor attached on the forefinger; they also established its reliability as an electrode for electromyogram recordings when its readings of the electrical activity of muscles were comparable to those obtained through conventional gel electrodes.

Breathable, wearable electronics on skin for long-term health monitoring
The electric current from a flexible battery placed near the knuckle flows through the conductor and powers the LED just below the fingernail. Credit: 2017 Someya Laboratory.

“It will become possible to monitor patients’ vital signs without causing any stress or discomfort,” says Someya about the future implications of the team’s research. In addition to nursing care and medical applications, the new device promises to enable continuous, precise monitoring of athletes’ physiological signals and bodily motion without impeding their training or performance.

 Explore further: Novel e-skin may monitor health, vital signs

More information: Akihito Miyamoto et al, Inflammation-free, gas-permeable, lightweight, stretchable on-skin electronics with nanomeshes, Nature Nanotechnology (2017). DOI: 10.1038/nnano.2017.125

 

ASU: Stretchable Battery could Power Future Wearable Devices, Smart Clothes: Video


Israeli 0422 flexible-screen-811x497Using a twist on the art of origami paper folding, a research team at Arizona State University has created batteries that would be ideal for watch bands and connected clothing.

A team of researchers at Arizona State University has created a battery that can stretch up to 150 percent, opening the door for embedded power packs in smartwatches, clothes and other devices.

The approach is based on kirigami — a twist on origami, or paper folding — that turns a solid battery into several smaller ones with various folds and cuts. The result? A battery that isn’t a small brick, but instead can twist, bend and stretch while still providing full power.

That could be the “killer application” for such batteries although there’s an obvious potential application in smartwatch bands. Wearable devices don’t actually have to be devices.

I’ve already tested a shirt — or biometric smartwear to be more precise — that measures my real time heart rate and respiration, for example.

The conductive fibers to do so are woven in to the shirt but they need power to transmit the data over Bluetooth to a mobile app. Currently, that power is found with the Bluetooth radio in a blocky, plastic module. Adding in a stretchable battery would reduce much of the module’s bulk and also provide flexibility for the garment to stretch.

While our biggest battery challenge is still the amount of power capacity we can store in a given space, ASU’s effort shows that we can still make some tweaks that could radically change the form of a battery; even in smart clothes.