Articles
Engineers from Swiss materials research laboratory Empa and University ETH Zurich say that their prototype metamaterial could “change the world of mechanics forever” and is the first step towards the development of mechanical components with programmable properties.
The prototype is a 1m x 1cm aluminium plate, 1mm thick. This sheet-metal strip can vibrate at different frequencies. In order to control the wave propagation, 10 small aluminium cylinders, 7 mm thick, 1 cm high are attached to the metal. Between the sheet and the cylinders sit piezo discs. These discs can be stimulated electronically and change their thickness in a flash.
Using the piezo discs researcher were able to control exactly whether and how vibrations are allowed to propagate in the sheet-metal strip. One configuration of the discs enables a certain frequency spectrum of the waves to be absorbed. This muffling is variable as the piezo elements can alter their elastic properties electronically in fractions of a second – from low to high stiffness. The piezo controls can also be set so that waves are able to propagate through the sheet-metal strip “perfectly normally”, for example as though no aluminum cylinders were attached to it.
Andrea Bergamini from EMPA is supervisor of the project, which is called Phononic Crystal with Adaptive Connectivity. He said: “Imagine you produce a sheet of metal, imprinted with an electronic circuit and small piezo elements at regular intervals. This sheet metal could be programmed electronically to block a certain vibration frequency. The interesting thing is that even if you cut off part of the sheet, the waves in the cropped section would largely spread in the same way as in the initial piece.”
This method could be used on 3D components, he added. The development of a programmable material that can react and adapt to different vibrations would could “fundamentally revolutionise mechanical engineering and plant construction”, said the EMPA Research Institute.
Engineers determine vibration properties as much as possible currently by selecting material and geometry.
The researchers now plan to expand the programmability of the prototype. Bergamini said: “Until now, every piezo element has reacted to vibrations alone, independent of its neighbour. As the next step, we want to interconnect the elements with each other to be able to control them jointly or in a coordinated fashion.”