Physicists map new route to control sound in thin films

A theoretical path to make synthetic composite skinny movies through which sound waves may be stopped, reversed and even saved for later use has been achieved by College of Oregon physicists.

Postdoctoral researcher Pragalv Karki and Jayson Paulose, an assistant professor of physics, centered on mechanical vibrations in skinny elastic plates, the constructing blocks for his or her proposed design of artificial movies generally known as metamaterials, utilizing theoretical and computational evaluation. In addition they developed an easier mannequin consisting of springs and lots more and plenty to reveal the sign manipulation skill.

“There have been lots of mechanisms that may information or block the transmission of sound waves by means of a metamaterial, however our design is the primary to dynamically cease and reverse a sound pulse,” Karki stated.

The interaction between bending stiffness and international stress, two bodily parameters governing sound transmission in skinny plates, is on the coronary heart of their mechanism. Whereas bending stiffness is a fabric property, international stress is an externally controllable parameter of their system.

Karki and Paulose of the UO Division of Physics and Institute for Elementary Science described their mechanism, which they name dynamic dispersion tuning, in a paper revealed on-line March 29 within the journal Bodily Evaluate Utilized.

“In case you throw a stone onto a pond, you see the ripples,” Karki stated. “However what should you threw the stone and as an alternative of seeing ripples propagating outward you simply see the displacement of the water going up and down on the level of influence? That is much like what occurs in our system.”

The flexibility to govern sound, gentle or every other wave in artificially made metamaterials is an energetic space of analysis, Karki stated.


Optical metamaterials, which exhibit properties akin to a adverse refractive index not doable with standard supplies, have been initially developed to regulate gentle in ways in which may very well be used to create invisibility cloaks and superlenses. Their use is being explored in numerous purposes akin to aerospace and protection, shopper electronics, medical gadgets and vitality harvesting.

Acoustic metamaterials are often static and unchangeable, so how you can tune their properties is an ongoing problem, Karki stated. Different analysis teams have proposed a number of methods, akin to utilizing origami-inspired designs or magnetic switching.

“In our case, the tunability comes from the power to vary the stress of the drumlike membranes in actual time,” Karki stated.

Extra inspiration, Karki and Paulose famous, got here from analysis within the UO lab of physicist Benjamín Alemán that was revealed in Nature Communications in 2019. Alemán’s group unveiled a graphene nanomechanical bolometer, a drumlike membrane that may detect colours of sunshine at excessive speeds and excessive temperatures. The method exploits a change in international stress.

Whereas the mechanism within the new paper was recognized theoretically and must be confirmed in lab experiments, Karki stated, he’s assured the method will work.

“Our mechanism of dynamic dispersion tuning is impartial of whether or not you’re utilizing acoustic, gentle or digital waves,” Karki stated. “This opens up the potential of manipulating indicators in photonic and digital programs as effectively.”

The method, he stated, may embrace improved acoustic sign processing and computation. Designing acoustic metamaterials primarily based on graphene, akin to these in Alemán’s lab, may very well be helpful in such applied sciences as wave-based computing, micromechanical transistors and logic gadgets, waveguides, and ultrasensitive sensors.

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Materials supplied by University of Oregon. Authentic written by Jim Barlow. Observe: Content material could also be edited for model and size.