Pressure is a key parameter in manufacturing, physical sciences, and life sciences in defining the state of matter. In this issue of MRS Bulletin, we focus on several of the many and diverse domains of advanced materials research where applied pressure (or stress) is used to alter, or otherwise garner information on, material properties. We give an overview of research in which the application of high pressure—often combined with high temperatures and advanced analysis—has led to technological progress, such as in the preparation of superhard materials, in discovering new chemistry for dense forms of low-Z elements, and in the interplay and mimicking of chemical-induced versus pressure-induced structural and electronic changes to prepare new magnetic and energy materials. In addition, the response of materials such as glasses and perovskites to high-stress conditions is discussed, where pressures in the gigapascal regime can easily be achieved in everyday usage. Finally, the structural, dynamical, and phase behavior of biological systems under pressure is explored.

Hydrostatic pressure is an essential physical parameter for studying the structure, dynamics, phase behavior, and free-energy landscape of biomolecular systems. High pressure is an important feature of certain natural environments, and pressure effects on biosystems are of increasing interest for biotechnological applications. Here, we focus on the pressure-dependent activity of enzymes in different environments, from bulk solution to various interfaces. Results were obtained using a high-pressure stopped-flow methodology and high-pressure total internal reflection fluorescence spectroscopy. We highlight that pressure can enhance enzyme activity in various environments, contributing to the fundamental understanding of life under extreme conditions, and elucidate new ways to optimize biotechnological processes.

Single-phase (binderless) superhard nanopolycrystalline diamond and cubic boron nitride (cBN) consisting of fine grains of several tens of nanometers without any secondary phases or binder materials have been developed. These nanopolycrystalline materials are synthesized by direct conversion sintering under ultrahigh pressure and high temperature with optimized and precisely controlled starting materials and synthesis conditions. Their hardness surpasses that of single crystals and conventional sintered compacts and is free from the characteristic cleavage and anisotropy of single crystals. They are especially promising materials for next-generation high-precision, high-efficiency cutting tools and wear-resistant tools. The nanopolycrystalline diamond has excellent potential for precision cutting of nonferrous hard materials, including cemented carbide and hard ceramics, as does the nanopolycrystalline cBN for cutting ferrous hard metals.

High-pressure research, whether static or dynamic, provides “windows” to novel states, transformations, and properties of highly compressed extended states of light elemental solids that may comprise the internal structures of giant planets and stars. These low-Z extended solids are extremely hard, have high energy density, and exhibit novel electronic and nonlinear optical properties—superior to other known materials at ambient conditions. These materials are often formed at formidably high pressures and are highly metastable at ambient conditions; only a few systems have been recovered at ambient conditions, limiting the materials to the realm of fundamental scientific discovery. An exciting new research area has recently emerged that aims to understand and ultimately allow for control of the stability, bonding, structure, and properties of low-Z extended solids. This article presents an overview of the basic principles that govern and control the pressure-induced chemistry in dense solids. This is aimed at identifying high energy density, low-Z extended solids that are amenable to up-scaled synthesis and stabilization at ambient conditions.

In Pixar’s Inside Out, the character Joy proclaims, “Do you ever look at someone and wonder what’s going on inside?” Driven by similar curiosity, the scientific community has developed remarkable in situ characterization tools to visualize the inner workings of complex, dynamic systems, elucidating their functions and enabling next-generation technologies. This article describes our research developing plasmonic techniques to visualize dynamic chemical transformations in situ with nanometer-scale resolution. As a model system, we investigated the hydrogenation and dehydrogenation of palladium nanocrystals. Using environmental electron microscopy and spectroscopy, we monitored this reaction with sub-2-nm spatial resolution and millisecond time resolution. Particles of different sizes, shapes, and crystallinities exhibit distinct thermodynamic and kinetic properties, highlighting several important design principles for next-generation catalysts and energy-storage devices.

It is well recognized that hydrostatic pressure loading can significantly affect the mechanical properties of solids. One of the strongest effects of pressure is the increase in elastic properties of solids. In this article, we address the effect of high pressure on plastic properties through typical examples of the effect of hydrostatic pressure on dislocation core properties of solids.