5th anniversary

Looking back and contemplating the future at our five-year milestone.

We must all ask ourselves critical questions about our role in the persistence of racism in academia, its effects on our colleagues and intentional actions to improve equity for all.

The first online-only meeting in photonics, held on January 13th 2020, was a resounding success, with 1100 researchers participating remotely to discuss the latest advances in photonics. Here, the organizers share their tips and advice on how to organize an online conference.

Materials research is poised to play a pivotal role in addressing the grand challenges faced by society, from engineering better medicines to providing accessible clean water and renewable energy. However, complex problems require diverse teams. Therefore, there is an urgent need to address the diversity gap in materials science and engineering, especially for women.

On the brink of the next revolution in electronic systems, nanomaterials and, in particular materials that are a few atoms thick are becoming increasingly apparent. Concurrently, computational scientists remain eager to see how Moore's Law will advance.

3D printing enables on-demand solutions for a wide spectrum of needs ranging from personal protection equipment to medical devices and isolation wards. This versatile technology is suited to address supply–demand imbalances caused by socio-economic trends and disruptions in supply chains.

In this Review, the authors analyse the fundamental concepts that govern the photocatalytic performance of organic polymer photocatalysts and discuss the challenges and future of the field of ‘soft photocatalysis’.

The field of DNA nanotechnology takes the DNA molecule out of its biological context and uses its information to assemble structural motifs and connect these motifs together. In this Review, a historical account of the field and the approaches used to assemble DNA nanostructures are outlined, followed by a discussion of emerging applications.

Post-lithium-ion batteries are reviewed with a focus on their operating principles, advantages and the challenges that they face. The volumetric energy density of each battery is examined using a commercial pouch-cell configuration to evaluate its practical significance and identify appropriate research directions.

This Perspective explores and explains the fundamental dogma of nanoparticle delivery to tumours and answers two central questions: ‘how many nanoparticles accumulate in a tumour?’ and ‘how does this number affect the clinical translation of nanomedicines?’

Magnetic skyrmions are topologically protected spin whirls that hold promise for applications because they can be controllably moved, created and annihilated. In this Review, the underlying physics of the stabilization of skyrmions at room temperature and their prospective use for spintronic applications are discussed.

New materials, beyond those that have already obtained regulatory approval, are needed to improve the bioavailability of orally administered proteins. In this Review, barriers to the oral delivery of protein-based therapies are discussed, along with the current translational landscape and state of the art of materials for oral protein delivery.

Plasmonic colours can be used to colour large surfaces, can be mass-produced and dynamically reconfigured, and can provide sub-diffraction resolution. In this Review, basic properties of plasmonic colours, different platforms supporting them and recent developments in the field are discussed.

Unrecycled post-consumer plastic waste is an enormous, growing problem. Chemical recycling to monomer (CRM) delivers recycled material without degradation in properties. This Review assesses the viability of commercial polymer CRM, the flourishing of CRM with new polymers and opportunities for the field.

Nanodiagnostics is a rapidly emerging field that leverages advances in nanobiotechnology to better visualize and diagnose disease. In this Review, we provide an overview of several clinically relevant imaging modalities and discuss how nanodiagnostics are enhancing their use.

Matrigel is widely used for cell culture. However, its ill-defined composition, batch-to-batch variability and animal-derived nature lead to experimental uncertainty and a lack of reproducibility. In this Review, we discuss the limitations of Matrigel and highlight synthetic alternatives for stem-cell culture, regenerative medicine and organoid assembly.

Nanoscale and microscale materials can be used as drug delivery vehicles to target specific lymph node-resident cell subtypes for immunotherapy. In this Review, the authors discuss the transport mechanisms to and from lymph nodes and how they can be explored for drug delivery.

The complexity of biological tissue presents a challenge for engineering of mechanically compatible materials. In this Review, the stiffness of tissue components — from extracellular matrix and single cells to bulk tissue — is outlined, and how this understanding facilitates the engineering of materials with lifelike properties is discussed.

More than twenty 2D carbides, nitrides and carbonitrides of transition metals (MXenes) have been synthesized and studied, and dozens more predicted to exist. Highly electrically conductive MXenes show promise in electrical energy storage, electromagnetic interference shielding, electrocatalysis, plasmonics and other applications.

With a dangling-bond-free surface, two dimensional layered materials (2DLMs) can enable the creation of diverse van der Waals heterostructures (vdWHs) without the conventional constraint of lattice matching or process compatibility. This Review discusses the recent advances in exploring 2DLM vdWHs for future electronics and optoelectronics.

Hydrogel ionotronics employ hydrogels as stretchable, transparent, ionic conductors for the development of ionotronic devices, such as artificial muscles, skins and axons. This Review discusses the mechanical properties and chemistry of materials for hydrogel ionotronic devices and highlights possible applications.

Two-dimensional transition metal dichalcogenides (TMDCs) exhibit attractive electronic and mechanical properties. In this Review, the charge density wave, superconductive and topological phases of TMCDs are discussed, along with their synthesis and applications in devices with enhanced mobility and with the use of strain engineering to improve their properties.

Realizing topological superconductivity and Majorana zero modes in the laboratory is a major goal in condensed-matter physics. In this Review, the rapidly developing field is surveyed, with a focus on the realization of topological superconductivity in semiconductor–superconductor heterostructures.

Sound waves can be manipulated using structurally designed 2D materials of subwavelength thickness. This emerging field, namely, acoustic metasurfaces, is driven by the desire to control acoustic wave propagation using compact devices.

High-entropy alloys have greatly expanded the compositional space for alloy design. In this Review, the authors discuss model high-entropy alloys with interesting properties, the physical mechanisms responsible for their behaviour and fruitful ways to probe and discover new materials in the vast compositional space that remains to be explored.

Organic electrochemical transistors (OECTs) function as a result of ion injection from electrolytes into organic semiconductors. In this Review, the authors discuss OECT physics, organic materials and fabrication technologies, and the application of OECTs in circuits, bioelectronics and memory devices.

Light can initiate chemistries with high spatial and temporal control. In this Review, photoresponsive biomaterials developed for controlled drug delivery and complex tissue engineering are investigated with a focus on photochemistries that provide dynamic precision.

Multiferroic materials exhibit magnetic and ferroelectric order at the same time and provide a way to control magnetism with electric fields. We discuss the mechanisms supporting multiferroicity, multiferroic thin films and heterostructures, the non-equilibrium dynamics of multiferroics, fundamental symmetry issues and the impact of multiferroics on other research areas.

Introducing multiplicity and variation into the components of metal–organic frameworks has emerged as new fascinating directions in reticular chemistry. In this Review, the variances in the framework backbone, functionality and metal, and their leading to sequences of chemical information, are highlighted. Anisotropy in these structures is imposed by the variance and realized along a specific direction.

Thermoelectrics can be used to harvest energy and control temperature. Organic semiconducting materials have thermoelectric performance comparable to many inorganic materials near room temperature. Better understanding of their performance will provide a pathway to new types of conformal thermoelectric modules.

Despite their excellent macroscopic operational parameters, halide perovskites exhibit heterogeneity in materials properties at all lateral and vertical length scales. In this Review, we discuss the nature of heterogeneity in halide perovskites and assess the impact of these non-uniformities on their optoelectronic properties and how the heterogeneity may even be beneficial for device properties.

Organ-on-a-chip devices can recreate key aspects of human physiology in vitro, offering an alternative to animal models for preclinical drug testing. This Review examines how tissue barrier properties, parenchymal tissue function and multi-organ interactions can be recreated in organ-on-a-chip systems and applied for drug screening.