topodefect[source]  Mechanical metamaterials denote an unconventional class of materials that offer an excellent platform to study various microscopic phenomena at the macroscopic level. Recently we designed and 3D-printed an anisotropic metamaterial, and by careful manipulation of only a small part of its elements, we could mimic topological defects that usually occur, e.g., in liquid crystals.

square[source]  Pushing and pulling on a material’s surface in a steady, periodic way is a common test for characterizing that material’s mechanical properties. Simple materials typically exhibit a single steady state response to a given way of forcing. We proposed a metamaterial made of mechanically bistable elements, which responds with a wide variety of distinct steady state cycles in response to just a single, persistently applied periodic force. This metamaterial could be a step towards building materials that exhibit dynamic forms of memory in their response to periodic driving.

Each unit cell in the metamaterial spontaneously adopts one of two minimum energy deformation modes. As a result, different regions within the material settle into one or the other stable mechanical phases, analogous to competing positive and negative domains in a ferromagnet. The boundary force pattern selects the preferred mechanical phase along a given portion of the boundary.

shear_ice[source]  Physical phenomena oftentimes exhibit distinct qualitative behavior in different dimensions. So, can one make a two-dimensional system behave as in three dimensions? We introduce a simple shear transformation in a two-dimensional artificial ice, and by that we recover some of the properties of natural three-dimensional ice. Three-dimensional water ice has multiple spatial configurations of its molecules that all possess the same energy, hence the system is degenerate and it always exhibits some disorder. Its two-dimensional counterpart, the square ice, lacks such a degeneracy. By combining experiments, theory, and numerical simulations, we constructed an artificial two-dimensional ice composed of micrometer-sized colloidal particles.

fiber_lattice[source]  The extracellular matrix (ECM) is a complex and highly dynamic fibrous environment that serves as the scaffold of cells in living tissues. The ECM is an anisotropic structure that is continuously remodeled by cells, which apply mechanical forces on the fibers to generate long-range inter-cellular interactions. We propose a mechanism for biochemical-mechanical signaling feedback based on the fact that as the ECM is remodeled, molecular transport is affected.








jamming290x290[source] Glass-forming liquids, granular systems, colloids, emulsions and foams exhibit a huge increase in relaxation time while their structure is hardly affected. From the analogy between the glass, or jamming, transition and other phase transitions, one would expect to find a growing correlation length governing the slow dynamics; however this length scale remains elusive. One of the leading suggestions for a relevant length scale comes from the heterogeneity of the dynamics.


traction290x290[source] The elastic cytoskeleton of biological cells contains molecular motors that produce mechanical forces by which cells attach to and pull on their surroundings. This mechanical interaction is responsible for many aspects of cellular function, from cell spreading and proliferation to stem-cell differentiation and tissue development. Both the cytoskeleton and the extracellular matrix comprise cross-linked, semi-flexible polymeric filaments, and as such they exhibit very nonlinear viscoelastic behavior that includes a power-law stiffening of the elastic moduli with increasing stress.



double network290x290



smallflo[source] We used molecular dynamics simulations to investigate energy distributions and spatial clustering in granular gases. Scaling arguments and mean-field calculations we performed for the granular temperature in these systems helped us gain insight on the nature of energy flow in more general driven dissipative systems. We then introduced a solvable stochastic model for dissipative interactions in generic systems, including granular materials, foams, colloidal suspensions and bacterial baths.