Study Group report
This is the final report on the modelling of spider silk spinning, carried out at ESGI46 on behalf of Spinox.

Report authors:
Paul Dellar (University of Oxford)
David Allwright (Industrial Mathematics KTN)

Introduction
The report raises several modelling questions about the rheology of the dope and gel phases, the kinetics of the phase transition, and the reabsorption of water inside the spider. The specific points addressed in the report are

• Spiders work in a certain regime of parameters, notably channel shape, applied tension, and wall permeability, such that the detachment point is inside the spider. The main conclusion is that the spider’s converging channel is probably crucial, both to provide a form drag to restrain the dope, and to allow internal adjustment to an imposed tension or extrusion rate by moving the location, and hence the cross-section, of the detachment point. In a rig without a correctly designed converging channel, the flow can too easily become a plug flow, with the dope just sliding down the middle, lubricated by wall layers in this extremely shear-thinning material, and the phase transition not properly completed.
• Spinox need to make their machine work in the same regime.
• It is possible to identify this regime more precisely, and in particular investigate the water layer close to the detachment point to refine the very crude zero-pressure assumption above, but this would require further resources.

Download 'Silk.pdf' (90 Kb).