An ultra-thin, flexible, organic light-emitting diode (OLED) display has been created using a protective layer developed by University of Tokyo researchers.
The technology could see electronic devices integrated into dressings that attach to the human body to enhance or restore body function for biomedical applications.
Electronic skin (e-skin) displays have been developed with the new layer that show blood oxygen levels and tracking of the wearers heart rate, among other applications.
Wearable electronics need to be thin and flexible to minimise their impact on the part of the body they attach to.
Yet similar devices developed in the past have required millimetre-scale thickness glass or plastic substrates with limited flexibility, while micrometre-scale thin flexible organic devices have not been stable enough to survive in air.
The new protective film measures less than two micrometres thick and was developed by alternating layers of inorganic (Silicon Oxynitrite) and organic (Parylene) material.
The protective film prevented passage of oxygen and water vapour in the air, extending device lifetimes from the few hours seen in earlier technologies to several days.
The research group also attached transparent indium tin oxide (ITO) electrodes to the ultra-thin material without damaging it, making the e-skin display possible.
Using the new protective layer and ITO electrodes, light-emitting diodes (PLEDs) and organic photodetectors (OPDs) could be placed directly onto the skin.
These were thin and flexible enough to allow them to distort and crumple in response to body movement.
The PLEDs were just three micrometres thick and over six times more efficient than previously reported ultra-thin PLEDs due to reduced heat generation and power consumption.
This makes them particularly suitable for direct attachment to the body for medical applications like displays for blood oxygen concentration or pulse rate. The research group also combined red and green PLEDs with a photodetector to demonstrate a blood oxygen sensor.
"The advent of mobile phones has changed the way we communicate. While these communication tools are getting smaller and smaller, they are still discrete devices that we have to carry with us," said Professor Takao Someya who worked on the project.
"What would the world be like if we had displays that could adhere to our bodies and even show our emotions or level of stress or unease? In addition to not having to carry a device with us at all times, they might enhance the way we interact with those around us or add a whole new dimension to how we communicate."
Last year, scientists from Saarland University in Germany demonstrated flexible sensors that could allow people to interact with their mobile phones by touching their skin.