The study of instabilities is at the heart of classical and continuum mechanics, and continues to be a source of inspiration in the design of functional materials and structures. Many objects of study in soft-matter physics are susceptible to instabilities under generic conditions and weak perturbations, so that the onset of these instabilities and the behavior of the object after the instability are of the utmost importance in formulating theory and in creating devices. An analogous phenomenon in statistical mechanics is the concept of a phase transition. Both phase transitions and mechanical instabilities can be described as qualitative changes in a system as control parameters are manipulated, and in both phenomena there exist classifications of the qualitative changes that occur. In fact, there is a unifying mathematical framework underlying both phenomena. The two also occur simultaneously in many modern soft-matter systems that couple objects of statistical mechanics with objects of continuum mechanics, such as liquid crystals. These macroscopic structures with often-nontrivial microscopic degrees of freedom allow for extremely precise tuning of material parameters and behaviors, with pre-programmed and tunable instabilities coming to the fore in recent years as design mechanisms rather than design flaws. In this work we consider some particular examples of this school of thought --- buckling and wrinkling instabilities of liquid-crystal elastomer plates which can be tuned by manipulating the internal degrees of freedom, and also fluid instabilities of both Newtonian and non-Newtonian type whose onset can be triggered, delayed or suppressed entirely by particular types of external forces. We provide a description of the mechanism of instability tuning and set these phenomena in a broader framework.
Krieger, Madison Ski,
"Tunable Instabilities in Soft Matter"
(2016).
Fluid, Thermal, and Chemical Processes Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://doi.org/10.7301/Z0KW5DGF
