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Massachusetts Institute of Technology - A new wrinkle in the control of waves

Flexible materials could provide new ways to manipulate sound and light

DCN Corp® - In the top pair of images, sound waves (blue and yellow bands) passing through a flat layered material are only minimally affected. In the lower images, when sound goes through a wrinkled layered material, certain frequencies of sound are blocked and filtered out by the material. Credit - Massachusetts Institute of Technology (MIT), USA and Felice FrankelFlexible and layered materials which are textured with nanoscale wrinkles could provide a new way of controlling the wavelengths and distribution of waves - no matter whether there of sound or light. The process has been developed by researchers at MIT, which could eventually find applications for the non-destructive testing of materials-to-sound suppression. Also, it could provide new insights in biological systems as well as possibly provide a path for new diagnostic tools.

The research has been described in the journal Physical Review Letters - authored by an MIT Postdoc Stephan Rudykh and Mary Boyce. Boyce is a former professor of Mechanical Engineering at MIT and now is the dean of the Fu Foundation School of Engineering and Applied Science at Columbia university.

Whilst some materials are known to have properties which affect the propagation of light and sound, unfortunately, in most instances such properties are fixed when the material is made or grown, and so are extremely difficult to alter afterwards. However, at the same time the layered materials can have changing properties - for example the ability to "tune" a material to filter out specific colours of light - which can be as straightforward as stretching the flexible material.

Rudykh states - "These effects are highly tunable, reversible, and controllable," - and - "For example, we could change the colour of the material or potentially make it optically or acoustically invisible."

The materials can be synthesised through a layer-by-layer deposition process, and subsequently refined by researchers at MIT and elsewhere, which can be controlled to a high precision. The process enables the thickness of each layer to be determined to within a fraction of a wavelength of light. The material was then compressed, thus, creating a series of precise wrinkles whereby the distance in-between can scatter selected frequencies of waves.

Rudykh states that surprisingly the effects work even on materials where the alternating layers have the same densities - "We can use polymers with very similar densities and still get the effect," - and - "How waves propagate through a material, or not, depends on the micro-structure, and we can control it."

Rudykh continues to state that by designing the micro-structure to produce a desired set of effects, then altering the properties be deforming the material - "We can actually control these effects through external stimuli," - and "You can design a material that will wrinkly to a different wavelength and amplitude. If you know you want to control a particular range of frequencies, you can design it that way."

And he (Rudykh) continues with stating that the computer modelling research could also provide insights into the properties of natural biological materials - "Understanding how the waves propagate through biological tissues could be useful for diagnostic techniques."

Currently diagnostic techniques for certain cancers involve a painful and invasive procedure. Ultrasound can provide the same information non-invasively, but, unfortunately, today's ultrasound systems lack sufficient resolution. So, the MIT research with wrinkled materials could lead to more precise controlling of the ultrasound waves, and so provide systems with improved resolution.

Interestingly the system could also be employed in sound cloaking, which is an advanced form of noise cancellation whereby outside sound could be completely blocked from a certain volume of space rather than at a single spot, as is the case with noise-cancelling headphones.

Rudykh provides a conclusion stating - "The micro-structure we start with is very simple," - and is based on a commonly known layer-by-layer manufacturing process - "From this layered material, we can extend to more complicated micro-structures, and get effects you could never get" via conventional materials. It is hoped, that such systems could be employed to control a variety of effects in the propagation of light, sound, and even heat. Original article available here

Please Note the technology, above, will be patented, and the researchers are in ongoing discussions with companies about possible commercialisation opportunities.

As with similar type of USA / MIT studies, the future potential of nano fabrication techniques has been handsomely sold.  As stated previously, DCN Corp strongly believes it can supersede, by providing a superior nano controlling process.  Going forward, if you and/or your colleagues are interested in making DCN Corp's alternative process reality - please ensure to contact the company as soon as practicably possible.