Although artificially created metamaterials probably won't reach large-scale commercialization for 10 years or so, some are already appearing in niche applications like electronics, communications, and defense, says a new report from Lux Research, "Breaking the Rules: Emerging Metamaterials Drive Performance in New Directions." How quickly they become mainstream will depend largely on finding and developing cost-effective manufacturing methods, which will include additive manufacturing.
Metamaterials don't exist in nature. Their unusual properties are engineered to make materials with specific novel electromagnetic, acoustic, or mechanical characteristics using carefully designed and controlled nanostructures or microstructures. For example, we recently told you about a new materials class developed by Lawrence Livermore National Laboratory (LLNL) with unusual mechanical characteristics. They are super-lightweight, extremely stiff, and very high-strength, with the same weight and density as aerogels, but about 10,000 times the stiffness.
Metamaterials don't exist in nature. Their unusual properties are engineered to make materials with specific novel electromagnetic, acoustic, or mechanical characteristics using carefully designed and controlled nanostructures or microstructures.
(Source: Lux Research)
The unusual properties of metamaterials are demonstrated by the LLNL micro-architected materials that were developed with hugely improved mechanical properties. They maintain a nearly constant high stiffness per unit of mass density, which doesn't change when the constituent material changes, whether it's a metal, a ceramic, or a polymer. They also maintain those properties over three orders of magnitude and can withstand a load of at least 160,000 times their weight. These qualities are expected to be a big advantage in aerospace.
Other application examples given in the Lux report are electromagnetic metamaterials that enable invisibility cloaks, which entirely redirect electromagnetic radiation around an object. More mundane uses include superlenses that can produce extremely high-resolution images for better security scanners. Radio-frequency and microwave-frequency electromagnetic metamaterials have been created for antennas, waveguides, and filters that improve communications. Some acoustic metamaterials manipulate sound or vibration to create high-resolution ultrasound images, or redirect seismic waves around structures. Mechanical metamaterials are being developed with surfaces that can repel bacteria.
The most advanced metamaterials being produced today in government and academic research labs depend on expensive production processes such as photolithography, but implementing these technologies will depend on the development of cost-effective manufacturing methods that allow fine patterning, Anthony Vicari, Lux research associate and the report's lead author, tells Design News. "Some single-layer or few-layer electromagnetic metamaterials can be, and are, made using photolithography, or, for long wavelengths, electronics printing methods such as inkjet and screen printing," he says. "But mechanical and acoustic metamaterials, which rely on complex internal 3D structures, are best made additively. There are also groups working on self-assembly and on biological production methods, but I do not expect those to be as common." Additive processes are likely to be very important for all three classes.
Four different types of additive manufacturing processes are being developed for creating metamaterials at LLNL. The LLNL team co-developed its new materials with a team at MIT using an additive micro-manufacturing technique called projection micro-stereolithography. Metamaterials being engineered with these methods will have different combinations of mechanical and thermal properties, such as strength, density, and thermal expansion.