Japanese Researchers Develop Ultraflexible ‘E-Skin’
Professor Takao Someya’s research group at the University of Tokyo’s Graduate School of Engineering has developed an ultraflexible ‘e-skin’ film and demonstrated its use by creating an organic light-emitting diode display.
System outline of a blood oxygen level monitor: red and green PLEDs are directed to shine into the finger; reflected light from inside the finger is caught by an ultraflexible organic photodetector; this reflected light provides a measure of blood oxygen and pulse rate; the output of the sensor can be shown on a PLED display. Image credit: Tomoyuki Yokota et al. / Someya Laboratory, University of Tokyo.
Integrating electronic devices with the human body to enhance or restore body function for biomedical applications is the goal of researchers around the world.
In particular, wearable electronics need to be thin and flexible to minimize impact where they attach to the body.
However, most devices developed so far have required millimeter-scale thickness glass or plastic substrates with limited flexibility, while micrometer-scale thin flexible organic devices have not been stable enough to survive in air.
Prof. Someya and co-authors have developed a high-quality protective film less than 2 μm thick that enables the production of ultrathin, ultraflexible, high performance wearable electronic displays and other devices.
The scientists developed the protective film by alternating layers of inorganic (silicon oxynitrite) and organic (parylene) material.
They were able to attach transparent indium tin oxide electrodes to an ultrathin substrate without damaging it, making the ‘e-skin’ display possible.
Using the new protective layer and indium tin oxide electrodes, the team created polymer light-emitting diodes (PLEDs) and organic photodetectors (OPDs).
These were thin enough to be attached to the skin and flexible enough to distort and crumple in response to body movement.
“The total thickness of the devices, including the substrate and encapsulation layer, is only 3 μm, which is one order of magnitude thinner than the epidermal layer of human skin,” Prof. Someya and his colleagues said.
“By integrating green and red PLEDs with OPDs, we fabricate an ultraflexible reflective pulse oximeter. The device unobtrusively measures the oxygen concentration of blood when laminated on a finger.”
“On-skin seven-segment digital displays and color indicators can visualize data directly on the body.”
The results were published online April 15, 2016 in the journal Science Advances .