Direct-write techniques enable computer-controlled two- and three-dimensional pattern formation in a serial fashion. Among these techniques, the versatility offered by laser-based direct-write methods is unique, given their ability to add, remove, and modify different types of materials without physical contact between a tool or nozzle and the material of interest. Laser pulses used to generate the patterns can be manipulated to control the composition, structure, and even properties of individual three-dimensional volumes of materials across length scales spanning six orders of magnitude, from nanometers to millimeters. Such resolution, combined with the ability to process complex or delicate material systems, enables laser direct-write tools to fabricate structures that are not possible to generate using other serial or parallel fabrication techniques. The goal of the articles in this issue of MRS Bulletin is to illustrate the range of materials processing capabilities, fundamental research opportunities, and commercially viable applications that can be achieved using recently developed laser direct-write techniques. We hope that the articles provide the reader with a fresh perspective on the challenges and opportunities that these powerful techniques offer for the fabrication of novel devices and structures.

This article summarizes research on laser-based processing and structuring of materials at the nanoscale using optical near-field schemes. Both apertureless and tapered fiber near-field scanning optical microscope probes can deliver highly confined irradiation at sufficiently high intensities to cause morphological and structural changes in materials at the nanometer level. The energy emitted by the probes and the absorption within the target material are predicted by carrying out calculations of the near-field electromagnetic distribution. The effects of shrinking laser beam dimensions compete with the energy diffusion into the target material. Experimental results have shown well-controlled subtractive material modification with minimum feature size in the neighborhood of 10 nm. Precise patterning can be achieved via laser-assisted chemical etching. Control of the nucleation of nanostructures via rapid melting and crystallization is demonstrated. The article concludes with an outlook to applications.

This article reviews recent developments in laser direct-write addition (LDW+) processes for printing complex materials. Various applications, ranging from small-scale energy storage and generation devices to tissue engineering, require the ability to deposit precise patterns of multicomponent and multiphase materials without degrading desirable properties such as porosity, homogeneity, or biological activity. Structurally complex inorganic materials for the successful fabrication of alkaline and lithium-based microbatteries, micro-ultracapacitors, and dye-sensitized micro solar cells are shown on various low-processing-temperature and flexible substrates using LDW+. In particular, the ability to deposit thick layers while maintaining pattern integrity allows devices produced in this manner to exhibit higher energy densities per unit area than can be achieved by traditional thin-film techniques. We then focus on more complex systems of living and biologically active materials. Patterns of biomaterials such as proteins, DNA, and even living cells can be printed using LDW+ with high spatial and volumetric resolution on the order of a picoliter or less, without compromising the viability of these delicate structures. These results provide for highly selective sensor arrays or cell seeding for tissue engineering. Finally, we review recent work on LDW+ of entire semiconductor circuits, showing the broad range of applications this technique enables.

Three-dimensional structures of selected materials can be written directly to the precise locations required using laser exposure of suitable gaseous precursor mixtures. Writing speeds exceeding 50 μm/s can be achieved. Examples presented in this work include the creation of a tiny time-of-flight laser ionization mass spectrometer, laserdriven movable micro-objects, and an ac electric-field microcage for storage, handling, and transferring small neutral objects in aqueous solution. The impact for lasercontrolled site-selective growth of carbon nanotube cables is demonstrated.

Current technology trends imply that further miniaturization and integration of systems are anticipated, and one approach to realizing the next generation of systems integration is the development of materials that are protean, or capable of taking on various properties; in essence, the materials properties can be selectively altered via laser excitation. The objective is that a common substrate material can be used for multiple functions. Laser direct-write material processing, because of its maskless patterning flexibility, is inherently suitable for producing localized changes in materials properties and thereby fabricating linked, integrated devices on a common substrate. The enabling of this new form of materials processing requires a light-activated protean material along with a scheme for the dynamic regulation of the laser energy for optimum laser processing on the scale of the laser spot size and for patterning speeds on the order of meters per second. The “protean material” concept and a high-fidelity laser amplitude-modulation scheme are the focus of this article.

Laser direct-write (LDW) is an established technology for manufacturing electronic and optoelectronic appliances such as cellular telephones, digital cameras, and notebook-type personal computers. One of the most successful applications is laser drilling of via holes on printed circuit boards for the manufacture of cellular telephones. Other practical applications include marking, dicing, trimming, repairing, patterning, bending, and rapid prototyping. In this article, the state of the art of LDW for industrial applications in Japan, the United States, and Europe is reviewed, and its future prospects are discussed.

This article is based on the presentation given by Max G. Lagally (University of Wisconsin–Madison) as part of Symposium X: Frontiers of Materials Research on April 18, 2006, at the Materials Research Society Spring Meeting in San Francisco.

Structures with nanoscale dimensions are the essence of nanotechnology. Beginning with quantum dots and buckyballs, nanostructures now include nanotubes, rods, wires, and most recently, nanomembranes: very thin, large, freestanding or freefloating strain-engineered single crystals that can variously be made into tubes or other shapes, cut into millions of identical wires, or used as conformal sheets. This article provides a brief overview of the fabrication and properties of strained-silicon nanomembranes.