Spider silk consistent and intrinsically safe nanotechnologies

The threads produced by spiders show huge diversity and various combinations of properties making them a fantastic materials group. With up to seven different spinnerets, many spiders are capable of producing threads with the most varied properties: for capture (extensibility, tackiness), conservation of prey, self-protection (defensibility), and as an aid in movement, etc. (see Fig. 50). A glance at the molecular structure of the silk threads reveals how spiders have "nanotechnically" managed to integrate ductility (stretchability) and tensile strength in order to successfully capture their prey.

Fig. 50. Spider silk110
Fig. 51. Molecular structure of spider silk111

Of interest is the extremely limited number of substances utilized (carbon, oxygen, hydrogen, nitrogen, and amino acid remnants). Just as fascinating is the disposal of no longer needed threads, which are re-consumed by the spider as protein-containing nourishment. The properties of spider silk far exceed those of all existing technical materials. The silk of some spiders is twice as resistant to tearing as steel and up to fifty times more elastic than nylon. Spider silk has been intensively studied by researchers around the world for some time, including work carried out for the U.S. Army in the hope of developing better bullet-proof vests and improved parachutes. Three completely different approaches to large-scale production of spider silk are presently being pursued. One strategy is the "milking" of test spiders in the laboratory, resulting in up to 200 meters of spider silk per day. The animals are anesthetized with CO2 and immobilized. Ethically, this may be (with respect to the spiders) a less than ideal solution, but with a view to possible environmental impacts, however, milking is not entirely unreasonable and to some extent comparable to the traditional harvesting of wool or silk from the silkworm. The two other strategies are a chemical approach to synthesizing spider silk and the implantation of a spider silk-coded genes in cultivated bacteria., It is already possible to manufacture small quantities of spider silk with both approaches. Incidentally, the three approaches outlined also demonstrate clearly that on the basis of "bionic" inspirations from nature very different technical implementation strategies

(and the resulting assessments thereof) can be pursued. Learning from nature, the bionic point of origin, is a far from adequate guarantee for an "intrinsically safe environmental technology" (see von Gleich 2001).

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