Lensing in the Ultrasonic Domain using Negative Refraction Induced by Material Contrast

Lensing in the Ultrasonic Domain using Negative Refraction Induced by Material Contrast

Abstract The focusing of ultrasound using topographic lenses, typically made of plates with step changes that cause an interaction between forward- and backward-propagating guided waves, has been widely studied in recent years. However, such ‘step-change’ lenses require precise machining and moreove...

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Autores principales: C. T. Manjunath, Prabhu Rajagopal
Formato: article
Lenguaje:EN
Publicado: Nature Portfolio 2019
Materias:
Medicine
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Science
Q
Acceso en línea:https://doaj.org/article/8944dc65af074ba4aad1ce1ce501626c
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spelling oai:doaj.org-article:8944dc65af074ba4aad1ce1ce501626c2021-12-02T15:08:32ZLensing in the Ultrasonic Domain using Negative Refraction Induced by Material Contrast10.1038/s41598-019-42655-32045-2322https://doaj.org/article/8944dc65af074ba4aad1ce1ce501626c2019-04-01T00:00:00Zhttps://doi.org/10.1038/s41598-019-42655-3https://doaj.org/toc/2045-2322Abstract The focusing of ultrasound using topographic lenses, typically made of plates with step changes that cause an interaction between forward- and backward-propagating guided waves, has been widely studied in recent years. However, such ‘step-change’ lenses require precise machining and moreover, the thick-thin structure can be unstable during deployment in practical inspection applications. The work reported here follows from the insight that perhaps any approach to induce a mismatch in acoustical impedance as achieved by the step-change can also lead to focusing of ultrasonic guided waves. By carefully choosing the impedance pairing, a novel material contrast lens stacking Aluminium and Molybdenum plates in series is shown to achieve focusing of ultrasound through negative refraction. The interface between the two metals causes the interaction of the forward-propagating second symmetric Lamb mode S2 into the backward- propagating first symmetric S2b. The focusing of Lamb waves is demonstrated using numerical simulations validated by experiments. Comparison with a simple Aluminium-Aluminium plate combination brings out the underlying physics of focusing using the proposed material contrast lens. Simulation results showing super-resolution imaging using the proposed material contrast lens  are also presented, demonstrating the power of the proposed approach. This report opens up the possibilities of developing new lensing devices for use in medical imaging and nondestructive evaluation, among other possible applications.C. T. ManjunathPrabhu RajagopalNature PortfolioarticleMedicineRScienceQENScientific Reports, Vol 9, Iss 1, Pp 1-8 (2019)
institution DOAJ
collection DOAJ
language EN
topic Medicine
R
Science
Q
spellingShingle Medicine
R
Science
Q
C. T. Manjunath
Prabhu Rajagopal
Lensing in the Ultrasonic Domain using Negative Refraction Induced by Material Contrast
description Abstract The focusing of ultrasound using topographic lenses, typically made of plates with step changes that cause an interaction between forward- and backward-propagating guided waves, has been widely studied in recent years. However, such ‘step-change’ lenses require precise machining and moreover, the thick-thin structure can be unstable during deployment in practical inspection applications. The work reported here follows from the insight that perhaps any approach to induce a mismatch in acoustical impedance as achieved by the step-change can also lead to focusing of ultrasonic guided waves. By carefully choosing the impedance pairing, a novel material contrast lens stacking Aluminium and Molybdenum plates in series is shown to achieve focusing of ultrasound through negative refraction. The interface between the two metals causes the interaction of the forward-propagating second symmetric Lamb mode S2 into the backward- propagating first symmetric S2b. The focusing of Lamb waves is demonstrated using numerical simulations validated by experiments. Comparison with a simple Aluminium-Aluminium plate combination brings out the underlying physics of focusing using the proposed material contrast lens. Simulation results showing super-resolution imaging using the proposed material contrast lens  are also presented, demonstrating the power of the proposed approach. This report opens up the possibilities of developing new lensing devices for use in medical imaging and nondestructive evaluation, among other possible applications.
format article
author C. T. Manjunath
Prabhu Rajagopal
author_facet C. T. Manjunath
Prabhu Rajagopal
author_sort C. T. Manjunath
title Lensing in the Ultrasonic Domain using Negative Refraction Induced by Material Contrast
title_short Lensing in the Ultrasonic Domain using Negative Refraction Induced by Material Contrast
title_full Lensing in the Ultrasonic Domain using Negative Refraction Induced by Material Contrast
title_fullStr Lensing in the Ultrasonic Domain using Negative Refraction Induced by Material Contrast
title_full_unstemmed Lensing in the Ultrasonic Domain using Negative Refraction Induced by Material Contrast
title_sort lensing in the ultrasonic domain using negative refraction induced by material contrast
publisher Nature Portfolio
publishDate 2019
url https://doaj.org/article/8944dc65af074ba4aad1ce1ce501626c
work_keys_str_mv AT ctmanjunath lensingintheultrasonicdomainusingnegativerefractioninducedbymaterialcontrast
AT prabhurajagopal lensingintheultrasonicdomainusingnegativerefractioninducedbymaterialcontrast
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