Ultrathin 'elastic skin' display developed for home health care

Japanese researchers have invented an ultrathin elastic display that can show the moving waveform of an electrocardiogram recorded by an on-skin electrode sensor that fits snugly on the skin. The integrated biomedical sensor system — called ‘skin electronics’ — can even transmit biometric data to the cloud.

Thanks to advances in semiconductor technology, wearable devices can now monitor health by first measuring vital signs or taking an electrocardiogram, and then transmitting the data wirelessly to a smartphone. The readings or electrocardiogram waveforms can either be displayed on the screen in real time, or sent to the cloud or a memory device.

The new skin electronics system aims to go a step further by enhancing information accessibility for people such as the elderly or the infirm, who tend to have difficulty operating and obtaining data from existing devices and interfaces. It aims to help ease the strain on home healthcare systems in ageing societies through continuous, non-invasive health monitoring and self-care at home.

Developed via a collaboration between The University of Tokyo and Japanese printing company Dai Nippon Printing (DNP), the skin display consists of a 16 x 24 array of micro LEDs and stretchable wiring mounted on a rubber sheet. The integrated system combines a flexible, deformable display with a lightweight sensor composed of a breathable nanomesh electrode and wireless communication module.

“Our skin display exhibits simple graphics with motion,” said Professor Takao Someya, leader of the research. “Because it is made from thin and soft materials, it can be deformed freely.”

The display is stretchable by as much as 45% of its original length, making it more resistant to the wear and tear of stretching than previous wearable displays. It is built on a novel structure that minimises the stress resulting from stretching on the juncture of hard materials, such as the micro LEDs, and soft materials, like the elastic wiring — a leading cause of damage for other models.

It is also said to be the first stretchable display to achieve good durability and stability in air, with the researchers finding that not a single pixel failed in the matrix-type display while attached snugly onto the skin and continuously subjected to the stretching and contracting motion of the body.

The nanomesh skin sensor, developed as part of an earlier study, can be worn on the skin continuously for a week without causing any inflammation. It had previously been found capable of measuring temperature, pressure and myoelectricity (the electrical properties of muscle), but this study marked the first time it successfully recorded an electrocardiogram and stored it in memory.

The researchers applied tried-and-true methods used in the mass production of electronics — specifically, screen printing the silver wiring and mounting the micro LEDs on the rubber sheet with a chip mounter and solder paste commonly used in manufacturing printed circuit boards. Applying these methods is expected to accelerate the commercialisation of the display and help keep down future production costs, with DNP looking to bring the integrated skin display to market within the next three years.

“The current ageing society requires user-friendly wearable sensors for monitoring patient vitals in order to reduce the burden on patients and family members providing nursing care,” said Professor Someya. “Our system could serve as one of the long-awaited solutions to fulfil this need, which will ultimately lead to improving the quality of life for many.”

Image caption: The soft, flexible skin display is about 1 mm thick. Image credit: 2018 Takao Someya Research Group.