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13th October 2014

A patch that tells you when your heart’s in trouble

A new wearable medical device that uses up to 3,600 liquid crystals can quickly let you know if you’re having heart trouble—or if it’s simply time to slather on some moisturizer.

The small device, approximately five centimeters square, can be placed directly on the skin for around-the-clock health monitoring. The wireless technology uses thousands of tiny liquid crystals on a flexible substrate to sense heat. When the device turns color, the wearer knows something is awry.

“Our device is mechanically invisible—it is ultrathin and comfortable—much like skin itself,” says Yonggang Huang, professor of civil and environmental engineering and mechanical engineering at Northwestern University.

Huang and colleagues tested the device on people’s wrists.

“One can imagine cosmetics companies being interested in the ability to measure skin’s dryness in a portable and non-intrusive way,” Huang says. “This is the first device of its kind.”

The technology and its relevance to basic medicine have been demonstrated in the study, but additional testing is needed before it can be put to use. Details are reported online in the journal Nature Communications.

“The device is very practical,” says Yihui Zhang, co-first author and research assistant professor of civil and environmental engineering. “When your skin is stretched, compressed, or twisted, the device stretches, compresses or twists right along with it.”

3,600 Temperature Points

The technology uses the transient temperature change at the skin’s surface to determine blood flow rate, which is of direct relevance to cardiovascular health and skin hydration levels. (When skin is dehydrated, the thermal conductivity property changes.)

The device is an array of up to 3,600 liquid crystals, each half a millimeter square, laid out on a thin, soft, and stretchable substrate.

When a crystal senses temperature, it changes color and the dense array provides a snapshot of how the temperature is distributed across the area of the device. An algorithm translates the temperature data into an accurate health report, all in less than 30 seconds.

“These results provide the first examples of ‘epidermal’ photonic sensors,” says John A. Rogers, the paper’s corresponding author and professor of materials science and engineering at the University of Illinois. “This technology significantly expands the range of functionality in skin-mounted devices beyond that possible with electronics alone.”

With its 3,600 liquid crystals, the photonic device has 3,600 temperature points, providing sub-millimeter spatial resolution that is comparable to the infrared technology currently used in hospitals.

The infrared technology, however, is expensive and limited to clinical and laboratory settings, while the new device offers low cost and portability.

The device also has a wireless heating system that can be powered by electromagnetic waves present in the air. The heating system is used to determine the thermal properties of the skin.

Source: Northwestern University

Header Photo Credit: John A. Rogers/University of Illinois

This article originally appeared on Futurity on 26 September.