Diamond offers a unique combination of extreme physical properties. For many technological applications, diamond samples of the highest crystal quality are required to utilize the ultimate potential of the material. Specifically, grain boundaries, as in polycrystalline films, have to be avoided. In this article, the two major current approaches of synthesizing single crystal diamond by chemical vapor deposition are described. In homoepitaxy, high gas pressure and high power density microwave discharges facilitating growth rates above 50 µm/h form the basis for the deposition of mm-thick single crystal samples. Cloning and tiling followed by homoepitaxial overgrowth are promising novel concepts aimed at an increase in the lateral dimensions. Heteroepitaxial deposition on large-area single crystals of a foreign material represents a second alternative approach. The state of the art for both concepts is summarized, and current as well as potential future applications are discussed.

Recently, biomaterial scientists have married materials engineering and immunobiology to conceptualize new immunomodulatory materials. This special class of biomaterials can modulate and harness the innate properties of immune functionality for enhanced therapeutic efficacy. Generally, two fundamental strategies are followed in the design of immunomodulatory biomaterials: (1) immuno-evasive (immuno-mimetic, immuno-suppressing, or immuno-inert) biomaterials and (2) immuno-activating or immuno-enhancing biomaterials. This article highlights the development and application of a number of immunomodulatory materials, categorized by these two general approaches.

Over the last few years, significant improvements in sources, columns, detectors, control software, and accessories have enabled a wealth of new focused ion beam applications. In addition, modeling has provided many insights into ion-sample interactions and the resultant effects on the sample. With the knowledge gained, the community has found new ion-beam induced chemistries and ion-beam sources, allowing extending nanostructure fabrication and material deposition to smaller dimensions and better control for direct write and patterning. Insignificant proximity effects in resist-based ion beam lithography, combined with the availability of sub-nm ion spot sizes, opens the way to sub-10 nm structures and dense patterns. Additionally, direct-write ion beam nanomachining can process multilevel structures with arbitrary depths in one single process step, with all the information included in a single standard design file, thus enabling fabrication applications not achievable with any other technique.

The effects of a magnetic field on the current in sandwich devices of a nonmagnetic material in-between two ferromagnetic electrodes are well known. However, magnetic-field effects also occur in the responses of devices of organic semiconductors sandwiched in-between non-ferromagnetic electrodes, providing an entirely new route toward organic spintronics. The precise origins of these “intrinsic” magnetic field effects are still unclear. They appear to be related to spin-selective reactions between paramagnetic entities such as electrons, holes, and triplet excitons. We present an overview of these effects and discuss three recent developments that shed new light on them: (1) tuning of the effects in molecularly engineered systems, (2) the discovery of ultrahigh magnetoresistance in molecular wires, and (3) the discovery of “fringe-field” magnetoresistance.

Ternary semiconducting or metallic half-Heusler compounds with an atomic composition 1:1:1 are widely studied for their flexible electronic properties and functionalities. Recently, a new material property of half-Heusler compounds was predicted based on electronic structure calculations: the topological insulator. In topological insulators, the metallic surface states are protected from impurity backscattering due to spin-momentum locking. This opens up new perspectives in engineering multifunctional materials. In this article, we introduce half-Heusler materials from the crystallographic and electronic structure point of view. We present an effective model Hamiltonian from which the topological state can be derived, notably from a non-trivial inverted band structure. We discuss general implications of the inverted band structure with a focus on the detection of the topological surface states in experiments by reviewing several exemplary materials. Special attention is given to superconducting half-Heusler materials, which have attracted ample attention as a platform for non-centrosymmetric and topological superconductivity.

Neurological pathologies and nerve damage are two problems of significant medical and economic impact because of the hurdles of losing nerve functionality in addition to significant mortality and morbidity, and demanding rehabilitation. There are currently a number of examples of how nanotechnology can provide new solutions for biomedical problems. Current strategies for nerve repair rely on the use of functionalized scaffolds working as “nerve guidance channels” to improve axonal regeneration and to direct axonal re-growth across the nerve lesion site. Since low invasiveness and high selectivity of the growth stimulation are usually conflicting requirements, new approaches are being pursued in order to overcome such limitations. Engineered magnetic nanoparticles (MNPs) have emerged from this need for noninvasive therapies for both positioning and guiding neural cells in response to an external magnetic field. Here, we review the current state of the use of MNPs for neuroprotective and magnetically guided therapies. We discuss some conceivable outcomes of current magnetically driven strategies seeking integrated platforms for regenerative action on damaged tissues.

As Si-transistor technology advances beyond the 10 nm node, the device research community is increasingly looking into the possibility of replacing Si with novel, high mobility materials as the transistor channel. Among several possible candidate materials, germanium and germanium-tin alloys (GeSn) have emerged as strong contenders for the next generation of complementary metal oxide semiconductor (CMOS) transistors. This article presents a comprehensive overview of the state of the art in Ge and GeSn transistor research. We address several key material challenges involved in fabricating high-performance Ge/GeSn-based CMOS transistors, such as gate stack formation and achieving low-resistance contacts to transistor source/drain regions. Using Ge/GeSn as channel materials, we present a FinFET-based, Si-compatible CMOS solution for device dimensions expected in the 7 nm technology node, discuss the practical challenges involved in realizing this design, and highlight directions for future research.

