Reconfigurable Acoustic Metamaterials Inspired by Sharks

Innovation: Academia

University of Southern California

2020

Image: Laura College / Unsplash / CC BY SA - Creative Commons Attribution + ShareAlike

Capture, Absorb, or Filter Energy

Energy is naturally available in many forms, including kinetic, potential, thermal, elastic, radiant, chemical, and more. All living systems require energy to carry out their many activities, and have developed strategies appropriate to one or more of those forms. For example, some plants maximize their surface area available for capturing radiant energy from the sun while others have strategies to focus scattered light onto photosynthesizing areas.

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Transform Magnetic Energy

Magnetic energy is the energy in a magnetic field, generated by electric currents. Since all organisms and the Earth itself generate electrical fields, this energy can be used by organisms in several ways. For just two examples, electro-magnetic receptors may sense the presence or activity of other organisms and convert the charge to a chemical signal, or embedded magnetic crystals may align with the north/south axis of the planet, converting the magnetic energy into kinetic energy that the surrounding cells respond to physically.

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Modify Energy State

The ability to modify the energy state of different particles can be useful for harnessing the energy organisms need to survive. Explore how different organisms use these abilities to adapt to their different environments.

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Acoustic metamaterial from the University of Southern California uses magnets to shift acoustic states and alter transmission.

Benefits

Flexible
Tunable
Responsive

Applications

Electronic devices
Surveillance

UN Sustainable Development Goals Addressed

Goal 9: Industry Innovation & Infrastructure

The Challenge

Acoustic metamaterials are designed to control, direct and manipulate soundwaves as they pass through different mediums. They can be used to dampen or transmit sound within a structure, such as headphones or submarines. Traditional acoustic metamaterials have complex geometries and are made of metal or hard plastic. Once they are created, it is difficult to change their properties, limiting their use.

Innovation Details

Smart materials allow for multiple, changing properties within one structure. The smart acoustic metamaterial was inspired by the dual properties created by the dermal denticles on shark skin. It is made from rubber and magneto-sensitive nanoparticles. To make the nanoparticles responsive to acoustic transmission, researches had to be able to actively block or conduct acoustic input. They used Mie resonator pillar (MRP) arrays that are magnetically deformable. If the pillars are closer together, the acoustic wave is unable to pass through. If the pillars are further apart, the acoustic wave will easily pass through. External magnetic fields help to bend and unbend the pillars to achieve this type of ‘state switching’.

Watch how the acoustic smart material works

Biological Model

Fast-swimming sharks have skin denticles that are shaped like “V” trenches and aligned in the direction of fluid flow. The skin denticles can significantly reduce the flow drag because the V-shaped trenches are able to guide a turbulent flow to become laminate flow. The denticles are also able to bristle upwards up to 50 degrees above the horizontal. This allows them to block the backward flow of any turbulence that does arise, and then nearly instantly settle back down when the turbulence is broken and main flow resumes.

See Related Strategy

Biological Strategy

Scales Manipulate Flow

Sharks

Scales on sharks influence drag and thrust during swimming by manipulating fluid flow next to the body.

References

Journal article

Sharkskin-Inspired Magnetoactive Reconfigurable Acoustic Metamaterials

Research: A Science Partner Journal

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