Scalable and High-Throughput Top-Down Manufacturing of Optical Metasurfaces

Metasurfaces have shown promising potential to miniaturize existing bulk optical components thanks to their extraordinary optical properties and ultra-thin, small, and lightweight footprints. However, the absence of proper manufacturing methods has been one of the main obstacles preventing the practical application of metasurfaces and commercialization. Although a variety of fabrication techniques have been used to produce optical metasurfaces, there are still no universal scalable and high-throughput manufacturing methods that meet the criteria for large-scale metasurfaces for device/product-level applications. The fundamentals and recent progress of the large area and high-throughput manufacturing methods are discussed with practical device applications. We systematically classify various top-down scalable patterning techniques for optical metasurfaces: firstly, optical and printing methods are categorized and then their conventional and unconventional (emerging/new) techniques are discussed in detail, respectively. In the end of each section, we also introduce the recent developments of metasurfaces realized by the corresponding fabrication methods.

Large-area hard magnetic L10-FePt nanopatterns by nanoimprint lithography

Large-area hard magnetic L1(0)-FePt nanopatterns with out-of-plane texture were fabricated by using a top-down approach. For the fabrication process, ultraviolet nanoimprint lithography (UV-NIL) in combination with inductively coupled plasma reactive Ar-ion etching was used. By this technique a continuous L1(0)-Fe(51)Pt(49) film was nanostructured into a regular arrangement of nanodots over an area of 4 mm(2). The dot dimension and distribution was specified by the stamp, resulting in a dot size of 60 nm and a periodicity of 150 nm. For the large-scale L1(0)-FePt nanopatterns, huge coercivities up to 4.31 T could be achieved. By means of magnetic force microscopy it could be verified that the nanodots were magnetically decoupled from each other and occurred in the single-domain state with perpendicular magnetization.

Flexible fabrication and applications of polymer nanochannels and nanoslits

Fluidic devices that employ nanoscale structures (<100 nm in one or two dimensions, slits or channels, respectively) are generating great interest due to the unique properties afforded by this size domain compared to their micro-scale counterparts. Examples of interesting nanoscale phenomena include the ability to preconcentrate ionic species at extremely high levels due to ion selective migration, unique molecular separation modalities, confined environments to allow biopolymer stretching and elongation and solid-phase bioreactions that are not constrained by mass transport artifacts. Indeed, many examples in the literature have demonstrated these unique opportunities, although predominately using glass, fused silica or silicon as the substrate material. Polymer microfluidics has established itself as an alternative to glass, fused silica, or silicon-based fluidic devices. The primary advantages arising from the use of polymers are the diverse fabrication protocols that can be used to produce the desired structures, the extensive array of physiochemical properties associated with different polymeric materials, and the simple and robust modification strategies that can be employed to alter the substrate's surface chemistry. However, while the strengths of polymer microfluidics is currently being realized, the evolution of polymer-based nanofluidics has only recently been reported. In this critical review, the opportunities afforded by polymer-based nanofluidics will be discussed using both elastomeric and thermoplastic materials. In particular, various fabrication modalities will be discussed along with the nanometre size domains that they can achieve for both elastomer and thermoplastic materials. Different polymer substrates that can be used for nanofluidics will be presented along with comparisons to inorganic nanodevices and the consequences of material differences on the fabrication and operation of nanofluidic devices (257 references).