Nanotransfer printing based 3D NIM fabrication scheme. Schematics
showing complete steps from stamp fabrication, multi-layer growth to transfer
Nature Nanotechnology – Large-area flexible 3D optical negative index metamaterial formed by nanotransfer printing This nanotransfer process should be able to be used to produce sheets of new metamaterials of almost any size given the right resources, and what’s more should be able to do so in a reasonably economical manner, as the stamps are reusable. More research will still be needed however, before commercial products begin to appear because methods to create just the right kinds of stamps still need to be developed.
We report a simple printing approach capable of forming large-area, high-quality NIMs with three-dimensional, multilayer formats. Here, a silicon wafer with deep, nanoscale patterns of surface relief serves as a reusable stamp. Blanket deposition of alternating layers of silver and magnesium fluoride onto such a stamp represents a process for ‘inking’ it with thick, multilayer assemblies. Transfer printing this ink material onto rigid or flexible substrates completes the fabrication in a high-throughput manner. Experimental measurements and simulation results show that macroscale, three-dimensional NIMs (over 75 square centimeters) nano-manufactured in this way exhibit a strong, negative index of refraction in the near-infrared spectral range, with excellent figures of merit.
Previously we emphasized how this process can make invisibility practical. However, the metamaterials need not be ones that are suited for invisibility. The metamaterials could have patterns that are useful for other purposes.
Transfer of multi-layer stack to a target substrate. Steps showing release of multi-layer stack from the stamp to the target substrate.
Free standing 3D NIM. The picked up free standing 3D NIM where a mild adhesive surface (scotch tape) was used to pick up the free standing 3D stack.