Design, modeling and fabrication of polymer-based Capacitive Micromachined Ultrasonic Transducers (polyCMUTs)

Abstract

Ultrasound imaging is the most widely used medical imaging modality in the world. Modern ultrasound systems still rely on the same piezoelectric-based technology since their creation in the 1930s. Despite their mature technology, they are expensive to fabricate, difficult to create 2D arrays and cannot be miniaturized. Capacitive Micromachined Ultrasonic Transducers (CMUTs) are considered the replacement of piezoelectric transducers given their high bandwidth, ease of integration with electronics and miniaturization. The main focus of this dissertation involves the simulation, fabrication and characterization of polymer-based CMUTs (polyCMUTs). A new fabrication process involving inexpensive polymer materials and minimum fabrication steps was developed. The fabrication procedure allows the creation of biocompatible ultrasound chips in a few hours and with costs well below $100 USD, having a performance comparable to current commercial devices. The fabricated polyCMUTs exhibit a phenomenon termed “pre-biasing”, which allowed the operation of polyCMUTs as passive devices (no external power needed). The first B-mode ultrasound image in the world created using polyCMUTs is also presented. As a future plan, the development of a low-cost wearable ultrasound health monitoring system is conceived.