Mechanical Metamaterials: Cutting-Edge Metastructures

Mechanical metamaterials are artificially designed material systems with exotic properties rarely found in nature. The exciting features of mechanical metamaterials are usually defined by their geometric architecture and microarchitecture connectivity rather than composition. One can customize physical properties with exceptional or even opposite values than those found in natural materials. The earlier studies focused on exploring counter-intuitive physical properties such as negative Poisson's ratio, negative thermal expansion, negative stiffness, and negative compressibility. Boosted by advancements in additive manufacturing technologies, the research community have aggressively explored highly complex geometries yet exciting physical proper-ties, e.g., intricate 2D lattices, 3D lattices, granular structures, Origami, Kirigami, and tensegrities, which are applicable for energy storage, biomedical, thermoelastic polarization, acoustics, pho-tonics, and thermal management.

Recently, supported by advanced manufacturing such as 4D printing, active metamaterials have demonstrated excellent functionalities and tunable properties due to their adaptable capability to change shape in a programmable, untethered, and reversible manner, showing potential applications in soft robots, actuators, shape morphing structures, intelligent biomedical devices, thermal engineering devices, tunable physical properties, elastic wave control, and acoustics. Combining structural mechanics and functional materials, one can reconfigure structures mainly controllable by heat, fluid, light, magnetic field, external force, and other external stimuli.

This research topic aims to disseminate novel research findings in mechanical metamaterials.

We invite two paper types – i) original research or ii) review, on the fundamental studies on mechanical metamaterials' mechanics and design and their engineering applications across various scales. Examples of topics include (but are not limited to):

• Metamaterials with negative Poisson's ratio, negative thermal expansion, negative stiff-ness, negative compressibility, and other tunable properties
• Analytical, numerical, and experimental studies on the behaviors of architected structures, lattice materials, foams, granular structures, origami, kirigami, and tensegrities
• Mechanics and design of reconfigurability, tunability, multi-stability, symmetry breaking, coupling effects, and other interesting functional properties of mechanical metamaterials
• Advanced technologies such as 3D/4D printing to manufacture mechanical metamaterials.
• Active metamaterials deformable by external stimuli.

Keywords: Mechanical metamaterials, Architected Materials, Active metamaterials, Metastructures, Mechanics and Design

Important note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.