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Topological phononic crystals, alike their electronic counterparts, are characterized by a bulk–edge correspondence where the interior of a material dictates the existence of stable surface or boundary modes. In the mechanical setup, such surface modes can be used for various applications such as wave guiding, vibration isolation, or the design of static properties such as stable floppy modes where parts of a system move freely. Here, we provide a classification scheme of topological phonons based on local symmetries. We import and adapt the classification of noninteracting electron systems and embed it into the mechanical setup. Moreover, we provide an extensive set of examples that illustrate our scheme and can be used to generate models in unexplored symmetry classes. Our work unifies the vast recent literature on topological phonons and paves the way to future applications of topological surface modes in mechanical metamaterials.

Conventional synthetic materials have fixed mechanical properties and suffer defects, damage, and degradation over time. This makes them unable to adapt to changing environments and leads to limited lifecycles. Recently, self-adaptive materials inspired by natural materials have emerged as a solution to address these problems. With the ability to change their mechanical properties based on changing mechanical environments, repairing defects, and maintaining their mechanical properties, these materials can lead to improved performance while decreasing waste. In this review, we explore self-adaptive phenomena found in nature that have inspired the development of synthetic self-adaptive materials, and the mechanisms that have been employed to create the next generation of materials. The potential applications of these materials, the challenges that existing approaches face, and future research opportunities are also discussed.

There has been concerted effort across scientific disciplines to develop artificial materials and systems that can help researchers understand natural stimuli-responsive activities. With its up-to-date coverage on intelligent stimuli-responsive materials, Intelligent Stimuli-Responsive Materials provides research, industry, and academia professionals with the fundamentals and principles of intelligent stimuli-responsive materials, with a focus on methods and applications. Emphasizing nanostructures and applications for a broad range of fields, each chapter comprehensively covers a different stimuli-responsive material and discusses its developments, advances, challenges, analytical techniques, and applications.

This article explores the transformative advances in soft machines, where biology, materials science, and engineering have converged. We discuss the remarkable adaptability and versatility of soft machines, whose designs draw inspiration from nature’s elegant solutions. From the intricate movements of octopus tentacles to the resilience of an elephant’s trunk, nature provides a wealth of inspiration for designing robots capable of navigating complex environments with grace and efficiency. Central to this advancement is the ongoing research into bioinspired materials, which serve as the building blocks for creating soft machines with lifelike behaviors and adaptive capabilities. By fostering collaboration and innovation, we can unlock new possibilities in soft machines, shaping a future where robots seamlessly integrate into and interact with the natural world, offering solutions to humanity’s most pressing challenges.

HighlightsThe 2D CoOOH sheet-encapsulated Ni2P into tubular arrays electrocatalytic system with expediting mass transport, structural stability, and tuned electron was conceptually proposed.The designed electrocatalysts realize expectant 1000 mA cm−2-level-current-density hydrogen evolution in neutral water for over 100 h.Water electrolysis at high current density (1000 mA cm−2 level) with excellent durability especially in neutral electrolyte is the pivotal issue for green hydrogen from experiment to industrialization. In addition to the high intrinsic activity determined by the electronic structure, electrocatalysts are also required to be capable of fast mass transfer (electrolyte recharge and bubble overflow) and high mechanical stability. Herein, the 2D CoOOH sheet-encapsulated Ni2P into tubular arrays electrocatalytic system was proposed and realized 1000 mA cm−2-level-current-density hydrogen evolution over 100 h in neutral water. In designed catalysts, 2D stack structure as an adaptive material can buffer the shock of electrolyte convection, hydrogen bubble rupture, and evolution through the release of stress, which insure the long cycle stability. Meanwhile, the rich porosity between stacked units contributed the good infiltration of electrolyte and slippage of hydrogen bubbles, guaranteeing electrolyte fast recharge and bubble evolution at the high-current catalysis. Beyond that, the electron structure modulation induced by interfacial charge transfer is also beneficial to enhance the intrinsic activity. Profoundly, the multiscale coordinated regulation will provide a guide to design high-efficiency industrial electrocatalysts.

Guiding energy deliberately is one of the central elements in engineering and information processing. It is often achieved by designing specific transport channels in a suitable material. Topological metamaterials offer a way to construct stable and efficient channels of unprecedented versatility. However, due to their stability it can be tricky to terminate them or to temporarily shut them off without changing the material properties massively. While a lot of effort was put into realizing mechanical topological metamaterials, almost no works deal with manipulating their edge channels in sight of applications. Here, we take a step in this direction, by taking advantage of local symmetry breaking potentials to build a switchable topological phonon channel.

Dynamic controllability of self‐organized helical superstructures in spatial dimensions is a key step to promote bottom‐up artificial nanoarchitectures and functional devices for diverse applications in a variety of areas. Here, a light‐driven chiral overcrowded alkene molecular motor with rod‐like substituent is designed and synthesized, and its thermal isomerization reaction exhibits an increasing structural entropy effect on chemical kinetic analysis in anisotropic achiral liquid crystal host than that in isotropic organic liquid. Interestingly, the stimuli‐directed angular orientation motion of helical axes in the self‐organized helical superstructures doped with the chiral motors enables the dynamic reconfiguration between the planar (thermostationary) and focal conic (photostationary) states. The reversible micromorphology deformation processes are compatible with the free energy fluctuation of self‐organized helical superstructures and the chemical kinetics of chiral motors under different conditions. Furthermore, stimuli‐directed reversible nonmechanical beam steering is achieved in dynamic hidden periodic photopatterns with reconfigurable attributes prerecorded with a corresponding photomask and photoinduced polymerization. Stimuli‐directed dynamic controllability of reconfiguration between planar and focal conic states is demonstrated in self‐organized helical superstructures doped with chiral molecular motors. The reversible reconfiguration is compatible with the chemical kinetics of chiral molecular motors under different conditions, thus functioning in the temporal evolution of nonmechanical 1D diffraction prerecorded with photomask and photoinduced polymerization.

Biological materials in nature are inherently adaptive, evolving through continuous interaction with their environment. Achieving such adaptability and self‐optimization in artificial materials remains a major challenge. In this work, a simple yet robust mechanism is introduced that enables instantaneous changes in local stiffness components in response to strain. This is realized by designing binary meta‐capsules with two discrete states 0 and 1, each corresponding to a different modulus in one direction. These strain‐responsive capsules switch states based on applied deformation, serving as the building blocks for a new class of adaptive mechanical metamaterials (AMMs). Computational tools are developed to guide the design, and selected structures are fabricated via multi‐material polymer jetting. Mechanical experiments, including compression and indentation tests, confirm the functionality of the AMMs. Because the stiffness change in each meta‐capsule is reversible, the material can reconfigure itself after loading‐unloading cycle. This enables AMMs to dynamically adjust their local properties based on external loads and/or constraints, effectively “reprogramming” or redesigning themselves post‐fabrication, paving the way for transforming 3D/4D printing into adaptive, “infinity‐D” printing. Inspired by nature's adaptivity, this work presents a new class of mechanical metamaterials that can reversibly switch local stiffness in response to local strain. Using strain‐triggered binary meta‐capsules as building blocks, these materials dynamically reconfigure their properties under load, enabling embodied intelligence and paving the way toward truly adaptive, reprogrammable “infinity‐D” printed structures.