Ambient light enables 24-hour monitoring in wearable devices

Professor Kyeongha Kwon’s team at KAIST’s School of Electrical Engineering, in collaboration with Dr. Chanho Park’s lab at Northwestern University, announced the development of an adaptive wearable platform that optimizes energy use based on lighting conditions. 

To reduce battery load, the platform integrates three light energy technologies: 

• Photometric method: Dynamically adjusts LED brightness based on natural light. It dims the LED when ambient light is strong and brightens it under low light, reducing energy usage by up to 86.22 percent. 

• Photovoltaic method: Uses high-efficiency multijunction solar cells to harvest light indoors and outdoors. A smart power manager switches between 11 configurations to optimize performance. 

• Photoluminescent method: Incorporates strontium aluminate microparticles in the silicone encapsulation. These absorb and store light during the day and slowly release it in darkness, providing limited self-illumination after light exposure. 

These systems complement each other: the photometric and photovoltaic components operate in light, while the photoluminescent layer sustains functionality in darkness. 

The researchers tested the system with several medical sensors to demonstrate practical application: 

• A photoplethysmography sensor continuously tracks heart rate and blood oxygen levels, aiding in early cardiovascular diagnosis. 

• A blue light dosimeter measures blue light and supports personalized skin protection. 

• A sweat sensor with microfluidic channels analyzes sodium, glucose, and pH levels, offering real-time data on hydration and electrolyte balance. 

Data processing now occurs within the sensor itself, reducing wireless transmission needs from 400 bytes per second to just 4 bytes. 

To assess the platform’s reliability, tests were conducted under various lighting conditions: bright indoor lighting, low light, infrared light, and complete darkness. In all cases, the wearable showed accuracy comparable to commercial medical devices. Mouse model tests further confirmed reliable blood oxygen readings under hypoxic conditions. 

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

MEDICA-tradefair.com; Source: KAIST (Korea Advanced Institute of Science and Technology)