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Science: Monitoring Vital Signs through Stretchable Electronic "Skin"
An ultra-thin electronic device attaches to the skin like a temporary tattoo and measures heart rate and other vital signs without the bulky electrodes used in current hospital monitoring, reports a new study in the 11 August issue of the journal Science.
The device could also potentially be used as an electronic bandage to speed up healing in wounds, burns, and other skin conditions, and it could even provide touch sense to prosthetic devices such as artificial legs or arms.
The complicated wiring involved in current hospital monitoring can be inconvenient and distressing for both patients and doctors. For example, a patient with heart disease is usually required to wear a bulky monitor for a month or more in order to capture abnormal but rare cardiac events.
The current best electrodes for these monitors are gel-coated adhesive pads. Many people, particularly those who have sensitive skins, will develop a rash from the adhesive. The electronic skin designed by John Rogers at the University of Illinois at Urbana-Champaign and colleagues sits on a layer of rubbery polyester engineered to have mechanical properties well matched to those of natural skin.
An epidermal electronic system, mounted on a commercial temporary transfer tattoo, shows extreme flexibility and deformation after being attached to the skin.
[Video courtesy of John A. Rogers]
“Our goal was to develop an electronic technology that could integrate with the skin in a way that is mechanically and physiologically invisible to the user,” Rogers said. “It's a technology that blurs the distinction between electronics and biology.”
Applied like a temporary tattoo, the device sticks to the skin by sheer attraction. Weak forces called van der Waals forces that exist between molecules of the same substance hold the device in place but do not interfere with normal skin motion. The device can bend, wrinkle, and stretch without being damaged.
The middle layer of the device consists of the metal, semiconductor, and insulator components needed for sensors, electronics, power supply, and light-emitting components. The design squeezes all of the necessary components in an ultra-thin layer about the thickness of a human hair.
Epidermal electronic systems integrate to the surface of the skin in a way that is mechanically invisible to the user, offering a range of healthcare and non-healthcare related functions.
[Image courtesy of John A. Rogers]
“There are a couple of large steps in manufacturing that are unique,” Rogers said in a 10 August Webcast discussing the research, “but most of it relies on established tools that are embedded in silicon IT factories.”
The researchers tested the electronic skin on participants and showed that the device works for up to 24 hours or more on the arm, neck, forehead, cheek, and chin, and that it does not irritate the skin.
The team also used the device to take measurements of the electrical activity produced by the leg muscles and heart of participants, and found that the device's signals matched signals taken simultaneously with the conventional setup of bulk electrodes, conductive gel, and tape.
The results suggest that electronic skins could one day replace conventional hospital monitoring techniques, and the researchers are exploring commercial partnerships to develop the technology.
“Our ultimate goal is to generate commercial products that can be a broad benefit to society,” Rogers said. “We will judge success by the extent to which this technology makes it into the wider world.”
11 August 2011