Skin-conformal PMN-PT ultrasonic sensor for cuffless blood pressure sensing via eutectic solder integration

Area of Science:

• Biomedical Engineering
• Materials Science
• Cardiovascular Technology

Background:

• Wearable ultrasonic systems offer noninvasive cardiovascular monitoring.
• Challenges exist in integrating flexible piezoelectric materials for skin-conformal arrays.

Purpose of the Study:

• To develop a flexible ultrasonic transducer array for continuous blood pressure monitoring.
• To address challenges in mechanical stretchability, acoustic fidelity, and scalability.

Main Methods:

• Fabrication of a 5x4 ultrasonic transducer array using 1-3 lead magnesium niobate-lead titanate (PMN-PT) composite elements.
• Utilized dual-sided eutectic solder bonding with Sn-Bi alloy for low-temperature, non-depolarizing attachment.
• Characterized the array's performance, including center frequency (6.0 MHz) and acceptance angle (45°).

Main Results:

• The flexible array achieved accurate tracking of vessel diameters and real-time blood pressure estimation via time-of-flight simulations and in vitro testing.
• Systolic and diastolic pressure measurements were within 4 mmHg of a commercial reference sensor.
• Demonstrated feasibility of scalable, flexible ultrasound for wearable hemodynamic sensing.

Conclusions:

• The developed ultrasonic transducer array shows potential for next-generation point-of-care diagnostics.
• Highlights the viability of flexible ultrasound systems for wearable hemodynamic sensors.
• Enables real-time vascular dynamics assessment without cuff-based measurements.