What are metamaterials? Why are they important to nanotechnology? There was a recent article in the IEEE Spectrum Magazine that addressed the customization of material structures [1]. Meta is from the Greek and means beyond or after. Metamaterials are materials that exhibit properties that are not found in nature. The current trend in metamaterials is the “invisibility cloaking” devices and wireless charging is a near term possible application [2]. There is an interesting depiction in the IEEE article showing what the effects of a negative index of refraction. A key is the ability to custom build the material structure to provide the desired effect.
A question that always arises – at least to me – is what are the properties of 100% pure elements? As we develop applications/products, there are specifications that we add to the purity of the materials being used, e.g., 99% or 99.9% pure material. Why do we specify the purity? We want to have a certain level of performance. If we have circuits that require high levels of conductivity, we may move from one material to another, e.g., aluminum to copper. There is always a trade-off. Higher levels of purity might improve performance, but higher levels of purity are more expensive. Consequently, switching to a higher conductivity material in semiconductors required developing a new process for depositing the copper. When the cost of developing a new process is amortized over billions of devices, the initial high cost is not that significant as compared to higher material costs.
We currently insert doping atoms into materials to change the properties of materials and create materials that permit the control of electron flow. Nature does the same thing. Diamonds, which are a form of carbon, are normally clear (white). However, if there are impurities in the carbon when the diamond was created the color can change to blue, yellow, or other colors.
There had been work, both theoretical and experimental, that has shown that some materials, silver and platinum, have a magnetic moment in 13 atom clusters. If we add the fact that arrangements of atoms can create nanomaterials and these nanomaterials can aggregate (group together) and not merge into a larger nanomaterial or into the bulk material, there are opportunities to develop interesting applications. This work has only started. The future looks very interesting.
[1] http://spectrum.ieee.org/semiconductors/materials/how-to-make-a-better-invisibility-cloakwith-lasers
[2] http://www.businessinsider.com/metamaterials-invisibility-cloak-2013-12
