Miniaturizing and reducing the weight of wearable medical devices remains a critical hurdle in enabling continuous health monitoring, especially for vital signs like heart rate, blood oxygen saturation, and sweat composition. A key limitation is the high-power consumption of optical sensors, which require constant LED operation and wireless data transmission, often necessitating bulky batteries. These constraints make current wearable technologies cumbersome and unsuited for long-term, uninterrupted use. Now, researchers have developed a wearable solution that reduces battery burden by harvesting ambient light and optimizing power management based on environmental conditions, enabling 24-hour continuous operation.

This adaptive wireless wearable platform, developed by the Korea Advanced Institute of Science and Technology (KAIST, Daejeon, South Korea), in collaboration with Northwestern University (Evanston, IL, USA), integrates three complementary technologies to harvest and manage energy from ambient light sources. The first, the Photometric Method, dynamically adjusts LED brightness based on surrounding light, dimming in bright conditions and brightening in dim settings, which led to power savings of up to 86.22% in well-lit environments. The second, the Photovoltaic Method, uses high-efficiency multijunction solar cells to generate electricity under both indoor and outdoor lighting. It includes an adaptive system that switches among 11 power configurations for optimal energy use. The third, the Photoluminescent Method, incorporates strontium aluminate microparticles into the sensor's encapsulation. These particles absorb light during the day and emit it in darkness, providing backup illumination for measurements even when no light is present. Together, these three methods operate in synergy to maintain continuous device functionality across varied lighting conditions. The platform also includes in-sensor data computing, which reduces wireless communication needs by compressing data from 400B/s to just 4B/s.

To validate the platform, researchers tested it across four lighting conditions—bright indoor, dim lighting, infrared, and total darkness—using healthy adult participants. The findings, published in Nature Communications, show that the wearable device demonstrated measurement accuracy on par with commercial medical equipment. In mouse model tests, it accurately measured blood oxygen saturation even under hypoxic conditions. The system supported various sensor applications, including a photoplethysmography sensor for heart rate and oxygen saturation, a blue light dosimeter for skin protection, and a sweat sensor for monitoring salt, glucose, and pH. Looking ahead, the team anticipates broader adoption of this energy-autonomous wearable technology for preventive healthcare, reduced healthcare costs, and enhanced competitiveness in the wearable medical device market.

“This technology will enable 24-hour continuous health monitoring, shifting the medical paradigm from treatment-centered to prevention-centered,” said Professor Kyeongha Kwon, lead researcher of the study. “Cost savings through early diagnosis as well as strengthened technological competitiveness in the next-generation wearable healthcare market are anticipated.”

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