Fruit walls as well as nut and seed shells typically perform a multitude of functions. One of the biologically most important functions consists in the direct or indirect protection of the seeds from mechanical damage or other negative environmental influences. This qualifies such biological structures as role models for the development of new materials and components that protect commodities and/or persons from damage caused for example by impacts due to rough handling or crashes. We were able to show how the mechanical properties of metal foam based components can be improved by altering their structure on various hierarchical levels inspired by features and principles important for the impact and/or puncture resistance of the biological role models, rather than by tuning the properties of the bulk material. For this various investigation methods have been established which combine mechanical testing with different imaging methods, as well as with in situ and ex situ mechanical testing methods. Different structural hierarchies especially important for the mechanical deformation and failure behaviour of the biological role models, pomelo fruit (Citrus maxima) and Macadamia integrifolia, were identified. They were abstracted and transferred into corresponding structural principles and thus hierarchically structured bio-inspired metal foams have been designed. A production route for metal based bio-inspired structures by investment casting was successfully established. This allows the production of complex and reliable structures, by implementing and combining different hierarchical structural elements found in the biological concept generators, such as strut design and integration of fibres, as well as by minimising casting defects. To evaluate the structural effects, similar investigation methods and mechanical tests were applied to both the biological role models and the metallic foams. As a result an even deeper quantitative understanding of the form-structure-function relationship of the biological concept generators as well as the bio-inspired metal foams was achieved, on deeper hierarchical levels and overarching different levels.

Inorganic scaffolds with high interconnected porosity based on bioactive glasses and ceramics are prime candidates for applications in bone tissue engineering. These materials however exhibit relatively low fracture strength and high brittleness. A simple and effective approach to improve the toughness is to combine the basic scaffold structure with polymer coatings or through the formation of interpenetrating polymer-bioactive ceramic microstructures. The polymeric phase can additionally serve as a carrier for growth factors and therapeutic drugs, thus adding biological functionalities. The present paper reviews the state-of-the art in the field of polymer coated and infiltrated bioactive inorganic scaffolds. Based on the notable combination of bioactivity, improved mechanical properties and drug or growth factor delivery capability, this scaffold type is a candidate for bone and osteochondral regeneration strategies. Remaining challenges for the improvement of the materials are discussed and opportunities to broaden the application potential of this scaffold type are also highlighted.

We synthesized cellulose/gypsum composites in the presence and absence of sodium alginate and investigated the interaction between the composite components as well as the mechanical properties of the final composites. Four different types of cellulose fiber materials were used: cellulose UFC100, cellulose B400, nanofibrillated cellulose, and Lyocell fiber. For all investigated composites the total amount of admixed cellulose was between 1 and 2 wt%, the amount of admixed sodium alginate was 0.5 wt%. We determined the morphology of the composites and observed that the particle and fiber dimensions of the admixed cellulose affect the mode of gypsum–gypsum interlocking and the total porosity of the composites. This in turn had a substantial influence on the mechanical properties of the final composite materials. The addition of sodium alginate resulted in an increase of ultimate strain values. Composites with Lyocell fiber, a synthetic fiber, also had a high Young’s modulus.