Skin-Conformable Flexible and Stretchable Ultrasound Transducer for Wearable Imaging.

Ultrasound imaging offers a noninvasive, radiation-free method for visualizing internal tissues and organs, with deep penetration capabilities. This has established it as a crucial tool for physicians in diagnosing internal tissue pathologies and monitoring human conditions. Nonetheless, conventional ultrasound probes are often characterized by their rigidity and bulkiness. Designing a transducer that can seamlessly adapt to the contours and dynamics of soft, curved human skin presents significant technical hurdles. We present a novel flexible and stretchable ultrasound transducer (FSUT) designed for adaptability to large-curvature surfaces while preserving superior imaging quality. Central to this breakthrough is the innovative use of screen-printed silver nanowires (AgNWs) coupled with a composite elastic substrate, together ensuring robust and stable electrical and mechanical connections. Standard tensile and fatigue tests verify its durability. The mechanical, electrical, and acoustic properties of FSUTs are characterized using standard methods, with large tensile strains (≥110%), high flexibility ( R ≥ 1.4 mm), and lightweight ( ≤ 1.58 g) to meet the needs of wearable devices. Center frequency and -6-dB bandwidth are approximately 5.3 MHz and 66.47%, respectively. Images of the commercial anechoic cyst phantom yielded an axial and lateral resolution (depths of 10-70 mm) of approximately 0.31 and 0.46, and 0.34 and 0.84 mm, respectively. The complex curved surface imaging capabilities of FSUT were tested on agar-gelatin-based breast cyst phantoms under different curvatures. Finally, ultrasound images of the thyroid, brachial, and carotid arteries were also obtained from volunteer wearing FSUT.

Laser Scanning Guided Localization Imaging with a Laser-Machined Two-Dimensional Flexible Ultrasonic Array.

Advances in flexible integrated circuit technology and piezoelectric materials allow high-quality stretchable piezoelectric transducers to be built in a form that is easy to integrate with the body's soft, curved, and time-dynamic surfaces. The resulting capabilities create new opportunities for studying disease states, monitoring health/wellness, building human-machine interfaces, and performing other operations. However, more widespread application scenarios are placing new demands on the high flexibility and small size of the array. This paper provides a 8 × 8 two-dimensional flexible ultrasonic array (2D-FUA) based on laser micromachining; a novel single-layer "island bridge" structure was used to design flexible array and piezoelectric array elements to improve the imaging capability on complex surfaces. The mechanical and acoustoelectric properties of the array are characterized, and a novel laser scanning and positioning method is introduced to solve the problem of array element displacement after deformation of the 2D-FUA. Finally, a multi-modal localization imaging experiment was carried out on the multi-target steel pin on the plane and curved surface based on the Verasonics system. The results show that the laser scanning method has the ability to assist the rapid imaging of flexible arrays on surfaces with complex shapes, and that 2D-FUA has wide application potential in medical-assisted localization imaging.