Back to basics

The researchers have developed a new way of assessing the potential of the raw material – silk ‘dope’ – for producing fibres with the amazing properties of natural silks spun by spiders and silkworms. They found that the starting materials currently being tried, ‘cocktails’ of dissolved silk fibres, do not have the same flow properties as natural silk dope, and so cannot be spun into super-strong filaments.

A report of the research appears in this week’s edition of Polymer. It describes how Chris Holland and Professor Fritz Vollrath, together with Dr Ann Terry and Dr David Porter, from the Oxford Silk Group took unspun natural silk dope and compared it to artificial silk dope under shear forces similar to those encountered in a spider’s spinning duct. They found that natural and artificial dopes had fundamentally different flow properties.

Native silk dope taken straight from the gland can be drawn into strong fibres without chemical assistance – as demonstrated by the old fisherman’s way of drawing the glands of silkworms in order to ‘spin’ his ‘silk cast’ fishing line. Yet the fibres spun from artificial dope material, which have been ‘reconstituted’ by dissolving silk fibres, cannot be spun into any type of serious filament without chemical treatments, and even then these do not approach the strength of natural silk.