Soft Matter 'Odes': from the life and death of viscoelastic jets to the structural color of jeweled beetles

Soft Matter 'Odes': from the life and death of viscoelastic jets to the structural color of jeweled beetles

12:15 in the M-Building, room 3201 A, for details see www.softmatter.gatech.edu/baglunch.html

Most industrial and biological materials exist, or are processed, in the form of multicomponent, microstructured fluids, and their ultimate function and use is dependent on the understanding of the optics,...

Date

January 21, 2011 - 7:15am

Location

MSE 3201 A

12:15 in the M-Building, room 3201 A, for details see www.softmatter.gatech.edu/baglunch.html

Most industrial and biological materials exist, or are processed, in the form of multicomponent, microstructured fluids, and their ultimate function and use is dependent on the understanding of the optics, dynamics, elasticity & extensibility and self-assembly (ODES) of the constituent soft or squishy materials. With the guiding idea of designing beautiful and useful patterns, possibly by mimicking nature, I will present two examples of "odes" in soft matter:


   Surface tension driven break-up of cylindrical fluid elements into droplets plays a crucial role in the use or processing of paints, inks, insecticides and pesticides, cosmetics, food, etc, as well as in drop formation during sneezing. The industrial fluids are typically formulated using dilute polymer solutions, and are exposed to a wide range of shear (1 - 106 s-1) and extension rates (in excess of 103 s-1). Since the polymer solutions and the resulting dispersions have low viscosity (~10 mPas) and short relaxation times (


In the second part of my talk, I will proceed to a discussion of the cellular pattern that decorates the exoskeleton of Chrysina Gloriosa. The metallic green beetle that displays circularly polarized iridescence has hexagonal cells (~10 mm each) that coexist with pentagons and hexagons, and we find that the fraction of hexagons decreases with curvature. Each cell consists of nearly concentric, nested arcs that lie on the surface of a shallow cone. We inferred that patterns are structurally and optically analogous to the focal conics domains formed on the free surface of a cholesteric liquid crystal. Perhaps the study of capillary break-up and structural color will allow us to design better light harvesting devices in future, or potentially result in sprayable hair color or paints that display iridescence.