Ultrasonic Sensor Enables Cuffless and Non-Invasive Blood Pressure Measurement

Optical cuffless methods exist, but their accuracy is often compromised by skin color, motion, lighting conditions, and limited ability to assess deeper blood vessels. These limitations have slowed the adoption of continuous, wearable blood pressure monitoring in daily life. Researchers have now developed a noninvasive, cuff-free approach that directly measures real-time vascular diameter changes beneath the skin using ultrasound to calculate blood pressure.

Researchers at the Korea Institute of Machinery and Materials (KIMM, Daejeon, South Korea), in collaboration with the Korea Institute of Science and Technology (KIST, Seoul, South Korea), have developed a wearable ultrasonic sensor that could conform to human skin while maintaining high signal quality and measurement accuracy. The device is built using PMN-PT single-crystal piezoelectric composites integrated onto a flexible substrate through a dual-side low-temperature tin–bismuth soldering process. This approach prevents thermal depolarization and preserves the exceptional electromechanical properties of the material.

The sensor is designed as a 5×4 ultrasonic transducer array mounted on a flexible polyimide substrate and encapsulated with Parylene-C. With a total thickness under 0.5 mm and a weight below 1 gram, it adheres securely to the skin for long-term wear without discomfort. During operation, the device emits ultrasonic waves into the body, detects echoes reflected from blood vessel walls, and measures dynamic changes in vascular diameter. These diameter variations are then used to calculate systolic and diastolic blood pressure in real time.

The system was validated using an artificial skin vascular phantom to simulate human blood vessels. Measurements showed systolic and diastolic blood pressure errors of ±4 mmHg and ±2.3 mmHg, respectively, meeting the AAMI clinical accuracy standard. The findings demonstrate that ultrasound-based sensing can outperform existing optical cuffless methods by directly measuring deep blood vessels with a high signal-to-noise ratio and reliability. The results highlight the platform’s accuracy, flexibility, and suitability for continuous monitoring.

This cuff-free ultrasonic technology could become a core component of next-generation wearable healthcare devices and smart medical monitoring systems. Its ability to continuously track blood pressure noninvasively makes it particularly relevant for long-term cardiovascular disease management and early risk detection. The researchers plan to further integrate the sensor with AI-based blood pressure analysis, enabling personalized cardiovascular monitoring and predictive healthcare applications.

“This technology is the first to demonstrate continuous, cuff-free blood pressure monitoring using a skin-attachable ultrasonic sensor,” said Dr. Shin Hur of KIMM. “Combined with AI-based blood pressure analysis, it will evolve into a core platform for personalized cardiovascular disease prediction and smart healthcare.”

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