Over the last two decades, our ability to create networks of fluidic channels of submillimeter or even sub-micrometer diameters has led to a wide range of microchemical applications. Whereas early efforts were directed toward the development of microanalysis systems, in more recent times the development of microreactors and tools for biotechnology and basic biological studies has emerged. This issue of MRS Bulletin highlights the many different ways in which material properties are crucial in the fabrication, assembly, and operation of micro- and nanofluidic systems. Choice-of-material considerations range from an assessment of whether a desired channel design can be microfabricated in a certain material to whether the material is compatible with the operating conditions (i.e., pressure, temperature) and the chemical composition (solvent, solutes) of the fluid used. Moreover, in certain cases, specific surface or bulk material properties can be used to the benefit of the application of the device. In the development of today's wide range of integrated micro- and nanofluidic applications, a common challenge emerges: meeting the often contradictory set of constraints imposed on the physical and chemical properties of materials by the envisioned applications. This issue reviews these challenges and their solutions and provides an outlook on how the ingenious use of existing and new materials can spur the development of ever more sophisticated micro- and nanofluidic systems.

This article is based on the plenary address given by George M. Whitesides of Harvard University on March 30, 2005, at the Materials Research Society Spring Meeting in San Francisco. Materials science and biomedicine are arguably two of the most exciting fields in science today. Research at the border between them will inevitably be a major focus, and the applications of materials science to problems in biomedicine—that is, biomaterials science—will bud into an important new branch of materials science. Accelerating the growth of this area requires an understanding of two very different fields, and being both thoughtful and entrepreneurial in considering “Why?” “How?” and “Where?” to put them together. In this fusion, biomedicine will, we believe, set the agenda; materials science will follow, and materials scientists must learn biology to be effective.

Nanoimprint lithography is a potentially low-cost, high-resolution patterning technique, but most of the surrounding development work has been directed toward tool designs and processing techniques. There remains a tremendous opportunity and need to develop new materials for specific nanoimprint applications. This article provides an overview of relevant materials-related development work for nanoimprint lithographic applications. Material requirements for nanoimprint patterning for the sub-45-nm integrated-circuit regime are discussed, along with proposed nanoimprint applications such as imprintable dielectrics, conducting polymers, biocompatible materials, and materials for microfluidic devices. Polymers available for thermal nanoimprint processing and photocurable precursors for ultraviolet-assisted nanoimprint lithography are discussed.