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

Paper Number: 100057

100057 - Generating Multi-Pixel Thermal Images Through an Acoustic-Thermal Effect 

In this study, we attempted to systematically integrate the acousto-thermal effect and acoustic holography to explore the feasibility of generating controlled thermal fields in a tissue-mimicking material. To enable this capability, our method firstly generates multiple acoustic focal points by using an acoustic hologram-based lens and then constructs a thermal field with multiple elevated-temperature areas based on the acousto-thermal effect. To design the acoustic lens, multiple points are distributed on a constraint plane, which is used as the input for determining the desired phase map based on an iterative phase propagation approach. To characterize the performance of our hologram for generating an acoustic field with concentrated energy at multiple points, on one hand, numerical simulations were performed. On the other hand, experiments were performed by using a 3D printed hologram to generate multiple acoustic focal points and further enable the acousto-thermal effect at multiple target locations of a phantom slice. The thermal image recorded by an infrared camera shows multiple elevated-temperature areas. Moreover, the locations of these elevated-temperature areas agree with the locations of acoustic focal points. We expect this study can contribute to the noncontact control of thermal fields for biomedical applications.

The acousto-thermal effect, which is induced by the acoustic energy dissipation, has been used for tissue ablation, nondestructive evaluation, and material synthesis. To leverage the acousto-thermal effect, most studies use focused acoustic waves with concentrated energy for enabling local temperature increases. However, generating arbitrarily shaped thermal fields based on the acousto-thermal effect is still a challenging problem. Therefore, in this study, we investigated the feasibility of leveraging acoustic holography for generating arbitrarily shaped acoustic fields and further enabling the construction of arbitrarily thermal fields. Particularly, this study focuses on the simultaneous generation of multiple elevated-temperature areas. Moreover, we experimentally investigated the acoustic wave-induced transient temperature field changes by capturing a series of thermal images using an infrared camera. The experimental results show that our method can simultaneously increase the temperatures in multiple desired areas. Moreover, the center locations of these areas agree with the locations with focused acoustic energy.

Specifically, our simulation results show that acoustic waves passing through a hologram can be transformed to generate multiple acoustic focuses in the desired target plane. Because of the acousto-thermal effect, the multiple acoustic focuses can lead to a thermal field containing multiple increased temperature areas that correspond to the acoustic focusing areas. On one hand, through acoustic field scanning, we characterized the generated acoustic pressure fields that agree with our acoustic simulation results. On the other hand, through acousto-thermal experiments, we characterized the acoustic wave-induced thermal fields. Our results show that multiple increased temperature areas can be simultaneously generated. In the future, we will perform more theoretical and experimental studies to better understand the generation of complex thermal fields using acoustic waves as well as enhance the resolution of generated thermal fields.

Presenting Author: Teng Li Mississippi State University

Presenting Author Biography: Teng Li, is a Ph.D. student in the department of aerospace engineering, at Mississippi State University.

Authors:

Teng Li Mississippi State University
Zhenhua Tian Viginia Polytechnic Institute and State University