Researchers from the University of California, Berkeley, and collaborating institutions have developed a minimally invasive, implantable ultrasound device capable of providing continuous, clinically reliable blood pressure monitoring. The technology, detailed in a paper published in Microsystems & Nanoengineering (DOI: 10.1038/s41378-025-01019-w), addresses critical limitations of conventional monitoring methods and could significantly impact the management of hypertension, a leading global cause of heart disease and stroke.
Traditional cuff-based blood pressure measurements disrupt daily activity and are unsuitable for continuous tracking. Alternatives like photoplethysmography (PPG) and wearable ultrasound patches often struggle with shallow penetration depth, gel dependence, and sensitivity to motion or misalignment. The new system, built on a 5 × 5 mm² array of piezoelectric micromachined ultrasonic transducers (PMUTs), is implanted subcutaneously to continuously measure arterial diameter changes, from which precise blood pressure waveforms are derived. This approach avoids the intrusive placement inside arteries required by some implantable sensors and mitigates issues of foreign-body reactions.
The device's dense 37 × 45 PMUT array, fabricated using CMOS-compatible processes, operates at approximately 6.5 MHz, enabling high axial resolution and strong echo penetration through tissue. A dual-electrode bimorph design enhances acoustic output. The system calculates blood pressure by measuring the time-of-flight between ultrasound echoes reflected from arterial walls, converting this into a real-time diameter waveform correlated with pressure through vessel stiffness models. Bench-top experiments confirmed the linear relationship, and simulations highlighted that wearable systems can lose up to 60% signal strength with just 1 mm of misalignment—a problem the implanted design inherently avoids.
In an in vivo test, the PMUT system was implanted above the femoral artery of an adult sheep. It 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 pressure. These results demonstrate the device's stable coupling and accurate long-term performance, achieving the precision required for clinical use without the drawbacks of cuffs or fragile wearables.
The implications of this technology are substantial for healthcare and digital health platforms. By providing continuous, high-fidelity cardiovascular data, it could support long-term hypertension management, enable early detection of cardiovascular abnormalities, and offer clinicians richer data than periodic measurements allow. Its stability against tissue growth, motion, and environmental interference makes it suitable for integration into preventive care strategies. Future advancements, such as beamforming to mitigate positional shifts and data-driven analytics for individualized risk prediction, could further expand its clinical utility. This development represents a significant step toward reliable, unobtrusive continuous monitoring, potentially reducing cardiovascular risks through more effective management and real-time insights.
