Samsung researchers advance stretchable device technology

Suwon-si, South Korea – Researchers at the Samsung Advanced Institute of Technology (SAIT) have developed a technology to achieve a stretchable device with high elongation.

The SAIT researchers replaced the plastic material used in existing stretchable displays with an elastomer, to overcome the limitations of the devices, said a 4 June announcement. 

As part of the project, the team was able to integrate a stretchable organic LED (OLED) display and a photoplethysmography (PPG) sensor in a single device to measure and display the user’s heart rate in real-time, thus creating the ‘stretchable electronic skin’ form factor. 

More significantly, the team was able to modify the composition and structure of the elastomer and use existing semiconductor manufacturing processes to apply it to the substrates of stretchable OLED displays and optical blood flow sensors "for the first time in the industry", SAIT said. 

The sensor and display continued to operate normally and did not exhibit any performance degradation with elongation of up to 30%, according to the research.

“We applied an ‘island’ structure to alleviate the stress caused by elongation,” explained researcher Yeongjun Lee, co-first author of the paper. 

“More stress was induced in the area of the elastomer, which has a relatively low elasticity coefficient and is thus more likely to become deformed,” said Lee, adding that the move minimised the stress sustained by the OLED pixel area, which is more vulnerable to such pressure. 

The team then applied a stretchable electrode material (cracked metal) that resists deformation to the elastomer area, and this allowed the spaces and wiring electrodes between the pixels to stretch and shrink without the OLED pixels themselves becoming deformed.

To put their research to the test, the SAIT researchers attached stretchable PPG heart rate sensors and OLED display systems to the inner wrist of a patient near the radial artery. 

The test proved that wrist movement did not cause any property deterioration, with the solution remaining reliable as skin elongated. 

“This test also confirmed that the sensor and OLED display continued to work stably even after being stretched 1,000 times,” said the announcement. 

Furthermore, when measuring signals from a moving wrist, the sensor picked up a heartbeat signal that was 2.4 times stronger than the one picked up by a fixed silicon sensor.
 
“The strength of this technology is that it allows you to measure your biometric data for a longer period without having to remove the solution when you sleep or exercise,” explained principal researcher Youngjun Yun, corresponding author of the paper.

The technology, he added, can be expanded to use in wearable healthcare products for adults, children and infants, as well as patients with certain diseases.

According to SAIT, the research has proved the commercialisation potential of stretchable devices as the technology is capable of being integrated with existing semiconductor processes.