Harnessing plasticity in sequential metamaterials for ideal shock absorption.

Mechanical metamaterials exhibit interesting properties such as high stiffness at low density, enhanced energy absorption, shape morphing, sequential deformations, auxeticity and robust waveguiding. Until now, metamaterial design has primarily relied on geometry, and materials nonlinearities such as viscoelasticity, fracture and plasticity have been largely left out of the design rationale. In fact, plastic deformations have been traditionally seen as a failure mode and thereby carefully avoided.

Buckling Metamaterials for Extreme Vibration Damping.

Damping mechanical resonances is a formidable challenge in an increasing number of applications. Many passive damping methods rely on using low stiffness, complex mechanical structures or electrical systems, which render them unfeasible in many of these applications. Herein, a new method for passive vibration damping, by allowing buckling of the primary load path in mechanical metamaterials and lattice structures, is introduced, which sets an upper limit for vibration transmission: the transmitted acceleration saturates at a maximum value in both tension and compression, no matter what the input acceleration is.

Enhancing foci on breast MRI: Identifying criteria that increase levels of suspicion.

Objective: Prior studies evaluating features of foci associated with malignancy have not been conclusive. This study evaluates foci that were deemed suspicious and assesses multiple imaging and clinical findings with the goal of identifying criteria that can increase diagnostic confidence when evaluating foci on breast MRI.

Methods: After Institutional Review Board approval, a retrospective chart review was performed to identify patients who underwent an image-guided biopsy of an enhancing focus.

Inverted and Programmable Poynting Effects in Metamaterials.

The Poynting effect generically manifests itself as the extension of the material in the direction perpendicular to an applied shear deformation (torsion) and is a material parameter hard to design. Unlike isotropic solids, in designed structures, peculiar couplings between shear and normal deformations can be achieved and exploited for practical applications. Here, a metamaterial is engineered that can be programmed to contract or extend under torsion and undergo nonlinear twist under compression.

Oligomodal metamaterials with multifunctional mechanics.

Mechanical metamaterials are artificial composites that exhibit a wide range of advanced functionalities such as negative Poisson's ratio, shape shifting, topological protection, multistability, extreme strength-to-density ratio, and enhanced energy dissipation. In particular, flexible metamaterials often harness zero-energy deformation modes. To date, such flexible metamaterials have a single property, for example, a single shape change, or are pluripotent, that is, they can have many different responses, but typically require complex actuation protocols.