Significance: For centuries it has been a challenge to avoid strength–ductility trade-off, which is especially problematic for ultrastrong ultrafine-grained metals. Here we evade this trade-off dilemma by architecting a heterogeneous lamella structure, i.e., soft micrograined lamellae embedded in hard ultrafine-grained lamella matrix. The heterogeneous deformation of this previously unidentified structure produces significant back-stress hardening in addition to conventional dislocation hardening, rendering it higher strain hardening than coarse-grained metals. The high back-stress hardening makes the material as strong as ultrafine-grained metals and as ductile as coarse-grained metals.

The strength–ductility trade-off has been a long-standing dilemma in materials science. This has limited the potential of many structural materials, steels in particular. Here we report a way of enhancing the strength of twinning-induced plasticity steel at no ductility trade-off. After applying torsion to cylindrical twinning-induced plasticity steel samples to generate a gradient nanotwinned structure along the radial direction, we find that the yielding strength of the material can be doubled at no reduction in ductility. It is shown that this evasion of strength–ductility trade-off is due to the formation of a gradient hierarchical nanotwinned structure during pre-torsion and subsequent tensile deformation. A series of finite element simulations based on crystal plasticity are performed to understand why the gradient twin structure can cause strengthening and ductility retention, and how sequential torsion and tension lead to the observed hierarchical nanotwinned structure through activation of different twinning systems.

Core–shell nanoparticles (NPs) with lipid shells and varying water content and rigidity but with the same chemical composition, size, and surface properties are assembled using a microfluidic platform. Rigidity can dramatically alter the cellular uptake efficiency, with more‐rigid NPs able to pass more easily through cell membranes. The mechanism accounting for this rigidity‐dependent cellular uptake is revealed through atomistic‐level simulations.

Following the emergence of many novel two-dimensional (2D) materials beyond graphene, interest has grown in exploring implications for fundamental physics and practical applications ranging from electronics, photonics, and phononics to thermal management and energy storage. In this Colloquium, a summary and comparison are given of the phonon properties, such as phonon dispersion and relaxation time, of pristine 2D materials with single-layer graphene to understand the role of crystal structure and dimension on thermal conductivity. A comparison is made of the phonon properties, contrasting idealized 2D crystals, realistic 2D crystals, and 3D crystals, and synthesizing this to develop a physical picture of how the sample size of 2D materials affects their thermal conductivity. The effects of geometry such as the number of layers and the nanoribbon width, together with the presence of defects, mechanical strain, and substrate interactions on the thermal properties of 2D materials are discussed. Intercalation affects both the group velocities and phonon relaxation times of layered crystals and thus tunes the thermal conductivity along both the through-plane and basal-plane directions. This Colloquium concludes with a discussion of the challenges in theoretical and experimental studies of thermal transport in 2D materials. The rich and special phonon physics in 2D materials make them promising candidates for exploring novel phenomena such as topological phonon effects and applications such as phononic quantum devices.