The drive for greater use of renewable materials is one that has recently gained momentum due to the need to rely less heavily on petroleum. These renewable materials are defined as such since they are derived from plant-based sources. Some renewable materials also offer properties that conventional materials cannot provide: hierarchical structure, environmental compatibility, low thermal expansion, and the ability to be modified chemically to suit custom-made applications. Nature's materials, particularly from plant- and animal-based polysaccharides and proteins, have hierarchical structures, and these structures can be utilized for conventional applications via biomimetic approaches. This issue begins with an article covering renewable polymers or plastics that can be used to generate block copolymers (where two polymers with specific functions are combined) as an alternative to conventional materials. Applications of renewable polymers, such as cellulose from plants, bacteria, and animal sources, are also covered. Also presented are the use of bacterial cellulose and other plant-based nanofibers for transparent electronic display screens and, in a wider sense, the use of cellulose nanofibers for composite materials, where renewable resources are required to generate larger amounts of material. Finally, this issue shows the use of biomimetic approaches to take the multifunctional properties of renewable materials and use these concepts, or the materials themselves, in conventional materials applications.

Hybrid macromolecules composed of two or more covalently connected segments have the ability to self-assemble into nanostructured materials. These fascinating materials are used in applications ranging from footwear to bitumen modification to microelectronics. The number of technologies that utilize or could benefit from multiphase polymers is expanding at a rapid rate. This growth is due to the development of simple scalable synthetic technologies, a deeper understanding of their structure-property relationships, and their effectiveness as low-level additives. As industrial uses of self-assembled polymers become more prevalent, there will be a heightened focus on alternative preparative approaches that do not rely on petroleum feedstocks. Therefore the development of biorenewable multiphase polymers is an important research endeavor. In this article, we will explore the synthesis, self-assembly, and properties of renewable block and graft copolymers that contain aliphatic polyesters, as well as bio-sourced segmented polyurethanes. These two classes of multiphase polymers are the most promising and practical candidates for implementation in the next generation of sustainable materials.

Cellulose biocomposites are widely used in industry as a low-cost engineering material with plant fiber reinforcement. However, chemical and microstructural heterogeneity causes low strength, low strain-to-failure, high moisture sensitivity, and odor and discoloration problems. Efforts toward improved performance through fiber orientation control, increased fiber lengths, and biopolymer use are reviewed. Interfacial strength control and moisture sensitivity are remaining challenges. As an attractive alternative reinforcement, high-quality cellulose nanofibers obtained by wood pulp fiber disintegration can be prepared at low cost. These nanofibers have high length/diameter ratios, diameters in the 5–15 nm range, and intrinsically superior physical properties. Wood cellulose nanofibers are interesting as an alternative reinforcement to more expensive nanoparticles, such as carbon nanotubes. Nanopaper and polymer matrix nanocomposites based on cellulose nanofiber networks show high strength, high work-of-fracture, low moisture adsorption, low thermal expansion, high thermal stability, high thermal conductivity, exceptional barrier properties, and high optical transparency. The favorable mechanical performance of bioinspired foams and low-density aerogels is reviewed. Future applications of cellulose biocomposites will be extended from the high-volume/low-cost end toward high-tech applications, where cellulose properties are fully exploited in nanostructured materials.

Nanocellulose, such as that produced by the bacteria Gluconacetobacter xylinus (bacterial cellulose, BC), is an emerging biomaterial with great potential as a biological implant, wound and burn dressing material, and scaffolds for tissue regeneration. BC has remarkable mechanical properties despite the fact that it contains up to 99% water. The water-holding ability is the most probable reason why BC implants do not elicit any foreign body reaction. Moreover, the nanostructure and morphological similarities with collagen make BC attractive for cell immobilization and cell support. The architecture of BC materials can be engineered over length scales ranging from nano to macro by controlling the biofabrication process. This article describes current and future applications of BC in the biomedical field.

Organic light-emitting diodes bring a whole new level of image quality, power consumption, and very thin profiles to displays. In addition, with the appropriate choice of a flexible substrate, paper-like flexible displays that are lightweight, robust, and conformable can be produced. This will make it possible to roll or fold the displays for portability or incorporate them in clothing as wearable displays. Plastic substrates are considered prospective materials due to their inherent flexibility and optical qualities. However, one of the major drawbacks of plastics is the large thermal expansion. The thermal expansion of the substrate has to be compatible with those of the layers deposited on it, otherwise these layers will become strained and crack during the thermal cycling involved in the display manufacture. One of the proposed solutions to reduce the thermal expansion of plastics without appreciable loss in transparency is to reinforce them with nanofibers. These nanofibers are already available in enormous quantities in nature, in the form of cellulose, with the caveat that they have to be extracted properly. Here we present the methodologies required to obtain the cellulose nanofibers and to produce optically transparent composites for use in flexible displays.

Natural materials display a wealth of structures and fulfill a variety of functions. Hierarchical structuring is one of the keys to providing multifunctionality and to adapting to varying needs of an organism. As a consequence, the natural environment represents not only a direct and renewable source of useful materials, such as wood, plant fibers, or even proteins of pharmaceutical importance, but also an enormous “database” of structures with exceptional mechanical, optical, or magnetic properties. Rather than focusing on the direct use of natural materials, this article discusses the use of structures that appeared in evolution and have been implemented in artificial materials of an entirely different type and chemical composition. This may be done either by directly copying the structure (biotemplating) or by extracting the design principles encoded in them for the fabrication of novel bioinspired materials.

Ferroelectric oxides underwent a renaissance in the 1980s and 1990s, driven by the success in commercializing thin-film ferroelectric random-access memory devices (FRAMs) for applications such as the SONY PlayStation 2 memory board. Materials scientists gravitated into this new field from magnetic oxides and from high-Tc superconductivity. But as the FRAM prospects wane and neither dynamic random-access memory devices nor FLASH memory has been replaced, we now require new directions for materials research on oxides. In this article, I outline briefly four new directions for ferroelectric oxide research: something old—ferroelectrically induced ferromagnetism and multiferroic switching; something new—THz emission from oxide ferroelectrics; something borrowed—Heisenberg-like switching of domains in nanoferroelectrics; and something blue—ZnO light-emitting devices. Magnetoelectricity—the linear coupling of polarization and magnetization—was theoretically predicted by Igor Dzyaloshinskii in 1957 and measured experimentally by Astrov two years later. It did not produce commercial devices. Although a flurry of new work occurred in the 1970s, emphasizing boracites—mostly by Hans Schmid in Geneva, no materials were found that exhibited large effects at room temperature. In the past decade, the search has been renewed, emphasizing rare earth systems such as Tb manganites.