Conventional photolithography is an effective patterning technique that has enabled modern electronics and advanced micro- and nanoscale devices. However, it has limitations, including high cost, limited resolution, and poor compatibility with unconventional materials that may be soft, nonplanar, or difficult to process. There is active research ongoing to develop unconventional patterning methods such as self-organization and self-folding. Self-organization harnesses various driving forces to produce patterns without external intervention and includes methods such as self-assembly of block copolymers, capillary-driven assembly of micro-/nanoscale structures, and thin-film instabilities. Self-folding (origami)—and its cousin, kirigami—harnesses patterning and materials strategies to convert planar substrates into three-dimensional shapes in response to external stimuli. These multidisciplinary approaches open many engineering opportunities by providing new and versatile material functionalities. This article overviews the field and the topics covered in the articles in this issue of MRS Bulletin, highlighting recent progress in patterning approaches based on self-organization and self-folding.

Block copolymers (BCPs) microphase-separate to form periodic patterns with periods of a few nanometers and above without the need for lithographic guidance. These self-assembled nanostructures have a variety of bulk geometries, including alternating lamellae, gyroids, arrays of cylinders or spheres, tiling patterns and core–shell structures, depending on the molecular architecture of the polymer and the volume fraction of its blocks. Non-bulk morphologies can be produced, the ordering of the microdomains can be improved, and their locations can be directed using various templates and processing strategies. The blocks themselves can constitute a functional material, such as a photonic crystal, or they can be used as a mask to pattern other functional materials, functionalized directly by various chemical approaches, or used as a scaffold to assemble nanoparticles or other nanostructures. BCPs offer tremendous flexibility in creating nanostructured materials with a range of applications in microelectronics, photovoltaics, filtration membranes, and other devices.

Surface textures with three-dimensional (3D) architectures demonstrate the ability to control interfacial, optical, chemical, and mechanical properties. Potential applications range from device-scale biomolecule sensing to meter-scale optical or nonwetting coatings. In recent years, capillary forming has become a versatile and scalable approach to creating complex geometries at the nano- and micron scales. Surface tension of a liquid can deform straight pillars and assemble them into 3D architectures with predetermined orientation, where short-range adhesion forces stabilize the final forms. A variety of techniques have been demonstrated for carbon nanotubes and polymer filamentary materials to fabricate useful devices and textures. We discuss these materials and processes as well as the underlying elasto-capillary physics. We indicate the need for new simulation tools to design and engineer elasto-capillary transformations and methods to increase their throughput toward scalable manufacturing.

Biological surfaces display fascinating topographic patterns such as corrugated blood cells and wrinkled dog skin. These patterns have inspired an emerging technology in materials science and engineering to create self-organized surface patterns by harnessing mechanical instabilities. Compared with patterns generated by conventional lithography, surface instability patterns or so-called ruga patterns are low cost, are easy to fabricate, and can be dynamically controlled by tuning various physical stimuli—offering new opportunities in materials and device engineering across multiple length scales. This article provides a systematic review on the fundamental mechanisms and innovative functions of surface instability patterns by categorizing various modes of instabilities into a quantitatively defined thermodynamic phase diagram, and by highlighting their engineering and biological applications.

In a manner reminiscent of macroscale bending and folding techniques such as origami, the out-of-plane assembly of lithographically micro- and nanopatterned thin films, can be used to fabricate three-dimensional (3D) micro- and nanostructured devices. These 3D devices, including microelectronic circuits, sensors, antennas, metamaterials, robotic, and biomimetic constructs, enable new functionalities and are challenging to fabricate by other methods. In this article, we summarize important features of this set of techniques and the devices assembled thereof, with a focus on functional constructs that have been formed by bending, folding, or buckling. At small size scales, manipulation using manual or even wired probes face daunting practical challenges in terms of cost, scalability, and high-throughput manufacturability; hence we emphasize techniques that manipulate strain in thin films so that they can spontaneously assemble into programmed 3D geometries without the need for any wires or probes.

Materials that can expand and collapse, fold, and transform into a variety of shapes have attracted significant interest and have applications in the design of flexible electronics, color displays, smart windows, actuators, sensors, and both photonic and phononic devices. But how can we render a rigid device super-flexible so that it can wrap around a sphere without bending and stretching? How can flat surfaces be transformed into any desired three-dimensional (3D) structure without disruptive or catastrophic deformation? The key lies in cuts. Here, we review recent research progress in the design of super-conformable and foldable materials by employing fractal cutting and lattice-based kirigami elements that combine cutting and folding. By prescribing cuts with different motifs, identifying edges in the right geometry, and by programming the folding directions, we show that a single flat sheet can be transformed into a variety of targeted 2D and 3D structures—a pluripotent platform for new technologies.

Nanoparticles are ubiquitous in both natural and synthetic environments, providing much of the chemical reactivity for geochemical, planetary, environmental, and technological processes. However, this reactivity and differences between the bulk and nanoscale are thermodynamically, as well as kinetically, controlled. Energetic effects arising from differences in surface energies of different nanomaterials lead to changes in which phases are thermodynamically stable under given conditions. This results in crossovers in polymorphic stability as a function of particle size and substantial shifts in the positions of dehydration and redox equilibria. Examples of these phenomena in aluminum, cobalt, iron, and manganese oxides are presented, and implications for catalysts, battery materials, and other functional oxides are discussed. A hypothesis is presented that low surface energy and the resulting relatively weak water binding on the surface leads to better function when electrons or ions are transferred at the solid-solution interface.