A COMPUTATIONAL MODEL DEVELOPED TO DEMONSTRATE THAT DURING THE SPIDER SILK SPINNING INTERNAL DIFFUSION GOVERNS WATER REMOVAL – A PROCESS CENTRAL TO THE GENERATION OF SPIDER SILK’S EXCEPTIONAL MECHANICAL PROPERTIES
Nikola Kojić, Aleksandar Kojić, Miloš Kojić (DOI: 10.24874/jsscm.2025.19.01.13)
Abstract
Solvent removal by diffusion from a polymer solution occurs in various technological processes, such dry spinning of synthetic silk-like fibers. There, it is important to determine the diffusion coefficient which is dependent on the solvent concentration, assuming the validity of Fick’s law. In order to prove the internal diffusion within the dope while traveling through the spider canal, we performed the experimental investigation and developed specific finite element models. We first summarize our methodology of the numerical computation of such diffusion coefficient, published in our reference (Kojić et al., 2006). The diffusion coefficient is determined by matching the mass of the solution computed by the finite element (FE) model, and the mass measured using a pan-weighing experiment, in which a small amount of the polymer solution is placed in a pan and allowed to evaporate into the air. The second part of this report, according to our reference (Kojić et al., 2004), is devoted to exploring the process in which a spider generates a fiber with the extraordinary strength of several orders higher than any technologically produced fiber. It was hypothesized that the governing process within the spider canal where the elongation flow of the dope occurs is the radial diffusion of the water with zero concentration at the canal wall. The computational model for the water diffusion from the dope is developed with the corresponding boundary conditions to confirm our hypothesis.
