Inspiration versus duplication with biomolecular fibrous materials: learning nature's lessons without copying nature's limitations

Nature offers useful lessons on how fibres with controlled properties can be produced from sustainable starting materials under environmentally friendly conditions. As we begin to learn these lessons, the advantages that they offer have to be weighed against Nature's limitations: the same molecular features that make biomolecular fibres initially processable in water are also reflected in the fibres having water-sensitive properties, which may not be attractive in an engineering material. Particular attention is given to recent findings that the short-term impressive tensile properties of spider dragline silk as recorded in conventional tests performed at constant strain rate are compromised by creep and stress relaxation, especially in humid environments. Some practical steps towards applying Nature's lessons while addressing the constraints of these lessons are suggested.