This article describes various techniques for applying strain to current and future complementary metal–oxide–semiconductor (CMOS) channels to boost CMOS performance. A brief history of both biaxial and uniaxial strain engineering in planar CMOS technology is discussed. Scalability challenges associated with process-induced uniaxial strain in sub-22 nm CMOS is highlighted in view of shrinking device dimensions and 3D device architecture (such as fin field-effect transistors [FinFETs]). Non-uniform strain relaxation in patterned geometries in tight pitch two- and three-dimensional devices is addressed. A case is made that the future scalable strain platform will require a combination of biaxial strain at wafer level in conjunction with local uniaxial strain. Finally, potential application of strain engineering to advanced III–V metal oxide semiconductor FET channels will be examined.

“Abundance” is an important keyword in materials development. This is particularly the case for the energy storage sector, where materials themselves function as a storage host. The amount of materials is directly linked to the amount of energy stored in the device. In lithium (Li)-ion batteries, transition metal elements are necessary to accommodate a large number of electrons/holes in a reversible redox reaction. Iron, as the fourth most abundant element in the earth’s crust, is an ideal redox center, but practical storage electrodes with Fe redox have long been the “holy grail” of the Li-ion battery since its commercialization in 1991. In this article, the history of replacing Co with Fe in Li-battery electrodes is briefly reviewed followed by recent technical achievements toward more sustainable batteries using Na+ as a guest ion, where the goal would be to discover a high voltage electrode material composed of Na and Fe without compromising the energy density.

Organic molecules adsorbed on magnetic surfaces offer the possibility to merge the concepts of molecular electronics with spintronics to build future nanoscale data storage, sensing, and computing multifunctional devices. In order to engineer the functionalities of such hybrid spintronic devices, an understanding of the electronic and magnetic properties of the interface between carbon-based aromatic materials and magnetic surfaces is essential. In this article, we discuss recent progress in the study of spin-dependent chemistry and physics associated with the above molecule-ferromagnet interface by combining state-of-the-art experiments and theoretical calculations. The magnetic properties such as molecular magnetic moment, electronic interface spin-polarization, magnetic anisotropy, and magnetic exchange coupling can be specifically tuned by an appropriate choice of the organic material and the magnetic substrate. These reports suggest a gradual shift in research toward an emerging subfield of interface-assisted molecular spintronics.

Nanoparticle (NP) surface properties define how engineered nanomaterials interact with proteins. In aqueous systems, these interactions are driven by the binding of water to NPs and proteins. Understanding the true nature of this NP–water interface and its involvement in the properties of nanomaterials is a fundamental challenge in nanotechnology. Here, we review recent studies on the involvement of water molecules in the interaction of NPs with proteins. We first address the thermodynamic aspects of the NP–protein interaction and the means by which solvation shells can alter the nature of this phenomenon. We then discuss how the chemical nature of the NP surface affects the adsorption of water molecules and how this adsorption can either favor or inhibit protein–NP interactions.

Metal and metal oxide nanoparticles are an important class of materials with numerous applications. Understanding how such nanoparticles interact with living systems is of considerable relevance both from a toxicological and biomedical perspective. The physicochemical features of nanoparticles are sometimes referred to as the synthetic identity, while the acquired properties of nanoparticles in a biological milieu resulting from the adsorption of biomolecules on the surface of the particles can be considered the biological identity. In this article, we explore the dynamic changes in the identity of nanoparticles resulting either from acquisition of a so-called bio-corona or through the process of biotransformation and how this impacts cellular recognition of nanoparticles and toxicological outcomes, with an emphasis on inflammation—an orchestrated host response against harmful stimuli, including pathogens as well as particles.

A wide class of materials that were discovered to carry a topologically protected phase order has led to a highly active area of research called topological insulators (TIs). This phenomenon has radically changed our thinking because of the robust quantum coherent behavior showing two-dimensional Dirac-type metallic surface states (SSs) and simultaneously insulating bulk states. The Dirac SSs are induced by the strong spin–orbit coupling as well as protected by time reversal symmetry (TRS). Breaking TRS in a TI with ferromagnetic perturbation can lead to many exotic quantum phenomena, such as the quantum anomalous Hall effect, topological magnetoelectric effect, as well as image magnetic monopole. This article presents an overview of the current status of TRS breaking in TIs and outlines the prospects for future studies.

