A Flexible Ultrasound Array for Local Pulse Wave Velocity Monitoring

Abstract

Pulse wave velocity (PWV) measured at a specific artery location is called local PWV, which provides the elastic characteristics of arteries and indicates the degree of arterial stiffness. However, the large and cumbersome ultrasound probes require an appropriate sensor position and pressure maintenance, introducing usability constraints. In this paper, we developed a light (0.5 g) and thin (400 μm) flexible ultrasound array by encapsulating 1–3 composite piezoelectric transducers with a silicone elastomer. It can capture the distension waveforms of four arterial positions with a spacing of 10 mm and calculate the local PWV by multi-point fitting. This is illustrated by in vivo experiments, where the local PWV value of five normal subjects ranged from 3.07 to 4.82 m/s, in agreement with earlier studies. The beat-to-beat coefficient of variation (CV) is 12.0% ± 3.5%, showing high reliability. High reproducibility is shown by the results of two groups of independent measurements of three subjects (the error between the mean values is less than 0.3 m/s). These properties of the developed flexible ultrasound array enable the bandage-like application of local PWV monitoring to skin surfaces.

Recent Advances in Materials, Devices and Algorithms Toward Wearable Continuous Blood Pressure Monitoring

“…Typically, such transducer arrays integrate multiple piezoelectric composite units for the generation and reception of ultrasound signals; through the utilization of advanced fabrication techniques and the implementation of a multilayered structure, the transducer can achieve high levels of lightness and thinness (Figure 9A). 63 Consequently, the ultrasound transducer array not only mitigates the bulky nature associated with traditional probes but also possesses the ability to flex or twist, thereby effectively accommodating the deformations of human skin. In conjunction with recent advancements in flexible electronics, certain research has incorporated flexible electronics technology into the fabrication of transducer arrays (Figure 9B,C).…”

Towards ultrasound wearable technology for cardiovascular monitoring: from device development to clinical validation

“…In summary, CMUTs and PMUTs offer advantages over bulk PZTs, including miniaturization, integration, and low-cost high-volume production. Still, bulk PZTs remain widely used for portable cardiovascular monitoring [29,48,70,[80][81][82] due to their mature and well-known technology.…”

Recent Advances in Flexible Ultrasonic Transducers: From Materials Optimization to Imaging Applications

“…The addressable electrode arrangement is designed to effectively excite and connect nine units and comply with the single-layered “island-bridge” layout [ 17 ], as shown in Figure 5c. Xu et al fabricated a multilayer material composed of 20 µm thick Cu foil and 10 µm thick PI film, used the laser to pattern serpentine-shaped electrical conductors, peeled off the excess Cu-PI layer and finally used it as the flexible electrical conductors for flexible US transducers, as shown in Figure 2 c [ 44 ]. Liu et al used photolithography and etching to make Cu foil into a serpentine-shaped structure to be used as the flexible electrical conductors, as shown in Figure 2 b [ 42 ].…”