Temperature-Sensitive Complex Fluids

University Of Pennsylvania, Philadelphia PA

Investigators

Abstract

****NON-TECHNICAL ABSTRACT**** This experimental program will explore the fundamental properties of complex fluids such as colloidal suspensions, emulsions, polymer and surfactant solutions, liquid crystals, and mixtures thereof. These soft materials find applications in the paint, food science, and cosmetics industries, in the practical control of fluid flow and micro-fluidics, in cell & tissue biology, and in high-technology problems such as photonics, lithography, biochemical sensors which require new approaches to materials design and processing. Specifically, the research will create new materials to elucidate a variety of basic phenomena such as melting, crystallization, jamming, frustration and other classes of self-assembly. Knowledge gained will improve our ability to directly observe and manipulate micro- and nano-particles and, more generally, macromolecules in solution. This research, in turn, offers insight for the practical problems listed above. Technology developed as part of this research has potential economic benefit, e.g. it has led to the formation of two start-up nanotechnology companies as well as a broad collaboration with a much larger company based in PA. The program will also educate a new generation of scientists and engineers about soft materials and about optical techniques; these students and post-docs strengthen the technological infrastructure of the nation. ****TECHNICAL ABSTRACT**** This program proposes experiments on complex fluids to elucidate effects such as melting and self-assembly. Complex fluids are soft materials including colloidal suspensions, emulsions, polymer & surfactant solutions, liquid crystals, and mixtures thereof. These soft materials find applications in a variety of ?everyday products? such as the paint, food and cosmetics; soft materials concepts are also proving to be useful for understanding cell & tissue biology, and for developing high-technology materials in photonics, lithography and biochemical sensing. A unifying feature of the present program is the creation and use of small particles based on temperature-sensitive polymers. These particles swell and contract in response to environmental stimuli such as temperature, and thereby enable experimenters to induce phase transformations that can then be studied in-situ by optical microscopy and scattering techniques. The research will elucidate a wide-range of phenomena including geometric frustration, melting mechanisms in two- and three-dimensions and in few-layer films, jamming, and the chiral instabilities of particles in ?tubes?. The program will train a new generation of scientists and engineers about soft materials, optical microscopy and micromanipulation, and the knowledge gained will teach us to manipulate micro- and nano-particles in solution, thereby offering insight into the practical problems listed above.