Nanoimprint lithography (NIL) is a nonconventional lithographic technique for high‐throughput patterning of polymer nanostructures at great precision and at low costs. Unlike traditional lithographic approaches, which achieve pattern definition through the use of photons or electrons to modify the chemical and physical properties of the resist, NIL relies on direct mechanical deformation of the resist material and can therefore achieve resolutions beyond the limitations set by light diffraction or beam scattering that are encountered in conventional techniques. This Review covers the basic principles of nanoimprinting, with an emphasis on the requirements on materials for the imprinting mold, surface properties, and resist materials for successful and reliable nanostructure replication.

Colour and spectral imaging systems typically use fi lters and glass prisms to disperse light of different wavelengths. With the miniaturization of integrated devices, current research on imaging sensors focuses on novel designs aiming at high effi ciency, low power consumption and slim dimension, which poses great challenges to the traditional colourant-based fi ltering and prismbased spectral splitting techniques. In this context, surface plasmon-based nanostructures are attractive due to their small dimensions and the ability to effi ciently manipulate light. In this article we use selective conversion between free-space waves and spatially confi ned modes in plasmonic nanoresonators formed by subwavelength metal -insulator -metal stack arrays to show that the transmission spectra through such arrays can be well controlled by using simple design rules, and high-effi ciency colour fi lters capable of transmitting arbitrary colours can be achieved. These artifi cial nanostructures provide an approach for high spatial resolution colour fi ltering and spectral imaging with extremely compact device architectures.

Nanoimprint is an emerging lithographic technology that promises high-throughput patterning of nanostructures. Based on the mechanical embossing principle, nanoimprint technique can achieve pattern resolutions beyond the limitations set by the light diffractions or beam scatterings in other conventional techniques. This article reviews the basic principles of nanoimprint technology and some of the recent progress in this field. It also explores a few alternative approaches that are related to nanoimprint as well as additive approaches for patterning polymer structures. Nanoimprint technology can not only create resist patterns as in lithography but can also imprint functional device structures in polymers. This property is exploited in several non-traditional microelectronic applications in the areas of photonics and biotechnology.

The ability of micro-to nanometer-scale patterning on flexible substrates can enable many new applications in the area of photonics and organic electronics. A major roadblock has remained for many practical applications of patterned nanostructures, which is the throughput of nanopattern replication and the associated cost issues. Among the emerging techniques, nanoimprint lithography (NIL) clearly stands out as a promising technology for high-throughput and highresolution nanometer-scale patterning, [1,2] which can achieve resolutions beyond the limitations set by light diffraction or beam scattering that are encountered in other traditional techniques. Developments in this area have enjoyed great momentum in the past decade and numerous applications, such as in Si electronics, [3,4] organic electronics and photonics, [5,6] magnetics, [7,8] and biology [9][10][11][12] have been exploited by many researchers. On the other hand, the current process and throughput in NIL (on the order of a few minutes per wafer) is still far from meeting the demands of many practical applications, especially in photonics, biotechnology, and organic optoelectronics. The concept of roller imprinting has been pursued by previous investigators as a means to improve speed.[13] However, the procedure was to imprint a small piece of Si mold onto a Si substrate, which is not too different from that of conventional NIL except that a rod is used to apply pressure rather than a flat plate. The reverse nanoimprinting [14] or nanotransfer printing methods [15] produce positive-tone polymer or metal patterns, which in principle can also be applied to roll-to-roll printing processes. In addition, Lee et al. proposed a bilayer transfer process from a ''rigiflex'' mold to a Si wafer, [16] and pointed out that the process can potentially be extended to a roller bilayer transfer process. However, these are yet to be demonstrated.The motivation of this work is to enable continuous printing of nanostructures on a flexible web with drastically increased throughput, and thereby push the nanometer-scale lithography to an entirely new level. The roll-to-roll nanoimprint lithography (R2RNIL) technology presented in this Communication inherits its high-resolution feature from traditional NIL because it is also based on a mechanical embossing approach, but with a speed of nanopatterning increased by at least one or two orders of magnitude.The R2RNIL process primarily targets large-area patterning of nanostructures. In the conventional approach, embossing a large area requires a very large force. Huge contact areas between the mold surface and the imprinted nanostructures also produce significant adhesion force, making the mold-sample separation without damaging the substrates difficult or even impossible. In thermal NIL, if the mold and substrate are made from materials with different thermal expansion coefficients, such as Si mold and polymer substrate, stress can build up during a thermal cycle of such a magnitude that it can even destroy the Si mold during ...

Transparent metal electrodes fabricated by nanoimprint lithography show high optical transmittance as well as good electrical conductivity. Organic solar cells prepared using these transparent metal electrodes demonstrate an equal performance to those prepared with conventional ITO electrodes.