Volume 20 Issue 4, April 2021

Strong light–matter coupling in quantum cavities provides a pathway to break fundamental materials symmetries, like time-reversal symmetry in chiral cavities. This Comment discusses the potential to realize non-equilibrium states of matter that have so far been only accessible in ultrafast and ultrastrong laser-driven materials.

Classical experiments from solid-state electrochemistry can be used to determine the charge of ions in solids. This Comment also clarifies how the charge of point defects fits with the standard picture of ionic charge, and highlights differences between these electrochemical experiments and methods that probe electrons directly.

Use of polymer and small-molecule semiconductors with relatively poor miscibility helps the long-term stability of the morphology and photovoltaic performance of bulk heterojunction films used in organic solar cells.

Very low-density pulsed current is shown to sharply change the dislocation evolution pattern of Ti–Al alloy with 7 at.% Al, enhancing its strength and ductility.

A multifunctional device produces a much-improved thermoelectric-driven transverse voltage by exploiting a thermoelectric current to drive an anomalous Hall effect in a ferromagnet.

A microporous annealed particle biomaterial has been developed to induce an immune response that can enhance wound healing and tissue repair.

Thermoelectric materials can generate electricity from waste heat but can also use electricity for cooling. This Perspective discusses coefficients of performance for these systems and the state-of-the-art for materials, and suggests strategies for the discovery of improved thermoelectric materials.

Transverse thermeoelectrics can simplify devices as the electric field and heat gradient are perpendicular, but the power output is much less than in standard devices. Here, by forming a closed circuit of thermoelectric and magnetic materials, a much larger transverse thermopower is generated.

Transmission electron microscopy reveals the electroplastic effects in a Ti–Al alloy, which can be uncoupled from Joule heating effects. Electropulsing during deformation enhances wavy slip of dislocations, reconfiguring the dislocation pattern, and hence increases the ductility.

Angle-resolved photoemission evidence for a three-dimensional higher-order topological insulator is presented. This work demonstrates that stacking configurations can be utilized to realize different topological phases.

Scanning electron microscopy is used to image stacking domains in few-layer graphene, as well as moiré patterns in twisted van der Waals heterostructures, allowing for the correlation of the local structure with their excitonic properties.

A magneto-transport study of twisted bilayer graphene near the magic angle further reveals its rich physics.

Ferroelectric superlattices can present a rich variety of phenomena. Here, in PbTiO₃/SrRuO₃ superlattices, it is shown that a complex and stable hierarchical supercrystal can form, with the correlated metal of the SrRuO₃ layers showing large curvatures.

Understanding electrochemical behaviour and stability at solid–solid interfaces remains challenging. Operando synchrotron X-ray computed microtomography loss reveals that reconfiguration of interfacial contact is critical to explain cell failure during solid-state battery cycling.

Understanding the origin of unprecedented solar-to-hydrogen efficiencies in doped SrTiO₃ has proved challenging. Linking in situ charge accumulation to electronic structure in this system now reveals design principles for hydrogen-evolving photocatalysts.

A broad range of characterization techniques is used to understand the dominant electron conduction in various p-type doped π-conjugated polymers, which show p-type and n-type thermoelectric power factors depending on the dopant concentration.

Studies on the morphology stability of polymer donor–small-molecule acceptor blends relevant to solar cell stability reveal relationships between their intermolecular interactions and the thermodynamic, kinetic, thermal and mechanical properties.

Hydrogen doping and polymer adsorption at the oxide surface of liquid metal microparticles increase the conductivity and viscoplastic behaviour of the oxide, leading to liquid-metal-based printed circuits with stable resistance up to 500% strain.

Hierarchically structured 3D materials made of distinct colloidal particles spontaneously assemble by combining the electrostatic modulation of particle interactions to form supracolloids that are organized into 3D structures on solvent drying in an entropy-driven process.

It is now shown that tumour-associated macrophages recruited early during tumour evolution stimulate stromal fibroblasts to express collagen crosslinking enzymes and that the stromal expression, particularly of lysyl hydroxylase 2, can predict survival in a patient cohort.

Microporous annealed-particle degradable scaffolds have been developed and shown to induce type 2 innate and adaptive immune response that facilitated skin wound healing.

Tebello Nyokong, Bokolombe Ngoy and Edith Amuhaya share their experiences in conducting research in Africa.