Over the weekend, Samsung teased its latest stretchable display technology for heart rate monitoring devices.

In a press statement, the Korean electronics giant said its researchers at the Samsung Advanced Institute of Technology (SAIT) were able to integrate a stretchable organic LED (OLED) display and a photoplethysmography (PPG) sensor in a single device to measure and display a user's heart rate in real-time.

FINDINGS

The researchers were able to test a prototype of the skin patch by attaching it to a user's inner wrist near the radial artery where a pulse is usually checked.

Based on their findings published in Science Advances, the wrist movement did not cause any performance degradation with the solution operating normally even if elongated up to 30%.

It was also found that the sensor and OLED display "continued to work stably" even after being stretched a thousand times. Moreover, the sensor has picked up a heartbeat signal "2.4 times stronger" than what would be picked up by a fixed silicon sensor.

Overcoming performance deterioration in existing stretchable devices, SAIT researchers opted for elastomer, a material with rubber-like properties, instead of the usual plastic material.

But since elastomeric material is vulnerable to heat, the team also strengthened the display's thermal and chemical resistance. "We applied an ‘island’ structure to alleviate the stress caused by elongation," said Yeongjun Lee, the study's co-first author said.

"We 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."

WHY IT MATTERS

Samsung said the stretchable device was designed to allow continuous heartbeat measurements with a high degree of sensitivity.

"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, since the patch feels like part of your skin," Youngjun Yun, principal researcher and corresponding author of the study, explained.

Yun said the technology can be applied in wearable health products for adults, children, and infants, as well as patients with certain diseases.

Moreover, the elastomeric material in the device was also made chemical and heat resistant, "thereby making commercialization of stretchable devices with high resolution and large screens more likely in the future".

The researchers are eyeing to incorporate the stretchable sensors and freeform displays in devices that monitor peripheral oxygen saturation, electromyogram readings and blood pressure.

MARKET SNAPSHOT

MC10 is one of the most recognisable names in the wearable health technology space. In 2014, its co-founder John Rogers and his fellow researcher Yonggang Huang publicised their research on an off-the-shelf chip for peel-and-stick health monitoring patches.

In the same year, a competing research team at North Carolina State University led by Dr Yong Zhu came up with wearable sensors made up of silver nanowires, which can measure strain, pressure, human touch and bioelectronic signals.

Two years later, MC10 commercially rolled out a research-ready version of its BioStamp, a thin patch that measures heart electrical activity, hydration, body temperature and UV exposure. It has a flexible sensor that can be worn in various areas of the body.

In 2018, the Cambridge, Massachusetts-based sensor maker received the US FDA's approval for its BioStamp nPoint platform, a more advanced version of the non-FDA cleared BioStamp Research Connect. It differs from the latter as it can also monitor derived data, including heart rate variation, posture classification and other sleep-related metrics.

The following year, tech giant Apple's patent application for a stretchable health-tracking band was published. The stretchable fabric band was envisioned to include circuitry sensors to measure blood pressure, respiration rate and ECG signals.

ON THE RECORD

"Our research is still in the early stages, but our goal is to realize and commercialise stretchable devices by increasing system resolution, stretchability and measurement accuracy to a level that makes mass production possible," said Jong Won Chung, principal researcher and co-first author of the study.