3D optical metamaterial by self-assembly

Polymer self-assembly into structurally chiral structures give rise to optical metamaterials

Block copolymer (BCP) self-assembly is a unique route to creating macroscopically large samples with a complex fully three dimensional architecture with features on the nanometer length scale.

The individual blocks of the BCP are chemically distinct and can be etched separately. This results in a porous scaffold that can be backfilled with metals in order to create novel materials with interesting optical properties. Such replication is possible because the blocks in BCPs are continuous, meaning that the pores will be interconnected. This is a very elegant way  to replicate self-assembled structures into materials that are not amenable to direct self-assembly in such complex morphologies.

In particular, we work with the gyroid morphology that exhibits strongly anisotropic plasmon modes with linear dichroism and optical chirality across the visible region.


Gyroid gold


Fabrication process:

We start with an isoprene-block-styrene-block-ethylene oxide (ISO) BCP that forms two chemically distinct, interpenetrating gyroid networks (I,O) of opposite chirality in a matrix of the third block. The I gyroid network is then removed by selective UV and chemical etching and back-filled with gold by electrodeposition. The final structure is a continuous, triply periodic network of gold. The dimension of the full unit cell is ≈50 nm, which is far below optical wavelengths. This particular morphology has been chosen since it is predicted to offer a strong resonant response that depends on the relative orientation between the structure and the polarization of the incident light.


Gyroid manufacture

Adolphe Merkle Institute - Chemin des Verdiers 4 - CH-1700 Fribourg - Phone +41 26 300 9254