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Natural systems and processes

Natural systems, such as biological materials, have the ability to sense, react, regulate, grow, regenerate and heal themselves. Biological materials constitute most of the bodies of plants and animals around us. They allow cells to function, eyes to capture and interpret light, plants to respond to the light and animals to move or fly. This multitude of operations has always inspired mankind to make materials and devices, which simplify many of our day-to-day functions. One remarkable property of natural materials and structures is their ability of self-sealing and self-healing. Many animals and plants regenerate tissues or even whole organs after injury. However, biological repair processes are generally very complex and an adaption into a technical system is not easy. Recent advances in chemistry and microand nanoscale fabrication techniques have enabled biologically inspired technical systems that mimic many of these remarkable functions. For example, self-cleaning surfaces are based on the super-hydrophobic effect, which causes water droplets to roll off with ease, carrying away dirt and debris. Design of these surfaces is based on the hydrophobic microand nanostructures of a lotus leaf. In this chapter, the most successful strategies are examined, and future research directions, opportunities and outlooks are discussed. As example, the self-cleaning phenomenon and the self-healing of human wound are described in detail.