Pinned, driven and confined colloidal supercooled liquids and glasses

Abstract

In Nature, disorder is more prevalent than order. In the realm of condensed matter, the most common form of disorder we encounter is structural disorder. The epitome of structural disorder is a glass, although crystals also possess some degree of disorder in the form of point defects, dislocations and grain boundaries. In crystals, however, scientists have developed methods to intelligently utilize these imperfections to enhance the functionality of materials. One such striking example is the development of super plastic materials (Nieh et al. 2005). These materials are achieved by engineering the architecture of grain boundaries, thin disordered interfaces that separate crystallites of different orientations in a polycrystal. The characteristic attributes of any material stem from its structure. For instance in the context of crystallization, at high temperature the system is a fluid and does not posses any long-range order. However, once it crystallizes, the onset of long range order leads to the development of rigidity. Further, the degree of disorder dictates the mechanical properties of crystals. But as always, Nature surprises us by providing exceptions to a general premise. One such popular example of matter is glass which possess a liquid like structure but is rigid like a crystal. Despite decades of research very little is known about glasses, how they form and what gives rise to rigidity. Numerous theories have been formulated to understand amorphous solids. In this process, many new concepts arose which have significantly contributed to other fields like protein folding (Bryngelson & Wolynes 1987) and computer science (Kirkpatrick et al. 1983) as well. However, the lack of understanding of glasses did not hinder their utility. About 500 years ago, it was discovered that glasses offer useful properties like high wear resistance, high fracture toughness, high porosity and many more. Amorphous solids are therefore used routinely for numerous applications ranging from window panes to artificial implants .