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The breakthrough enables storage and release of mechanical waves without loss of energy



  Breakthrough allows storage and release of mechanical waves without loss of energy.
Experimental set-up consisting of waveguide strip with cavity and side channels. The excitation of the elastic waves propagating along the rod is by piezoelectric actuators at the two ends of the system. Picture credits: Giuseppe Trainiti, Georgia Tech

Light and sound waves provide the basis for energy and signal transport, and are fundamental to some of our most basic technologies, from mobile phones to motors. However, scientists have not yet developed a method that allows them to store a wave unscathed indefinitely and then direct it to a desired location when needed. Such a development would greatly facilitate the manipulation of waves for a variety of desired applications, including power generation, quantum computing, structural integrity monitoring, information storage, and more.

In a newly published article in Science Advances a group of researchers led Andrea Alù, founding director of the Photonics Initiative at the Graduate Center's Advanced Science Research Center (ASRC), CUNY, and Massimo Ruzzene, a professor of Aeronautical engineering at Georgia Tech has experimentally demonstrated that it is possible to efficiently capture and store an intact wave and then direct it to a specific location.

"Our experiment shows that unconventional excitation forms open up new possibilities to gain control over wave propagation and scattering," said Alù. "By carefully adjusting the time-dependence of the excitation, it is possible to cause the wave to be efficiently stored in a cavity and then release it in the desired direction as needed."

Methodology [1

9659005] To achieve their goal, scientists needed to find a way to alter the fundamental interaction between waves and materials. When a light or sound wave strikes an obstacle, it is either partially absorbed or reflected and scattered. The absorption process involves the immediate transformation of the wave into heat or other forms of energy. Materials that can not absorb waves only reflect and scatter them. The goal of the researchers was to find a way to mimic the absorption process without transforming the wave into other forms of energy and instead storing it in the material. This concept, introduced theoretically by the ASRC group two years ago, is known as coherent virtual absorption.

To prove their theory, the researchers had to adjust the temporal evolution of the waves to come into contact with non-waves-absorbing materials that would not be reflected, scattered or transmitted. This would prevent the wave impinging on the structure from leaking, and it would be efficiently trapped inside as if it were being absorbed. The stored wave could then be released when needed.

During their experiment, the researchers spread two mechanical waves in opposite directions along a waveguide rod of carbon steel containing a cavity. The time variations of each wave have been carefully controlled to ensure that the cavity retains all of the incident energy. By then stopping the excitement, or detuning one of the waves, they managed to control the release of stored energy and steer it in a desired direction as needed.

"While conducting our proof of concept experiment with Elastic Our findings also apply to radio waves and light and offer exciting perspectives for efficient energy production, wireless energy transfer, low-energy photonics, and generally improved wave propagation control," said Ruzzene.


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Further information:
"Coherent Virtual Absorption of Elastodynamic Waves" Science Advances (2019). DOI: 10.1126 / sciadv.aaw3255, https://advances.sciencemag.org/content/5/8/eaaw3255

Provided by
CUNY Advanced Science Research Center




Quote :
Breakthrough enables storage and release of mechanical waves without loss of energy (2019, 30th August)
retrieved on August 31, 2019
from https://phys.org/news/2019-08-breakthrough-enables-storage-mechanical-energy.html

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