Preface

The term Lithography encompasses a range of contemporary technologies for micro and nano scale fabrication. Originally driven by evolution of the semiconductor industry, lithography has grown from its optical origins to demonstrate increasingly fine resolution and to permeate many diverse research fields. Today, greater flexibility and affordability is demanded from lithography than ever before. Diverse needs across many disciplines have produced a multitude of innovative new lithography techniques. This book provides an overview of some of the varied approaches and applications of lithography today.

Nano-imprint lithography is regarded a one of the most competitive alternative fabrication technologies available today. It offers exceptional resolution, high throughput and simple execution at very low cost. The first section of this book, by Barbillon, provides an introduction to nano-imprinting by describing the fabrication of nano-structures for plasmonic biosensing.

Soft lithographies, derived from nano-imprint technologies, operate at largely ambient environmental conditions. This makes them inherently compatible with delicate biological materials such as proteins. Section 2 describes the application of soft lithography in the context of neurobiology. The work by Kan et al. investigates techniques for directing the growth of neurons, with the intention of creating complex neural networks of specific geometry. Similarly, Takayama et al. explore techniques for controlling the differentiation of stem cells.

Self-assembly techniques are often employed for their capacity to pattern large substrate areas with nanoscale resolution at a very low cost. Colloids are a well established platform in the self-assembly arena, and have been applied in areas as diverse as photonic crystals and nanoscale plasmonics. In Section 3, sub-micron colloidal particles are employed as nonplanar substrates for the controlled deposition of a second tier of self-assembled nano-structures. Nonckreman et al. pursue this objective by demonstrating the controlled deposition of nano-sized colloids on top of sub-micron colloids, while Li et al. investigate the self-assembled nano-structuring of thin films as they are deposited on top of close-packed colloids.

Diffractive optical elements typically require fabrication of periodic sub-wavelength elements. For the visible spectrum, this typically translates to sub-micron and

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nanoscale dimensions. In Section 4, Wen et al. investigate the design and fabrication of circular Dammann diffractive gratings, while Motogaito et al. demonstrate binary diffractive lenses via electron beam lithography. Finally, Fragouli et al. bring this section to a close by demonstrating very interesting work with photochromic polymers. These are imprinted with grating structures, and then shown to be capable of reversible dimensional changes when illuminated with specific wavelengths. Their application to tuneable wetting and tuneable diffraction is also demonstrated.

Section 5 concludes this book by describing some of the challenges faced by the next generation optical lithography technique. Here, shorter wavelengths, in the extreme ultraviolet regime, are harnessed to enable enhanced nanoscale fabrication.

This book represents the collective efforts and creative talents of many researchers worldwide. On behalf of these authors, and the staff at InTech publishing, I hope that you find these collected works informative, and a pleasure to read.

> **Gorgi Kostovski** *RMIT University Australia*
