Review Articles in 2018

The stress that a material can sustain before fracture increases as the sample size decreases. This size effect is associated with the defects present in a material. In this Review, we explore this size effect in micro- and nanoscale materials from experimental and theoretical perspectives.

Point defects have a key role in determining the performance of photovoltaic materials. In this Review, we assess defect processes in a range of photovoltaic materials and outline how point defect engineering could be used to improve the efficiency of solar cells.

Endogenous stem cells play a key role in the repair and remodelling of tissues and organs in the body. This Review discusses endogenous stem cell populations of different tissues and investigates regeneration approaches in combination with natural and synthetic biomaterials.

In quantum materials, ultrashort light pulses can induce transitions between electronic phases, switch ferroic orders and unveil non-equilibrium emergent behaviours. Here, we review the use of femtosecond X-ray pulses in tracking the underlying dynamics of the structural, electronic and magnetic order in these systems.

The extracellular matrix is nature’s template for an ideal biomaterial to guide tissue homeostasis and repair. In this Review, matrix-mimicking biomaterials and decellularized matrices are discussed for their potential to reconstruct and repair tissues in vitro and in vivo.

Soft robots have broad applications in medicine. In this Review, biomedical applications, including surgery, drug delivery, prostheses, wearable devices and artificial organs, are discussed in the context of materials, actuation strategies and challenges.

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.

Microrobots are envisioned to revolutionize microsurgery and targeted drug delivery. Their design, operation, locomotion and interaction with the environment are inspired by microorganisms. This Review highlights soft, responsive and active materials for the development of (semi-)autonomous microrobots.

Inspired by biological systems, engineers are exploring origami folding with smart material actuation to enable intrinsically actuated designs with complex functionalities and easy fabrication. This Review highlights recent advances in the design, fabrication and control of these origami robots.

3D printing can be used to directly fabricate soft robots. This Review discusses advances in 3D printing technologies and soft materials for the fabrication of soft robotic systems with sophisticated capabilities, such as 3D movement and responsiveness to the environment.

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.

Atom-like quantum emitters in solids have emerged as promising building blocks for quantum information processing. In this Review, recent advances in three leading material platforms—diamond, silicon carbide and atomically thin semiconductors—are summarized, with a focus on applications in quantum networks

Biofabrication can be applied to replicate tissues and organs for regenerative medicine and for the creation of 3D in vitro tissue models. In this Review, the recent advances in biomaterials and biofabrication technologies are discussed, and challenges and opportunities are highlighted.

Thermally activated delayed fluorescence (TADF) emitters are promising electroluminescent materials for next-generation organic light-emitting diodes (OLEDs). In this Review, the molecular design, photophysical characteristics and OLEDs composed of small-molecule, dendritic and polymeric TADF emitters are discussed.

Nanofibrils are abundant and critical structural components in nature that can be exploited for novel and sustainable materials. In this Review, hierarchical design strategies for cellulose, silk and chitin nanofibrils in nature and in materials engineering are discussed.

Perovskite solar cells (PSCs) have emerged as a revolutionary class of photovoltaic technology. Here, we review recent progress and challenges in scaling up PSCs towards commercialization. We discuss several areas, including device architectures, deposition methods, scalable deposition of perovskite and charge transport layers, device stability, module-level characterization and techno-economic analyses.

Carbon nanomaterials have greatly advanced non-volatile memory technology. In this Review, applications of various carbon nanomaterials as memory electrodes, interfacial engineering layers, memory selectors and resistive-switching media are discussed in the context of emerging non-volatile memory devices.

Experimental and computational studies reveal numerous aspects of the molecular and hierarchical structure of spider silk and of its molecular dynamics. In this Review, we discuss the structure–function relationships of spider silk that can be elucidated from these studies and how this knowledge may enable the reverse engineering of spider silk.

Non-fullerene acceptors have been widely used in organic solar cells over the past 3 years. This Review focuses on the two most promising classes of non-fullerene acceptors — rylene diimide-based materials and fused-ring electron acceptors — and discusses structure–property relationships, donor– acceptor matching criteria and device physics, as well as future research directions for the field.

Material engineering offers the possibility to guide the fate of mesenchymal stem cells (MSCs). This Review highlights integrin–growth factor receptor crosstalk mechanisms in MSC growth and differentiation, and material design strategies to trigger the synergistic signalling of integrins and growth factor receptors.