Session: 16-01-01: Poster Session: NSF-Funded Research (Grad & Undergrad)

Paper Number: 97029

97029 - Investigation of Acoustic Pressure Patterning in Through-Wall Ultrasound Power Transfer Systems 

Ultrasound Power Transfer (UPT) systems have recently gained interest due to their capabilities in contactless energy transfer. Such a system preserves the structural integrity and enables wireless powering of sensors or receives in hard-to-reach components or in systems where extending wires is not safe such as spent fuel casks. The efficiency of such systems can be significantly enhanced through patterning or focusing the acoustic energy at the spots where receivers are located. This can be achieved by using acoustic holograms. Holograms can also be useful for many medical applications where wave focusing is required to stimulate targeted cells. The basis of holography is to manipulate the wavefront using a predesigned thickness pattern that introduces a relative phase shift in a way that allows that wavefront to be reconstructed by wave interference. In the past few years, researchers focused on analyzing wave patterning in homogeneous fluid mediums. Elastic waves manipulation through multilayer solid structures remains a challenge for enhancing the overall efficiency and locally charging sensors or devices. Unlike homogenous mediums, wave propagation through inhomogeneous multilayer structures induces wave reflections at the boundaries that need to be accounted for when designing the hologram. In this paper, we aim to develop an efficient UPT system using an acoustic transducer that emits ultrasound waves through a metal wall barrier. An acoustic holographic lens is attached to the metal wall to focus the acoustic wave to a desired piezoelectric receiver or group of receivers to power an external electric circuit. Towards this, a three-dimensional propagation finite element model is developed to simulate the system, and a genetic algorithm-based optimization is used to design the lens. The resulted hologram is then 3D-printed through direct metal laser melting with high resolution and attached to the transducer using water as a coupling medium. Experiments are conducted to verify our approach and to show the capability of holograms to pattern the elastic waves and achieve high power efficiency. The effects of the system’s parameters, including the epoxy coupling layer and operating frequency on the performance, are also investigated. As a result, we show a significant reduction in the lost energy and hence an increase in the overall efficiency with the presence of acoustic holograms in UPT systems.

Acknowledgments: This work is supported by NSF grants Award No. ECCS 1711139, IIP 1738689 (Phase II IUCRC Virginia Tech: Center for Energy Harvesting Materials and Systems), and Virginia Tech ICTAS Junior Faculty Award, which are gratefully acknowledged.

Presenting Author: Moustafa Sayed Ahmed Virginia Tech

Presenting Author Biography: Moustafa Sayed Ahmed is a second-year Ph.D. student at the Mechanical Engineering department at Virginia Tech. His research interest focuses on acoustics and vibration.

Authors:

Moustafa Sayed Ahmed Virginia Tech
Ahmed Sallam Virginia Tech
Shima Shahab Virginia Tech