Researchers from the University of California, Berkeley, and collaborating institutions have developed a subcutaneously implanted ultrasonic device capable of continuous, accurate blood pressure monitoring, as demonstrated in a study involving an ambulatory sheep. The findings, published in Microsystems & Nanoengineering on November 6, 2025, address critical limitations of existing monitoring methods and could significantly impact the management of hypertension, a leading global cause of heart disease and stroke.
Conventional blood pressure cuffs disrupt daily activity and are unsuitable for continuous tracking, while wearable alternatives like photoplethysmography (PPG) and ultrasound patches often struggle with shallow penetration, gel dependence, and sensitivity to motion or misalignment. The new implantable system, detailed in the paper (DOI: 10.1038/s41378-025-01019-w), uses a 5 × 5 mm² array of piezoelectric micromachined ultrasonic transducers (PMUTs) placed under the skin to measure real-time changes in arterial diameter, which correlate directly with blood pressure.
The device's dense 37 × 45 PMUT array, fabricated using CMOS-compatible processes, operates at about 6.5 MHz, enabling high-resolution echo penetration through tissue. By calculating the time-of-flight between ultrasound echoes from arterial walls, it reconstructs pressure waveforms. Bench-top experiments confirmed the linear relationship between diameter and pressure, and simulations highlighted that wearable systems can lose up to 60% signal strength with just 1 mm of misalignment—a problem the implanted design avoids by maintaining stable coupling.
In vivo testing involved implanting the system above the femoral artery of an adult sheep. The device successfully captured detailed pressure waveforms, including features like the dicrotic notch, and matched gold-standard arterial line measurements within −1.2 ± 2.1 mmHg for systolic and −2.9 ± 1.4 mmHg for diastolic pressures. This level of accuracy demonstrates the potential for clinical reliability with minimal calibration error, offering a solution that bypasses issues such as gel dependence and environmental noise.
The implications of this technology are substantial for cardiovascular care. Hypertension management currently relies on periodic measurements that may miss critical fluctuations, but this implant could provide continuous, high-fidelity data, enabling earlier detection of abnormalities and more personalized treatment strategies. Its stability against tissue growth and motion makes it suitable for long-term use, potentially integrating into digital health platforms for real-time monitoring. Future advancements, like beamforming to mitigate positional shifts, could further enhance its utility, supporting preventive care by delivering richer cardiovascular insights in everyday environments.
