This article addresses why biomaterials are a growing part of materials science. We consider two areas at two different scales. At the nanometer scale, enzymes are heterogeneous nanoparticles of extraordinary deformability; this property allows us to view biomolecules informed by concepts of materials science and nonlinear physics. A degree of universality in the mechanical behavior of the molecules appears in the ubiquitous softening transitions; some results obtained dynamically by nanorheology, and others obtained in equilibrium experiments through the method of the DNA springs are summarized. These soft molecules represent an opportunity for studies of dissipation at the atomic scale. At the mesoscopic scale, composite functional materials with biological components hold promise for applications such as low power, chemically driven, biodegradable devices. A concrete example, and a program for the future, is the artificial axon. It is a synthetic structure that supports action potentials based on the same physical mechanism as the voltage spikes in nerve cells. A network of such axons, which is yet to come, would constitute an artificial brain. Beyond device applications, the focus here is on the basic science, namely, a constructivist approach to cybernetics, algorithmic mathematics, and the brain.

In this paper, in situ Al4C3 and carbon nanotubes (CNTs) hybrid-reinforced aluminum matrix composites were prepared by a two-step ball milling (TSBM), consisting of a 24-h long-time ball milling (LTBM) and a 6-h short-time ball milling (STBM). During LTBM, most of the CNTs were seriously damaged, and many amorphous carbon atoms derived from these damaged defects would react with Al powder to form in situ Al4C3 nanorods. Subsequently, 1 wt% CNTs were added into the composite powders for STBM to uniformly disperse CNTs into the composite powders. Compared with that of the composite prepared by one-step ball milling, the comprehensive mechanical properties of the composite prepared by the TSBM are improved obviously due to the synergistic effects of in situ Al4C3 and CNTs, and the tensile strength and elongation reached 258 MPa and 19.5%, respectively. The strengthening mechanisms of TSBM composite include fine-grained strengthening, dispersion strengthening by in situ Al4C3, and load transfer from matrix to CNTs.

To suppress the interface gap between the cell walls of wood and filled epoxy resin, a green and universal H2O2 or H2O2/HAc steam-modified delignification approach is developed to remove more lignin, thereby generating more pores to be more conveniently backfilled by epoxy resin for highly transparent wood composites. Utilizing the excellent penetration ability of steam, not only different wood species, such as basswood and pine, with different cutting directions but also the thickest (40 mm) and largest (210 × 190 mm) wood samples can be successfully delignified. Compared with the 1.9% lignin content (which is the normal content of delignified wood prepared by solution-based methods) of delignified wood, the as-prepared delignified wood has the lowest lignin content of 0.84% to date. After the infiltration of epoxy resin, not only did the mechanical strength of the 5-mm transparent wood composite increase from 12.5 to 20.6 MPa, but the transmittance (the wavelength was 550 nm) also increased from 80 to 87% due to the lower absorbance of visible light by lignin and the suppression of the interface debonding gap between the cell walls and the backfilled epoxy resin.

Searching for materials with improved or perhaps completely novel properties involves an iterative process intended to successively narrow the gap between some initial starting point and the desired design target. This can be viewed as an optimization problem in a high-dimensional search space, often with many dozens of material parameters that need to be tuned. To tackle this, the evolutionary process in biology has been a source of inspiration in developing effective search algorithms. However, reaping the full benefits of bioinspired searches for materials design requires some thought. Here, we go beyond traditional black box algorithms and take a broader view of computational evolution strategies. We discuss recent strategies that exploit knowledge about the material configuration statistics and we highlight the advantages when time-varying environments are considered. Throughout, we emphasize that the search strategies themselves can be viewed as a nonequilibrium dynamical process in design space.

Traditional approaches to materials synthesis have largely relied on uniform, equilibrated phases leading to static “condensed-matter” structures (e.g., monolithic single crystals). Departures from these modes of materials design are pervasive in biology. From the folding of proteins to the reorganization of self-regulating cytoskeletal networks, biological materials reflect a major shift in emphasis from equilibrium thermodynamic regimes to out-of-equilibrium regimes. Here, equilibrium structures, determined by global free-energy minima, are replaced by highly structured dynamical states that are out of equilibrium, calling into question the utility of global thermodynamic energy minimization as a first-principles approach. Thus, the creation of new materials capable of performing life-like functions such as complex and cooperative processes, self-replication, and self-repair, will ultimately rely upon incorporating biological principles of spatiotemporal modes of self-assembly. Elucidating fundamental principles for the design of such out-of-equilibrium dynamic self-assembling materials systems is the focus of this issue of MRS Bulletin.

