Stretchable and ultraflexible electronic devices have a broad range of potential uses, from robust devices for energy storage and conversion to biomedical devices that make conformal interfaces with the skin and internal organs. Organics have long been associated with mechanical compliance, which enables inexpensive manufacturing via roll-to-roll printing. This article provides an overview of the use of organic electronic materials, including π-conjugated polymers and small molecules, in highly deformable devices. It begins with a comparison of devices based on organic devices to those based on inorganic composites. The thin-film nature of organic semiconductor devices has also led to the development of several techniques for metrology that can be applied specifically to brittle organic thin films. The article concludes with a brief discussion of the applications of stretchable and ultraflexible organic electronic devices and a prescriptive outlook for successful collaborative work in this exciting, interdisciplinary field.

The rapid increase and dependency on mobile electronic devices and burgeoning importance of sensor network systems and Internet of Things (IoT) to sustain an aging society indicates the strong need to develop battery-less and mobile power sources. Materials for energy harvesting from environmental sources, including mechanical vibrations, magnetic field, heat, and light have become highly relevant for implementation of the IoT vision that requires self-powered wireless sensor networks for sustainable deployment. The articles in this issue cover piezoelectric materials, magnetoelectrics, and thermoelectrics and provide a summary of state-of-the-art energy-harvesting approaches, various material design strategies being targeted by the community, and fundamental challenges in finding an optimum solution and future roadmap. Flexibility of energy harvesters is also emphasized, given the huge potential for wearables. Photovoltaics are briefly covered with respect to wearables and textiles.

This article provides an overview of emerging directions in the materials science of biointegrated electronic and microfluidic systems, as defined by technologies that are capable of supporting long-term, intimate, physical interfaces to living organisms. Here, deterministic hard/soft composite structures, including those that leverage concepts in fractal mathematics, serve as the materials foundations for diverse devices of this type. Examples of “epidermal” or skin-like electronic systems for biophysical tracking of patient conditions that range from stroke to hydrocephalus illustrate the engineering maturity and operational sophistication that is now possible. Recent ideas in soft, skin-mounted, microfluidic lab-on-a-chip systems extend the capabilities of such platforms to include biochemical assessments of physiological status via capture, storage, manipulation, and in situ detection of biomarkers in microliter volumes of sweat, collected as it emerges from the surface of the skin. The article concludes with a description of mechanically guided assembly schemes that provide access to three-dimensional, open-mesh constructs, as a frontier area of materials development in this broader area of biointegrated systems.

This article provides a personal guided tour of multiferroic materials, from their early days as a theoretical curiosity, to their position today as a focus of worldwide research activity poised to impact technology. The article begins with the history of, and the answer to, the question of why so few magnetic ferroelectric multiferroics exist, then gives a survey of the mechanisms and materials that support such multiferroicity. After discussing the tremendous progress that has been made in the magnetoelectric control of magnetic properties using an electric field, some unusual applications of multiferroics in high-energy physics and cosmology are outlined. Finally, the most interesting open questions and future research directions are addressed.

Data are a crucial raw material of this century. The amount of data that have been created in materials science thus far and that continues to be created every day is immense. Without a proper infrastructure that allows for collecting and sharing data, the envisioned success of big data-driven materials science will be hampered. For the field of computational materials science, the NOMAD (Novel Materials Discovery) Center of Excellence (CoE) has changed the scientific culture toward comprehensive and findable, accessible, interoperable, and reusable (FAIR) data, opening new avenues for mining materials science big data. Novel data-analytics concepts and tools turn data into knowledge and help in the prediction of new materials and in the identification of new properties of already known materials.