Search

Self‐assembly processes provide the means to achieve scalable and versatile metamaterials by "bottom‐up" fabrication. Despite their enormous potential, especially as a platform for energy materials, self‐assembled metamaterials are often limited to single phase systems, and complex multi‐phase metamaterials have scarcely been explored. A new approach based on sequential self‐assembly (SSA) that enables the formation of a two‐phase metamaterial (TPM) composed of a disordered network metamaterial with embedded nanoparticles (NPs) is proposed. Taking advantage of both the high‐spatial and high‐energy resolution of electron energy loss spectroscopy (EELS), inhomogeneous localization of light in the network is observed, concurrent with dipolar and higher‐order localized surface plasmon modes in the nanoparticles. Moreover, it is demonstrated that the coupling strength deviates from the interaction of two classical dipoles when entering the strong coupling regime. The observed energy exchange between two phases in this complex metamaterial, realized solely through self‐assembly, implies the possibility to exploit these disordered systems for plasmon‐enhanced catalysis. [ABSTRACT FROM AUTHOR]

Hyperbolic metamaterials show exceptional optical properties, such as near‐perfect broadband absorption, due to their geometrically‐engineered optical anisotropy. Many of their proposed applications, such as thermophotovoltaics or radiative cooling, require high‐temperature stability. In this work, Ag/a‐Si multilayers are examined as a model system for the thermal stability of hyperbolic metamaterials. Using a combination of nanotomography, finite element simulations, and optical spectroscopy, the thermal and optical instability of the metamaterials is mapped. Although the thermal instability initiates at 300 °C, the hyperbolic dispersion persists up to 500 °C. Direct finite element simulations on tomographical data provide a route to decouple and evaluate interfacial and elastic strain energy contributions to the instability. Depending on stacking order the instability's driving force is either dominated by changes in anisotropic elastic strain energy due thermal expansion mismatch or by minimization of interfacial energy. These findings open new avenues to understand multilayer instability and pave the way to design hyperbolic metamaterials able to withstand high temperatures. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mechanical metamaterials showing tunable non-linear strain-stiffening • Strain-stiffening by deformation-induced transitions in nodal topology • Fundamental principle independent of loading conditions • Tunable mechanical response by unit cell geometry and combination of unit cells Mechanical metamaterials are periodic lattice structures with complex unit cell architectures that can achieve extraordinary mechanical properties beyond the capability of bulk materials. A class of metamaterials is proposed, whose mechanical properties rely on deformation-induced transitions in nodal-topology by formation of internal self-contact. The universal nature of the principle presented, is demonstrated for tension, compression, shear and torsion. In particular, it is shown that by frustration of soft deformation modes, large highly non-linear stiffening effects can be generated. The tunable non-linear modulus increase can be exploited to design materials mimicking the complex mechanical response of biological tissue. [ABSTRACT FROM AUTHOR]