Flexible ultrasound transducers (FUTs), capable of conforming to irregular surfaces, have become a research hotspot in the field of medical imaging. With these transducers, high-quality ultrasound images can be obtained only if strict design criteria are fulfilled. Moreover, the relative positions of array elements must be determined, which are important for ultrasound beamforming and image reconstruction. These two major characteristics present great challenges to the design and fabrication of FUTs compared to that for traditional rigid probes. In this study, an optical shape-sensing fiber was embedded into a 128-element flexible linear array transducer to acquire the real-time relative positions of array elements to produce high-quality ultrasound images. Minimum concave and convex bend diameters of approximately 20 and 25 mm, respectively, were achieved. The transducer was flexed 2000 times, and yet no obvious damage was observed. Stable electrical and acoustic responses confirmed its mechanical integrity. The developed FUT exhibited an average center frequency of 6.35 MHz, and average −6-dB bandwidth of 69.2%. The array profile and element positions measured by the optic shape-sensing system were instantly transferred to the imaging system. Phantom experiments for both spatial resolution and contrast-to-noise ratio proved that FUTs can maintain satisfactory imaging capability despite bending to sophisticated geometries. Finally, color Doppler images and Doppler spectra of the peripheral arteries of healthy volunteers were obtained in real time.

In this work, a flexible and stretchable ultrasonic transducer array consisting of 3 x 3 elements is proposed to achieve conformal contact with various nonplanar complex surfaces. The array is formed by integrating rigid piezoelectric ceramics with serpentine hinges in a single-layered configuration and encapsulated by compliant elastomers. The addressable electrodes arrangement allows the use of a small number of connecting wires to excite each element in the array. The developed ultrasonic transducer has a resonant frequency of 1.91 MHz and the initial acoustic characterization is demonstrated. The serpentine electrodes can be stretched up to 33% without failure and the array exhibits excellent flexibility of bending, folding, twisting, and rolling up, indicating its reliable electrical connection and stable mechanical property. Moreover, the performance of the array attached to curved surfaces, human skins, and medical catheters is also demonstrated. The results indicate a convenient and robust method to achieve the preparation of a flexible and stretchable ultrasonic transducer array, which extends conventional rigid ultrasonic transducers to future wearable applications.

Ultrasound imaging offers a non-invasive, 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 characterised using standard methods, with large tensile strains (≥110%), high flexibility (R ≥1.4 mm) and light weight (≤1.58 g) to meet the needs of wearable devices. Center frequency and -6dB bandwidth are approximately 5.3MHz and 66.47%, respectively. Images of the commercial anechoic cyst phantom yielded an axial and lateral resolution (depths of 10 mm to 70 mm) of approximately 0.31mm and 0.46mm, 0.34mm and 0.84mm 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.

Traditional traveling wave robots have strict requirements on the operating interface due to the fact that they usually only work on smooth and flat surfaces, holding the disadvantages of poor load capacity and complex driving mode, and limiting their application range. In order to overcome the above problems, a novel traveling wave piezoelectric actuated wheeled robot is proposed in this study. The robot is composed of a bonded-type piezoelectric actuator and wheel mechanisms. Rotating traveling wave can be produced in the annular parts of the piezoelectric actuator to drive the wheel mechanisms. In order to study the dynamic characteristics of the piezoelectric actuator, an electromechanical coupling model is developed by using the transfer matrix method. Then the prototype of the piezoelectric actuator is fabricated and assembled, and its vibration characteristics are measured to confirm the feasibility of the developed transfer matrix model. Finally, performance evaluation investigations of the proposed traveling wave piezoelectric actuated wheeled robot are conducted. Under the excitation voltages of 350 V _pp and the phase difference of 90°, the robot prototype achieved a step climbing angle of 75°, a maximum no-load velocity of 136.8 mm s ⁻¹ , and a maximum payload of 320 g. The proposed traveling wave piezoelectric actuated wheeled robot presents expected terrain adaptability and obstacle climbing capability.

The V-shaped ultrasonic motor with two Langevin-type transducers has shown potential applications in the precision engineering, aerospace, bioengineering, and other fields. However, there is a lack of analytical models to predict the mechanical characteristics and to design the controller. In this paper, a dynamic model of the V-shaped motor is established, mainly including the analytical model of the V-shaped stator, the friction model between the stator and mover, and the dynamic model of the mover. Using the dynamic model, the mechanism of the frictional drive is revealed; dynamic characteristics of the stator and the mover are analyzed; mechanical characteristics are predicted. The simplified control model is established upon the dynamic model avoiding the highly nonlinear problem caused by the contact and friction. It is experimentally shown that the dynamic model not only can be used to predict and evaluate the performance (displacement, speed, thrust) of the motor, but also can be used as the basis for controller design.