Researchers at the University of California, Berkeley, and collaborating institutions have developed a minimally invasive implantable ultrasound device capable of continuously monitoring blood pressure. The study, published in Microsystems & Nanoengineering on November 6, 2025, demonstrates a subcutaneous piezoelectric micromachined ultrasonic transducers (PMUTs) array that measures arterial diameter changes to derive precise blood pressure values.
Hypertension remains a leading cause of heart disease and stroke worldwide. Traditional cuff-based measurements are unsuitable for continuous monitoring, while wearable sensors often suffer from motion interference and misalignment. The implantable PMUT system addresses these limitations by providing stable, long-term monitoring without the need for gels or frequent recalibration.
The device consists of a 5 × 5 mm² array with 37 × 45 PMUTs, each featuring a 29-µm diaphragm operating at approximately 6.5 MHz. The dual-electrode bimorph design enhances acoustic output, and the array is fabricated using CMOS-compatible processes, ensuring high structural uniformity. Blood pressure is derived by measuring the time-of-flight between ultrasound echoes from the arterial walls, which correlates with vessel diameter and pressure.
During in vivo testing in an adult sheep, the implanted device captured detailed pressure waveforms, including the dicrotic notch, and matched gold-standard arterial line measurements within −1.2 ± 2.1 mmHg (systolic) and −2.9 ± 1.4 mmHg (diastolic). This performance demonstrates clinical reliability and stability against motion and tissue growth.
“The study shows that ultrasound-based implants can achieve the stability and precision required for continuous blood pressure monitoring without the drawbacks of cuffs or fragile wearables,” said the corresponding author. “By capturing arterial diameter changes directly through subcutaneous sensing, the device avoids issues like gel dependence, environmental noise, and misalignment.”
The implantable PMUT system offers a promising alternative for patients requiring continuous, unobtrusive blood pressure measurement. Its stability makes it suitable for long-term hypertension management and integration into digital health platforms. Future advancements, such as beamforming and data-driven analytics, could further enhance its clinical utility. The research was supported by BSAC (Berkeley Sensor and Actuator Center).
