Mechanical metamaterials are a class of structured materials designed with a wide range of optimized responses to external forces, such as improved strength, enhanced vibrational dampening, thermal efficiency, energy absorption, and more. They’re created by embedding geometric patterns into common base materials, without chemical or molecular modifications. The base material is often metallic, elastomeric, or composite.
The metamaterial’s overall geometric design, unit (or “motif”) size, and orientation is generated and optimized computationally using kinematic analysis of mechanisms, homogenization theory, and full solid characterization. Optimized geometries are then embedded into a base material using 3D printing or other pattern transfer methods. The resulting physical properties are largely determined by the metamaterial’s geometric pattern. In short, metamaterials allow us to engineer materials with properties not found in naturally occurring materials (see: Wikipedia article on metamaterials).
Limitations and trade-offs in currently available materials impact manufacturing and construction. Making new materials is hard, expensive, and slow, so we need a new way for producing better materials.
Since new geometries – not new molecules – are being created, the time and costs to demonstrate a performance improvement are much lower with metamaterials. These geometries are also compatible with traditional manufacturing methods including injection molding, thermoforming, casting, milling, and roll-to-roll pattern transfer, which allows for easy mass production and simplification of the supply chain logistics. Where appropriate, we work with 3rd party contract manufacturers to achieve QA/QC, scale, and cost-savings that are passed on to our customers.
A motif is a single “unit cell” of a metamaterial. Metamaterial products are created by multiplying motifs to create larger sections, often in the form of blocks or panels. A final product may contain a single motif or combine several motifs, depending on the desired optimizations. MetaCORE and MetaTHERM are single motif metamaterials that can be tessellated into larger sections, while MetaCORE-LD is MetaCORE in a sandwich panel form.
The properties of a metamaterial motif – such as geometry, orientation, and unit size – all contribute to that metamaterial’s optimization. For example, MetaCORE offers a high impact absorption, large R-values, and is isotropic (provides optimized functionality all directions). Changing a property of a motif can change the resulting optimizations, making custom multi-objective optimizations possible.
Multiscale Systems was created with the intent to commercialize advanced materials research conducted by founders Jesse Silverberg, PhD, and Arthur Evans, PhD, during their doctoral and postdoctoral training.
Their primary motivation was to see their research on mechanical metamaterials progress beyond academic papers and into real-world applications. This motivation was enhanced by an apparent absence in the technical expertise required for the technology to be advanced by existing materials science/engineering firms, which are generally more focused on developing new chemical and molecular structures.
We design our metamaterials computationally using a combination of proprietary and professional engineering software, drawing on the original research of Jesse and Arthur, being one of the first companies to offer mechanical metamaterials to clients.
Mechanical materials can be made of a huge range of materials including metals, composites, elastomers, and plastics. The geometries that give mechanical metamaterials their optimized responses are largely agnostic to the material type, and can be applied across a range of conventional materials.
While they are both classed as metamaterials, mechanical and optical metamaterials differ in their responses to external forces. Optical metamaterials are a type of electromagnetic metamaterial that can affect electromagnetic waves. Mechanical metamaterials are classed as a type of structural metamaterial, which are more concerned with physical properties like density, strength, and stiffness. Mechanical metamaterials can take the functionality of structural metamaterials further by using corrosion-resistant or high-temperature materials, for example.
Probably the most commonly known example of a structured metamaterial is honeycomb. Honeycomb for structural applications was patented in 1914, and the following year Hugo Junkers used metal honeycomb cores for the first time in aircraft. By 1969, Boeing had incorporated fire-resistant honeycombs from Hexcel into their 747s. Cardboard honeycomb is widely used in packaging material (think corrugated cardboard boxes).
“Bespoke” is a popular buzzword these days, but that’s exactly what we offer our clients. The beauty of Multiscale System’s approach to metamaterial design and manufacturing is that it can be highly customized to suit a particular application. The motif geometry (or multiple geometries), material, density, cell size, etc. all affect the performance optimization of a finished metamaterial product. We work directly with our customers to develop a product that will deliver the exact requirements for their specific need.
Metamaterials can be created using a range of methods, including injection molding, thermoforming, casting, milling, roll-to-roll pattern transfer, as well as additive manufacturing (3D printing).
Yes, additive manufacturing – or 3D printing – is a viable method to produce the necessary metamaterial geometry. It also offers a number of advantages over traditional approaches:
- Metamaterial parts can be manufactured at the point and time of need, reducing reliance on supply chain logistics.
- 3D printing allows for relatively low-cost manufacturing, with the costs of materials and equipment becoming increasingly more affordable.
- Designs for 3D printed products can easily be improved and upgraded for new materials, making them future proof.
- By additively manufacturing metamaterials, designs can quickly be iterated, tested, and validated, making for quicker development cycles.
Technical data can be found in Resources, including datasheets, brochures, and white papers.
We have developed metamaterials for defense, aerospace, transportation, and energy. Often, metamaterials designed for one application can be used across several different markets. An example is MetaCORE, which can be used in impact absorbing defense applications, as well as improving crashworthiness in electric vehicles.
CFE is a ratio of stresses that measure how much force travels through an impact protecting material. This number is used in aerospace and automotive industries as way of determining the risk of head and neck injuries during a collision, but it can also be used to see how much force would be transmitted to cargo or other supplies. CFE is inversely related to the size of the peak on a stress-strain graph – larger peaks reduce the CFE to 0, offering the least amount of protection, while smaller peaks increase the CFE to its maximum value of 1, offering the most amount of protection:
The SEA is the total area under the flat part of the load-compression curve on the stress-strain graph, divided by the mass of the material that’s become crushed. A large SEA (> 20 kJ/kg) means lots of energy has been absorbed by the material on impact or that the material absorbing the impact is very lightweight. Many lightweight, high SEA materials – like honeycomb – are functional in only one direction, meaning they have low SEA and poor impact protection abilities in the other two directions. Off-axis impacts are generally not effectively dissipated with these materials. In comparison, MetaCORE was designed to be a pro-isotropic, high SEA metamaterial, which overcomes the uncertainty of knowing the impacting direction.
Honeycomb, commonly manufactured from plastic, metal, or fibrous pulp, is a type of metamaterial that is often used where impact protection is required. It has a strong Specific Energy Absorption in one direction, and none in the other two. MetaCORE has a strong SEA in all directions, which makes it isotropic and able to absorb energy from any direction. With Crush Force Efficiency, honeycomb has a large peak stress, whereas MetaCORE was designed to eliminate this problem and has virtually no peak stress.
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We’ve previously received several SBIRs from the U.S. Department of Energy, the National Science Foundation, and NASA. We’ve also received various awards and resources from the U.S. Department of Defense, accelerators, local organizations, and partner companies. See a full list of our funders and partners on our Impact page.