Synopsis: Geometrical Frustration Takes a Stretch

A large-scale triangular lattice made of elastic elements reveals how geometrical frustration can result in complex, but ordered, patterns.
Synopsis figure
S. H. Kang et al., Phys. Rev. Lett. (2014)

Geometrical frustration occurs when a system of interacting particles is unable to find its lowest energy state because of how the particles are arranged. This property plays an important role at microscopic scales in solids, and in particular, magnets, where the absence of a single, lowest-energy state can, for example, affect a material’s conductivity.

Katia Bertoldi and her colleagues at Harvard University have now investigated geometrical frustration on a macroscopic scale. The researchers designed a lattice of triangular tiles with sides made from 5-millimeter-long silicone rubber beams. The lattices were prepared such that the angle between the beams at each vertex, or “joint,” was the same and each joint experienced the same mechanical stress. Frustration resulted when the researchers compressed the lattice, since there was no way for all of the beams to simultaneously buckle and still preserve equal angles at each joint.

Bertoldi and her colleagues observed that the ratio of the thickness of the beams to their length—the material’s porosity—controlled the geometry of the lattice as they applied an equal compressive force along the lattice’s perimeter. As reported in Physical Review Letters, the team found that highly porous structures preferentially formed ordered chiral patterns when compressed, while denser structures tended to exhibit ordered symmetrical patterns. The appearance of complex, ordered patterns is surprising, given that previous studies of frustrated systems show that they tend to be disordered. These results suggest that, contrary to what was previously thought, ordered structures can arise in frustrated systems without the addition of defects such as dopants. – Katherine Kornei


Features

More Features »

Announcements

More Announcements »

Subject Areas

MagnetismMaterials Science

Previous Synopsis

Next Synopsis

Related Articles

Synopsis: Golden Mystery Solved
Materials Science

Synopsis: Golden Mystery Solved

A long-standing discrepancy between experiments and theory concerning the electronic properties of gold has now been resolved. Read More »

Synopsis: Metamaterial Inverts the Hall Effect
Materials Science

Synopsis: Metamaterial Inverts the Hall Effect

A metamaterial that looks like chainmail has a Hall coefficient whose sign is flipped compared to the material it’s made from. Read More »

Focus: Why Some Gels Shrink under Stress
Mechanics

Focus: Why Some Gels Shrink under Stress

The gel material that helps blood clot in a wound has anomalous material properties because of the interaction between the gel's fluid and its microscopic fiber network, according to experiments. Read More »

More Articles