A method was developed that unifies the construction of varying types of mechanical metamaterials using a discrete lattice, or LEGO-like system, enabling the design of modular materials with properties tailored to their application. These building blocks and their resulting materials could lead to dynamic structures that can reconfigure on their own; for example, a swarm of robots could form a bridge to allow troops to cross a river. This capability would enhance military maneuverability and survivability of warfighters and equipment.

Motivated in part by swarms of tiny robots that link together to form any imaginable structure, these metamaterials may also enable future high-performance robotics and impact/blast-absorbing structures. Researchers started out trying to build a bridge made of robots but the work has since evolved into mobile robots made of robots.

The system relies on mass-produced, modular parts that are discretely assembled to form larger, functional mechanical metamaterials with novel properties. (Benjamin Jenett, MIT Center for Bits & Atoms)

Robots rearranging to form a bridge made of robots, similar to ants, is one embodiment of the concept of structural robotics, which blur the line between active and passive elements and feature reconfigurability. The system could enable the Army to build a variety of robots with unique properties like impact energy absorption. The researchers designed and demonstrated a range of useful properties including extreme stiffness, toughness, and unique couplings between displacement and rotation.

The system, based on cost-effective injection molding and discrete lattice connections, enables rapid assembly of macroscale structures that may combine characteristics of any of the four base material types: stiff; compliant; auxetic (materials that when stretched become thicker perpendicular to the applied force); and chiral (materials that are asymmetric in such a way that the structure and its mirror image cannot be easily viewed when superimposed). The resulting macro-architected materials can be used to build at scales orders of magnitude larger than achievable with traditional metamaterial manufacturing at a fraction of the cost.

The next phases of the research will explore the design space created by the system with target applications including modular soft robotics, impact-absorbing structures, and rapid construction at the point of demand. The researchers also want to investigate how traditional additively manufactured metamaterials might be integrated with this system to create large-scale hierarchical metamaterials, combining strengths across scales.

For more information, contact the U.S. Army CCDC Army Research Laboratory Public Affairs at 703-693-6477.