Biological entities are capable of amazing material feats, such as self-organization, self-repair, self-replication, and self-immolation. Indeed, the most intriguing feature of living biomaterials, whether they are tissues, cells, or intracellular structures, is their ability to autonomously sense, decide, and perform work without the need of a project manager. The effect is multiscale—from enzymes to full organisms, each level is capable of such autonomous activities. Further, each scale has similar energy-using units that work together to compose the larger-scale material. For instance, autonomous cells work together to create tissues. In this article, we will discuss some of the outstanding and desirable properties of active biological materials that we might consider mimicking in future materials. We will discuss how such active materials are powered and explore some fundamental lessons we can learn to direct future fundamental scientific inquiries to begin to understand and use these properties to make synthetic, autonomous materials of the future.

In situ TiB2 particles with polyhedral or near-spherical morphology with more high-index crystal planes exposed were prepared by controlling the addition amount of Sc in commercial pure aluminum matrix. As the content of Sc increased, TiB2 morphology transformed from hexagonal platelets to polyhedral or near-spherical morphology with a decrease in particle size. In the present paper, a simple method to prepare near-spherical in situ TiB2 particles in Al matrix was explored and it was found that the reinforcement distribution was improved significantly. The different growth mechanism of TiB2 particles in Al and Al–Sc systems was discussed. The key reason for the morphology evolution was that the Sc was preferentially adsorbed on ${\bf \left\{ {1{\bf \overline{2}}12} \right\}}$, ${\bf \left\{ {11\overline{2}0} \right\}}$, and ${\bf \left\{ {10\overline{1}1} \right\}}$ which would inhibit the growth of these faces effectively and retain a lower-energy state of the polyhedral or quasispherical TiB2 particles in Al–Sc systems.

We report the synthesis of a novel polymer gel electrolyte primarily based on cellulose extracted from wood along with gelatin, polyacrylic acid (PAA) and potassium hydroxide (KOH) added as additives in minute amounts in various stages. We also study and report the variation of ionic conductivity with variation of various additives. We found that, with variation of additives to hydrogel, its stability and degree of crystallinity are varied. The results were confirmed using x-ray diffraction and Fourier transform infrared spectra studies. An average best ionic conductivity of 96.89mS/cm was reported for a hydrogel: gelatin: PAA: KOH system, which is one of the best reported values of ionic conductivity for gel electrolytes.

A principal mode of corrosion in combustion or fuel cell environments is the formation of volatile hydroxides and oxyhydroxides from metal or oxide surfaces at high temperatures. It is important to determine the degree of volatility and accurate thermodynamic properties for these hydroxides. Significant gaseous metal hydroxides/oxyhydroxides are discussed, along with available experimental and theoretical methods of characterizing species and determining their thermodynamic properties.

The effects of specimen size, Hall–Petch (H-P) grain or subgrain size, particle size plus spacing, and crack size on the yield strength, plastic deformation, and fracturing properties of crystalline materials are described on a dislocation mechanics basis. The size effects are assessed at relevant macro- and/or micro-and/or nano-scale dimensions; in the latter case, at the upper-limiting strength levels. The description is applied mostly to face-centered cubic (FCC), body-centered cubic (BCC), and hexagonal close-packed (HCP) metals but also involves grain size/particle size–dependent (composite) steel material behaviors. Competition is described for the role of dislocation pile-ups versus hole-joining mechanisms for ductile failure. Grain size–dependent microhardness and strain rate sensitivity measurements are presented for nano-grain size strengthening and grain size weakening, respectively. An intrinsic size effect is demonstrated for silicon crystal nano-indentation hardness testing, which, on microscale loading, leads to evaluation of crack size dependence and, for polycrystalline alumina, to associated H-P behavior for the fracture mechanics stress intensity.

Asymmetric membranes present promising characteristics for wound dressing applications. A porous structure uptakes the wound exudate, whereas an occlusive layer (upper film) inhibits the microbial penetration and prevents an excessive loss of water. Konjac glucomannan (KGM) is a natural polysaccharide that has been investigated as wound dressings in the form of films, sponges, and hydrogels due to its flexibility, swelling capacity, biocompatibility, and low cost. However, there are no studies on literature regarding the development of KGM asymmetric membranes. In this study, we investigated a new casting–freezing process for the production of KGM asymmetric membranes. The scanning electron microscopy and thermogravimetric analyses indicated an asymmetric morphology and a good thermal stability of the membrane samples, respectively. Moreover, biological, mechanical, and fluid-handling capacity tests showed that the membrane is biocompatible and resistant to handling structure, which was also able to retain the ideal moist conditions for wound healing.