Scientists have discovered a better method that is 100% effective in terms of storing a releasing mechanical wave. Through a proof-of-concept experiment, the scientists clearly proved how possible it is to capture and store mechanical wave and then guiding it to a specific location without any energy loss.
This is a breakthrough that can potentially improve our capability to manipulate waves, which could have implications in a wide range of fields.
The set up of the experiment consisted of an elongated, carbon steel bar bearing a cavity in the middle and a twin-actuators at each end. Through this experiment, two mechanical waves were produced by the two actuators that travelled in two opposite directions.
Andrea Alù, lead writer of the study from the City University of New York, addressing the Newsweek said, “A mechanical wave is similar to a wave propagating on the surface of the ocean, but it carries vibrations that travel in solid materials…A good example is a wave travelling along a guitar string.”
“Typically, storing energy in resonant cavities is inefficient, and it is challenging to accumulate signals and release it on-demand at a later time,” she said. “Our experiment proves that it is possible to efficiently store energy in a given region and then release it on-demand towards a preferred direction.”
Also, the research team realized the materials that can absorb energy may be designed to extract the entire “impinging energy” originating from a source.
This phrase basically means that all the energy is being carried by the wave. Naturally, when a stream is absorbed by a material which it is impinging, that is, gets into contact with, some of its energy is definitely lost.
“[Absorbing materials] transform this energy in other forms. Here, we wanted to mimic the absorption process in terms of efficiency, but using a system that preserves the energy in the same form, and can then release it on demand,” Alù said. “Two years ago we showed, theoretically, that it is possible to achieve this goal by controlling and tailoring the waves’ time evolution so that when they came in contact with non-absorbing materials, they would efficiently pile up in the material without reflections as if they were absorbed.”
“We named this concept of coherent virtual absorption. This method prevents the wave impinging on the structure from escaping, and it gets efficiently trapped inside as if it were being absorbed. The stored wave could then be released on demand,” she said.
In the experiment, the team produced two mechanical waves that travelled in two opposite directions from the carbon steel bars, and carefully controlled their time variations that the cavity retained all of its impinging energy.
“Then, by stopping the excitation or detuning one of the two signals from the other, we were able to control the release of the stored energy and send it towards the desired direction,” Alù said.
According to the scientists, the results of this research could result in great advancements in several areas
“Our experiment with mechanical waves shows a new degree of control of vibrations, which are commonly used for monitoring the integrity of structures like bridges, so our work can improve the efficiency of these integrity control systems,” Alù said.
“In addition, we are currently exploring the application of similar concepts to other types of waves, including light. We envision efficient devices for optical computing and quantum computing based on similar principles, and improving the efficiency of wireless charging, memories and switches,” she said.