Non-invasive ‘e-Skin’ monitors the body’s vital signs

‘e-Skin’ monitors
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Researchers from the University of Tokyo, publishing in the journal ‘Science Advances’ report that their ‘e-skin,’ laminated on to the actual skin of a wearer, was used to accurately monitor the levels of oxygen in the blood of volunteers during testing.

The ultra-thin, flexible skin contains polymeric light-emitting diodes (PLEDs) which light up in red, green or blue depending on how oxygen levels measure up. The skin can also be customised to display different data on various parts of the body. The researchers are now working on ways to display specific numbers and letters onto the skin.

More than just surgery

Moreover, the invention could not just be used to measure and monitor patient health during surgery but could also be implemented in a wide range of bioengineering and next-generation medical technologies. Thin-film monitoring could be used in connection with advanced prosthetics or implemented with sensors for monitoring a range of health conditions.

‘Our e-skin can be directly laminated on the surface of the skin, allowing us to electronically functionalise human skin,’ said Takao Someya, a professor in the Department of Electrical and Electronic Engineering at the University of Tokyo. ‘We think that functionalising the skin may replace the smartphone in the future. When you carry an iPhone, it is a bulky device. But if you functionalise your own skin, you don’t need to carry anything, and it’s easy to receive information anywhere, anytime.’

Previous organic electronic displays have been built using glass or plastic base materials, or substrates, but their flexibility was limited by their thickness. Other, thinner versions have been manufactured, however these materials have not been stable enough to endure exposure to air for more than a few hours.

Extending device lifetime

Prof. Someya’s team was able to extend the device’s lifetime to several days by creating a protective film, called a passivation layer, which consists of alternating layers of inorganic silicon oxynitride and organic parylene. The film shields the device from damaging oxygen and water vapour but is so thin that the entire device is just three micrometres thick and highly flexible. For comparison, a strand of hair is about 40 micrometres thick.

Substrates this thin can be easily deformed by the high-energy processes needed to produce the ultrathin, transparent electrodes that connect the components, Prof. Someya also commented. As such, the group’s second innovation was to optimise these processes to reduce the required energy to a level that did not damage the ultrathin materials.

What is so exciting about this invention is that it proves that wearable technology need not be either cumbersome or invasive, both of which will be essential factors for convincing future consumers to use such devices. Additionally all of the devices developed by the research group were flexible enough to distort and crumple in response to body movement, without losing their functionality.

Wearable electronics have long been seen as a future growth area and many companies have already attempted to pioneer this market (Google’s Glass being a prominent example). Arguably much commercial interest in wearable technology is now firmly focused on the development of wearable medical applications in the same vein as the Japanese e-skin, such as novel contact lenses that monitor glucose levels.

Suffice to say, innovative products such as this ultrathin e-skin are pointing towards a future where the lines between man and machine will indeed become ever-more blurred.