**7. Perspective for the NSL in the controlled fabrication of nanomaterials**

The great progress in controlled synthesis/fabrication of noble metal NPs by NSL, and the increase in the experimental and theoretical achievements in control of their size, shape, surface morphology and 3-dimensional space orientation dependent physicochemical properties and functions suggest expanding application in many fields because of the potential for essential breakthroughs by researchers and engineers for more advanced applications of NSL. Particularly, the developed multi-step angle resolved NSL and the modified NSL incorporated with suitable post-treatments have enabled us to obtain uniform surface-confined overlapped and nano-gapped nanostructures, the tip-rounded triangular nanoprisms, the square-shaped and the trapezoidal nanoprisms, besides the common triangular nanoprisms. Besides the marvelous progresses in the surface-confined nanostructures fabrication, a modified NSL process has also been developed to dislodge these uniform nanomaterials into the desired solvents (e.g. water, ethanol) without any obvious agglomeration as in the solution-phased nanocolloids synthesis.

Progresses in the incorporation of NSL with other LIGA techniques have shown that the suitability and ability in the architecture and interspacing controlled fabrication of NPs and nanoarrays. Their applications can thus be expanded extremely. When the multi-hierarchy arrayed micro windows fabricated by the traditional UV-LIGA process is joined in NSL, one powerful method for single nanoparticle identification will be born, resulting in the possibility of the precise investigation of the 3D morphology dependent LSPR of nanoparticles and LSPR coupling in nanoarrays. By collaboration with UV-LIGA microfabrication, uniform noble metal nanoparticles or nanoarrays can be fabricated into the targeted micro channels, leading to a much sensitive optical biosensing system after their surfaces are modified by the traditional functionalization process. By combination of PAA-LIGA and NSL, the possibility for building hierarchically ordered multi-segment nanowires or nanorods will be realized conveniently.

Summarizing from the recent progresses and discussion on NSL presented in this chapter, four main researches thrust that includes several active and challenging topics may form the primary research focuses and directions in this particular field. One is the fabrication technique development for the formation of monolayer of nanospheres with uniform area as large as several centimeter squares, which founds the basis of NSL. Another is the convenient and practical process in the releasing of these surface confined nanomaterials into solvent with perfectly retained 3D morphologies, which is still challenging but a desired alternative to obtain the uniform nanomateirals besides the well-developed wet chemical process. The third is the advanced incorporation of NSL with other fabrication techniques besides LIGA processes for the building more complex 3D hierarchically ordered nanostructures, which will definitely make a breakthrough in the nanoscale device and assemble development. The fourth may be the fabrication of tunable hetero-structurecomposition nanocomposites, such as sandwich discs or multi-layer nanostructures, which will produce hetero-nanostructures with multi-functions (e.g. magntic, optical, electronic, etc). Consequently, outcomes of these challenging researches will result in the discovery of many exciting and versatile techniques for nanomaterials fabrication, and theoretical breakthrough in their novel physicochemical properties and for advanced applications.
