Electronic skin: from flexibility to a sense of touch

Material scientists believe that it will not be the first to be pulled into the fight against COVID-19. But it happened to John Rogers.

He leads a team at Northwestern University in Evanston, Illinois, which develops soft, flexible, skin-like materials with health-monitoring applications.

A device, designed to sit hollow at the base of the throat, is a wireless, Bluetooth-connected piece of polymer and circuitry that provides real-time monitoring of talking, breathing, heart rate, and other vital signals , Which can be used in individuals who have had a stroke and need speech therapy 1.

Physicians wanted to know if the device could be adapted to the symptoms of coronavirus SARS-CoV-2. The short answer was ‘yes’.

Some 400 devices are now being used in Chicago, Illinois to help front-line health workers understand early signs of COVID-19, as well as to monitor disease in patients. His team advances the design to assess how cough rates change in people with COVID-19.

“Many of us, designated as essential workers because of our COVID device work, have been in the lab on a daily basis during this period,” Rogers says. “I haven’t missed a single day.” His team members also wear equipment in the lab to monitor themselves for the onset of symptoms. “So far, nothing,” he says.

Rogers is one of the most prolific researchers of wearable skin-inspired electronics worldwide. For example, this into e-skin ‘technology has already made its way into volunteers and clinics globally, which helps to monitor vital signs in hydration in premature infants and athletes.

Other e-skins are giving the robot a light, human touch. But whether they are for people or robots, such devices represent a significant chemical and engineering challenge: electronic components are usually brittle and inflexible, and human skin is a malleable but tough canvas.

Flexible Screen, Flexible Circuit

E-skin devices have their roots in components found in e-book readers and curved televisions, developed by scientists working on flexible, carbon-based molecules or polymers that conduct electricity.

“The crowd of organic electronics was working on organic light-emitting diodes for display and lighting, display backplanes and transistors for large-area electronics, and solar-,” says George Malliras, who studied bioelectronics at the University of Cambridge.

Photovoltaic cell for energy storage. , Britain. “At some point, all these applications will benefit from flexible form factors.” That flexibility says “wearable electronics proved to be very useful when it came to the foreground”.

One of the earliest successes of this field came in 2004. Takao Kooya, an electrical engineer at the University of Tokyo, and his team reported that they had developed a flexible 8 cm × 8 cm patch of robotic skin constructed from high-performance layers, pressure-sensing polyamide plastic, an organic semiconductor called pentacene and gold.

And are called layers of copper electrodes. With no silicon in sight, a 32 × 32 array of small pressure sensors was placed in the square. And this allowed the current to flow seamlessly, even when it was wrapped around a 4-millimeter thick cylindrical strip, such as a viable circuit board 2.

“Our team took an active matrix, which evolved into a drive circuit for a flexible display,” says Koya. And it gave robots something they never had: a sense of touch from the ability to respond to pressure.

But the skin should be more than flexible, one realized; It should also stretch and conform, and be able to respond to light touch. In 2005, his team cracked that problem by spinning relatively rigid polyimide polymers into strands and then into a net.

Under tension, the strands are twisted, allowing researchers to draw traps on the surface of the egg. The drawn mesh was able to feel the pressure change applied to the egg by contact with the rubber block. Adding organic semiconductor diodes to the purge means it can also measure temperature 3.

At Northwestern, Rogers took a different approach to the same challenge. He and his team often focus on creating ultrathin structures from nanometer-scale, tough, inorganic materials.

In 2006, researchers worked in a way to engineer submicrometry ribbons of single-crystal silicon and bind them to a sheet of rubber polydimethylsiloxane (PDMS) under stress. When they released tension, the silicon deformed into waves, which could level (but not break) as material deformation 4. “It’s a type of hybrid organic-inorganic approach,” says Rogers.

Wear it and forget it

As Maliarus sees it, wearable devices present two types of challenge: chemistry problems in search of an engineer, and engineering problems in need of a chemist.

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