Circumferential buckling of a hydrogel tube emptying upon dehydration

A cylindrical hydrogel tube, completely submerged in water, hydrates by swelling and filling its internal cavity. When it comes back into contact with air, it dehydrates: the tube thus expels the solvent through the walls, shrinking. This dehydration process causes a depression in the tube cavity, which can lead to circumferential buckling. Here we study the occurrence of such buckling using a continuous model that combines nonlinear elasticity with Flory-Rehner theory, to take into account both the large deformations and the active behaviour of the hydrogel. In quasi-static approximation, we use the incremental deformation formalism, extended to the chemo-mechanical equations, to determine the threshold value of the enclosed volume at which buckling is triggered. This critical value is found to depend on the shell thickness, chemical potential and constitutive features. The results obtained are in good agreement with the results of the finite element simulations of the complete dynamic problem.

Automated summary

A cylindrical hydrogel tube undergoes hydration and dehydration processes when submerged in water and exposed to air, respectively. The dehydration process leads to circumferential buckling due to the depression in the tube cavity. A continuous model combining nonlinear elasticity with Flory-Rehner theory is used to study this buckling phenomenon and determine the threshold value for buckling. The results obtained from the model are consistent with finite element simulations.