Flexible Stencil-Printed Piezoelectric Transducer Arrays for Catheter Based Ultrasound Applications

In this paper, we present flexible piezoelectric transducer arrays using composite piezoelectric materials at a low process temperature $(< 140^{\circ}\mathrm{C})$ for use in intravascular ranging and lumen sizing applications. Transducer arrays with a size of $4\mathrm{x}1.5\mathbf{mm}^{2}$ total area and $50\mu \mathrm{m}$ thickness are formed on polyimide substrates and wrapped around 9 Fr (3 mm) catheters without any surface deformations. Additionally, in terms of flexibility, different dimension transducers are examined through bending tests showing that $4\mathrm{x}4\text{mm}^{2}$ and $2\mathrm{x}2\text{mm}^{2}$ transducers can be bent as tight as 2 mm and 1.2 mm radius of curvature without any detrimental effects. Furthermore, transducer array and electrical interconnects can be packed in a way to achieve a sleeve like structure for microcatheters that requires minimal modification for integration to different devices. Acoustic performance of transducer arrays is characterized through hydrophone and pulse-echo measurements. Acoustic response of transducer arrays before and after wrapping and before and after outer layer implementation showed no significant changes. The results indicate that these devices can be suitable for various medical sensing applications such as ranging and lumen sizing in the 5–10 MHz range with broadband acoustic response with flexibility and ease of integration.