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Surface curvature both emerges from, and influences the behavior of, living objects at length scales ranging from cell membranes to single cells to tissues and organs. The relevance of surface curvature in biology is supported by numerous experimental and theoretical investigations in recent years. In this review, first, a brief introduction to the key ideas of surface curvature in the context of biological systems is given and the challenges that arise when measuring surface curvature are discussed. Giving an overview of the emergence of curvature in biological systems, its significance at different length scales becomes apparent. On the other hand, summarizing current findings also shows that both single cells and entire cell sheets, tissues or organisms respond to curvature by modulating their shape and their migration behavior. Finally, the interplay between the distribution of morphogens or micro-organisms and the emergence of curvature across length scales is addressed with examples demonstrating these key mechanistic principles of morphogenesis. Overall, this review highlights that curved interfaces are not merely a passive by-product of the chemical, biological, and mechanical processes but that curvature acts also as a signal that co-determines these processes., (© 2023 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

Inspired by the motions of plant tissues in response to external stimuli, significant attention has been devoted to the development of actuating polymeric materials. In particular, polymeric actuators driven by organic molecules have been designed due to their combined superiorities of tunable functional monomers, designable chemical structures, and variable structural anisotropy. Here, the recent progress is summarized in terms of material synthesis, structure design, polymer-solvent interaction, and actuating performance. In addition, various possibilities for practical applications, including the ability to sense chemical vapors and solvent isomers, and future directions to satisfy the requirement of sensing and smart systems are also highlighted., (© 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Surface structuring of titanium-based implants is known to modulate the behavior of adherent cells, but the influence of different nanotopographies is poorly understood. The aim is to investigate preosteoblast proliferation, adhesion, morphology, and migration on surfaces with similar surface chemistry but distinct nanotopographical features. Sonochemical treatment and anodic oxidation are employed to fabricate disordered, mesoporous titania (TMS) and ordered titania nanotubular (TNT) topographies on titanium, respectively. Morphological evaluation reveals that cells are polygonal and well-spread on TMS, but display an elongated, fibroblast-like morphology on TNT surfaces, while they are much flatter on glass. Both nanostructured surfaces impair cell adhesion, but TMS is more favorable for cell growth due to its support of cell attachment and spreading in contrast to TNT. A quantitative wound healing assay in combination with live-cell imaging reveals that cell migration on TMS surfaces has a more collective character than on other surfaces, probably due to a closer proximity between neighboring migrating cells on TMS. The results indicate distinctly different cell adhesion and migration on ordered and disordered titania nanotopographies, providing important information that can be used in optimizing titanium-based scaffold design to foster bone tissue growth and repair while allowing for the encapsulation of drugs into porous titania layer., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Teeth are designed to deliver high forces while withstanding the generated stresses. Aside from isolated mineral-free exception (e.g., marine polychaetes and squids), minerals are thought to be indispensable for tooth-hardening and durability. Here, the unmineralized teeth of the giant keyhole limpet (Megathura crenulata) are shown to attain a stiffness, which is twofold higher than any known organic biogenic structures. In these teeth, protein and chitin fibers establish a stiff compact outer shell enclosing a less compact core. The stiffness and its gradients emerge from a concerted interaction across multiple length-scales: packing of hydrophobic proteins and folding into secondary structures mediated by Ca 2+ and Mg 2+ together with a strong spatial control in the local fiber orientation. These results integrating nanoindentation, acoustic microscopy, and finite-element modeling for probing the tooth's mechanical properties, spatially resolved small- and wide-angle X-ray scattering for probing the material ordering on the micrometer scale, and energy-dispersive X-ray scattering combined with confocal Raman microscopy to study structural features on the molecular scale, reveal a nanocomposite structure hierarchically assembled to form a versatile damage-tolerant protein-based tooth, with a stiffness similar to mineralized mammalian bone, but without any mineral., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The first hygroscopically tunable cloth actuator is realized via impregnation of a commercial cloth template by a three dimensionally (3D) nanoporous polymer/carbon nanotube hybrid network. The nanoporous hybrid guarantees diffusion of water into the cloth actuator and amplifies the deformation scale. The cloth actuators are mechanically stable with high tensile strength. Because the commercial cotton cloth is inexpensive, such actuators capable of complex motions can be produced in a large size and scale for a wide variety of utilities (e.g. electric generators and "smart" materials)., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)