UC San Diego

Ultrasonic imaging has been implemented as a powerful tool for noninvasive subsurface inspections of both structural and biological media. Current ultrasound probes are rigid and bulky and cannot readily image through nonplanar three-dimensional (3D) surfaces. However, imaging through these complicated surfaces is vital because stress concentrations at geometrical discontinuities render these surfaces highly prone to defects. From the aspect of monitoring of the human vital signs, although current ultrasonic technologies allow non-invasive deep tissue observation, unstable coupling with the tissue surface resulting from the bulkiness and rigidity of conventional ultrasound probes introduces usability constraints.Based on those motivations, reports a stretchable ultrasound probe that can conform to and detect nonplanar complex surfaces. The probe consists of a large array of piezoelectric transducers that exploit an “island-bridge” layout with multilayer electrodes, encapsulated by thin and compliant silicone elastomers. The stretchable device can conform to the nonplanar surfaces of industrial components or human skin and enables non-invasive, continuous and accurate testing, which should facilitate its use in a variety of structural health monitoring and clinical environments. In Chapter One, the introduction of the stretchable ultrasonic device and the current problems presented in this field will be introduced and discussed. The probe design and fabrication for different applications are introduced. Our work presents the first stretchable ultrasonic arrays for different types of measurement and monitoring. In Chapter Two, the acoustic and mechanical properties of the device will be introduced. Performances of the device for elastography and B-mode imaging will also be explained in detail. In Chapter Three, the first application of the device for nondestructive evaluation will be demonstrated. The device performance is demonstrated by reconstructing defects in 3D space with high spatial resolution through flat, concave, and convex surfaces. The results hold great implications for applications of ultrasound that require imaging through complex surfaces. In Chapter Four, a variety of applications for monitoring of human vital signs, such as blood pressure waveform, tissue stiffness, and organ anatomy, are demonstrated, which opens up opportunities for wearable diagnostics in a variety of clinical environments.