College of Science & Engineering
Mechanical metamaterials are man-made materials consisting of peculiar spatial arrangements of unit blocks, whose properties are superior to those exhibited by conventional materials and superior to those displayed by their individual components. Recent efforts in the applied physics community have been directed towards the development of techniques to provide metamaterials with tunable characteristics, i.e. the ability to modify their behavior in response to changes in certain externally controlled parameters or in the operational conditions. Popular avenues for tunability include methods involving electroelastic or magnetoelastic materials, thermoelastic effects, and buckling-induced lattice reconfigurations.
This group has recently explored two distinct strategies. The first is based on the correction of the mechanical properties of internal elements of metamaterials by means of piezoelectric phases. A recent extension of this paradigm involves the use of dielectric elastomers (such as electroactive polymers) which can undergo finite macroscopic deformation upon the application of voltage stimuli. They are currently in the process of simulating wave events excited in soft matamaterials undergoing drastic internal shape reconfiguration. The objective is to show that these changes in shape can result in non-negligible modifications of the spatial wave patterns induce in the material.
A second avenue towards tunability is based on the use of nonlinearity as a mechanism for wave control. Recently these researchers have introduced an approach to use the nonlinearity (material and geometric) of the medium to stretch the response of materials and distribute it intelligently over multiple wave modes, thus activating functionalities that are not achievable (in the same frequency ranges) in the corresponding linear cases. In this context, they are now performing simulations of nonlinear waves in a variety of media exhibiting nonlinear characteristics, including granular crystals, soft materials, and lattice materials with curved microstructural elements.
In addition to their efforts on tunability, the researchers are currently in the process of studying topological metamaterials, i.e., metamaterials featuring unconventional wave phenomena controlled by the topological structure of their band diagram. An example is the study of topological kagome lattices that exhibit asymmetric wave transport behavior and that can behave like mechanical diodes.