Draga Pihler-Puzović is a lecturer in the School of Physics and Astronomy at the University of Manchester. Her research interests are in the fields of Soft Matter Physics, Nonlinear Dynamics and Mechanics of Fluids and Solids.
Draga Pihler-Puzović - Exploring instabilities in slender structure: linking soft microfluidics and soda forming
In this talks we explore two types of buckling in thin cylinder-like structures.
First, we study the effect of inflation on the swelling-induced wrinkling of thin elastic membranes in a set-up that is commonly used to create microchannels in lab-on-chip applications. Using a combination of experiments, mathematical analysis and associated numerical simulations, we demonstrate that the out-of-plane deformation of the inflated membrane and the resulting anisotropic stress lead to two distinct instabilities as the swelling progresses. The membrane first develops small-amplitude wrinkles that retain the cross-channel symmetry. Their wavelength depends on the pressure and is set in a process similar to the axisymmetric buckling of pressurised, uni-axially compressed cylindrical shells. As swelling increases, the membrane undergoes a secondary instability during which the wrinkles coarsen into large-amplitude folds whose morphology can be controlled by the degree of pre-inflation. We elucidate the fundamental mechanisms responsible for this behaviour to explain how inflation can be used as a control mechanism in the manufacture of microchannels.
Next, we study compression of a beverage can, mostly filled with a liquid. When uniaxially compressed empty cylinders buckle, they typically form periodic structures that break both axial and radial symmetry. By contrast, our liquid-filled cylinder buckle axisymmetrically. The resulting ring buckles are localised and appear sequentially, eventually filling the entire can surface. The final periodic pattern has a predictable wavelength that scales with the shell thickness and radius, as observed in the soft microfluidics channels during the initial stages of wrinkling. We characterise the material properties of the cans experimentally in order to model their post-buckling behaviour. The results of our model, which is similar to the 1-D nonlinear Swift-Hohenberg equation, suggest that the sequential appearance of ring buckles occurs via homoclinic snaking. Our system provides a novel experimental demonstration of this mechanism, thereby linking nonlinear dynamics of localised patterns and mechanics of shell buckling.
Published Mar. 20, 2025 9:46 AM
- Last modified Mar. 20, 2025 9:46 AM