Shell buckling

We showed that dissolving the solvent enclosed within a silica/PDMS colloidal porous shell causes it to deform. This phenomenon can be interpreted in terms of equivalent external pressure due to capillary forces acting on the shell, just like when the solvent enclosed in a porous shell evaporates. We model these phenomenons in the framework of thin shell elasticity, by decreasing the inner volume of an initially spherical surface. The collapsed shapes are scale-free, depending mainly on the ratio between the thickness and the radius of the shell. Our results are then applicable to other systems such as spherical containers under hydrostatic pressure, deflating soccer balls, vesicles under osmotic stress, pollen, red blood cells and virus capsids. Buckle up!	Viscous-core (very) elastic shell	Somewhat plastic shell buckling
		Buckling of a chocolated convex dome (recipe)





Simulations (with Surface Evolver) of surfaces with bending and in-plane stretch energy provide a phase diagram in the relative volume variation / relative thickness space.	Number W of wrinkles at autocontact (relative volume variation ΔV/V~1) as a function of the relative shell thickness d/R. The power-law in (d/R)-1/2 (continuous line) is compatible with W wrinkles of caracteristic size √(dR) on an equator of length proportional to R.	Colloidal shells (diameter 3-5 microns) deformed by evaporation (top), or by dissolution of the inner solvent (bottom), with corresponding numerical shapes.


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