Flexible and Stretchable Ultrasonic Transducer Array Conformed to Complex Surfaces

In this work, a flexible and stretchable ultrasonic transducer array consisting of 3 × 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.