Drug delivery systems are becoming increasingly sophisticated, with the ability to target and penetrate specific tissues and release drugs based upon the local environment. While these advanced systems often offer advantages over their less sophisticated counterparts, the final product may be more complex and require additional manufacturing steps. In this article, we review a body of work based on genetically encoded elastin-like polypeptides (ELPs) that offer a route to modular, multifunctional delivery systems that are simple to manufacture. ELPs are temperature-sensitive biopolymers that can be designed on the genetic level and expressed in cell-based protein production systems. The tools of molecular biology and versatility of proteins are used to engineer polymers with precise composition and molecular weight that self-assemble to form drug delivery systems with an impressive variety of features and functions. Due to their versatility and ease of production, ELPs are likely to contribute to the goal of designing simple and effective “smart” delivery systems.

Diamond, because of its unique physical, chemical, and electrical properties and the feasibility of growing it in thin-film form, is an ideal choice as a material for the fabrication of reliable, long endurance, microelectromechanical/nanoelectromechanical systems (MEMS/NEMS). However, various practical challenges, including wafer-scale thickness uniformity, CMOS compatibility, surface micromachining, and, more importantly, controlling the internal stress of the diamond films, make this material more challenging for MEMS engineers. Recent advances in the growth of diamond films using chemical vapor deposition have changed this landscape since most technical hurdles have been overcome, enabling a new era of diamond-based MEMS and NEMS development. This article discusses a few examples of MEMS and NEMS devices that have been fabricated using mono-, nano-, and ultrananocrystalline diamond films as well as their performance.

The evolution of elastic strain engineering in nanostructures and devices requires characterization tools that can be used to not only observe but also quantify the actual strain in a sample, whether this strain is intrinsic or applied. Strain contrast in crystalline samples has always been one of the primary contrast mechanisms used for imaging the microstructure of a material in a transmission electron microscope (TEM). In this regard, TEM is a particularly powerful tool due to its ability to spatially resolve strain information with high precision and spatial resolution. This article reviews the techniques currently available for directly measuring strain in the TEM. Examples are given for measuring strain in semiconductor devices using imaging, diffraction, and holographic techniques. For strain measurement during in situ mechanical testing, two general methods are presented: the conversion of displacement from an actuation device or the direct measurement of strain using image features during deformation.

Ion beams are now widely used to thin, shape, or cut materials on the submicrometer scale. This is possible because ions can sputter (i.e., physically remove) material from the target. Ions can also be used to image materials because the incident beam generates ion-induced secondary electrons (iSE). In both cases, the nature of the target material and the choice of the ion employed and its initial energy will determine not only how quickly the beam can thin a specimen, but also the resolution and contrast of the iSE image that is generated. Clearly, there is a need to be able to predict parameters, such as the nature, information content, and spatial resolution of the iSE image. These and other related questions have been investigated using Monte Carlo simulations. We show how the parameters defining quantities, such as depth of penetration and the energy deposited by the incident beam, or the signal yield and resolution of the iSE image, can be predicted using this approach and how these results make it possible to interpret data and optimize operating conditions.

Fundamental latency and energy limitations are driving major changes in communication and computation hardware. Parallel multicore and multiprocessor architectures are emerging as highly interconnected, communication-centric computation tools that at high node count will approach neural network connectivity and complexity. Monolithically integrated silicon photonics with electronics offers a promising platform for scaling functionality with high volume manufacturing and short design cycle times. The system parameters for this emerging “design for function” paradigm are cost, energy, and bandwidth density. The platform has been built on transmission of a λ ≈ 1550 nm photon wavelength; Si, Ge, Si3N4, and SiO2 materials; and standard complementary metal oxide semiconductor foundry processing. Dimensional shrink is achieved through strong signal confinement in high refractive index contrast material composites. Precision pattern transfer has enabled both photonic interconnect and signal processing functionality. New materials, process integration, and packaging are the keys to success.

Thin-film solid-oxide fuel cells (TF-SOFCs) fabricated using microelectromechanical systems (MEMS) processing techniques not only help lower the cell operating temperature but also provide a convenient platform for studying cathodic losses. Utilizing these platforms, cathode kinetics can be enhanced dramatically by engineering the microstructure of the cathode/electrolyte interface by increasing the surface grain-boundary density. Nanoscale secondary ion mass spectrometry and high-resolution transmission electron microscopy studies have shown that oxygen exchange at electrolyte surface grain boundaries is facilitated by a high population of oxide-ion vacancies segregating preferentially to the grain boundaries. Furthermore, three-dimensional structuring of TF-SOFCs enabled by various lithography methods also helps increase the active surface area and enhance the surface exchange reaction. Although their practical prospects are yet to be verified, MEMS-based TF-SOFC platforms hold the potential to provide high-performance for low-temperature SOFC applications.

This article highlights recent trends and challenges in the area of multicompartmental nanoparticles and focuses on the use of electrohydrodynamic co-jetting for preparing multicompartmental particles, fibers, and cylinders. There are many excellent reviews that have focused on various methods for the fabrication of anisotropic multifunctional particles and fibers and their respective advantages and disadvantages. In this article, we highlight recent developments in the electrohydrodynamic co-jetting approach used for the fabrication of nano- and microparticles and fibers with multifunctional characteristics. A particular focus is given to the use of this technology to control particle size and shape.