Bioinspiration Across All Length Scales of Materials

摘要

Life appeared on earth more than 3.7 billion years ago.1 Since then, living organisms have constantly adapted to their environment, evolving into an incredible number of species. In this process, highly complex and multifunctional molecules and materials appeared and developed, fulfilling a wide variety of functions. They range from structural support, to sensing, locomotion, and more. In contrast, man-made materials can be optimized only for a limited degree of functionalities, and they are relatively simple when compared to the ones found in the living world. Nevertheless, increasing research efforts are directed toward functional or stimuli-responsive materials that can fulfil multiple or specific functions, adapt to their environment, or interact with biological systems, thus bringing synthetic materials a step closer to biological ones. Not surprisingly, materials scientists, chemists, physicists, biologists, and engineers nowadays look more often at the biological world to study and extract working principles in order to learn methods and concepts for the design and fabrication of novel materials. Some of these concepts are already a commercial reality: Velcro-based adhesives that imitate burrs interlocking into fur, or lotus-like superhydrophobic and self-cleaning surfaces found in glass coatings or façade paints, as well as car pigments mimicking the metallic blue appearance of the Morpho butterfly's wings. Nature is an inexhaustible source of inspiration for materials science well beyond these classic examples. Living organisms have evolved functional materials across all length scales: ranging from functional molecules and molecular machines (e.g., proteins), to self-assembled structures on the nano- and on the microscale (photonic structures, membranes, and reaction compartments such as organelles and cells, adhesive micro- and nanostructures, etc.) to the macroscopic length scale, which is often adopted by engineers, e.g., for load-bearing structures inspired by trees or the capabilities of plants to exert movement without hinges. This Special Issue of Advanced Materials presents bioinspired materials across all length scales, from the molecular level to large civil-engineering structures. Our collection of articles also demonstrates that a successful development and implementation of novel bioinspired functional materials requires a multidisciplinary approach that bridges the length scales and requires the collaboration of biologists studying the biological concept generators, chemists synthesizing novel molecules, physicists shedding light on structure formation on the nano- to microscale, and engineers implementing such novel materials into real-world structures. Bioinspiration can come in many forms, and it is often difficult to clearly define the term, especially as there are also other terms like “biomimetic materials” or “bionic materials” that describe similar ideas, sometimes even the same concept, in the scientific literature. Nevertheless, definitions and technical standards have been recently formulated.2-5 The basic rule to solve material challenges and to develop novel functional materials in a biomimetic way is to analyze a biological system, to abstract the underlying working principle into a model, and to apply this model to the design of a material, independently of their scale. However, in the literature, the term “bioinspired material” is often used in a much looser context to highlight analogies between the working principles of natural materials and synthetic materials, even if the latter were developed without following a biological role model. Nevertheless, such “inverse bioinspiration”, in which the biological system is only sought once the material has been developed, might be a valuable approach to understand the biological systems or to further refine the synthetic material. Before developing novel bioinspired materials it is highly recommended to consult biology for existing knowledge o