****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.
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.
The materials we study are called complex fluids. These soft materials find applications in the commercial sector, including companies involved with paint, food science, & cosmetics industries, and in high-tech problems such as photonics, printing & lithography, biochemical sensing, and in design of advanced composites. Knowledge gained in these studies enhance our ability to manipulate macromolecules in solution, and thus provides insight for the many of the practical problems listed above. For example, technology developed as part of this research has led to the formation of two start-up nanotechnology companies and to a major collaboration with a larger chemical company. The program also teaches a new generation of PhD/post-doctoral scientists and engineers about soft materials and optical microscopy & micromanipulation; after finishing work here, these students and post-docs strengthen the technological and economic infrastructure of our nation. This experimental program advanced our understanding of the nature of glassy materials. Experiment from our lab discovered localize vibrational modes in colloidal glasses that showed a propensity to rearrange in response to applied mechanical stress. The work provides important clues about the nature of disordered materials, ranging from glasses to granular matter. The experimental program also advanced our understanding about how colloidal particle shape can influence deposition of material from drying drops. This work holds potential to impact a variety of practical problems which arise in printing, painting, biochemical sensing, and in design of advanced composites. The experiments in both target areas listed above (behavior of disordered matter, shape and evaporative deposition) are of interest in other disciplines besides physics, including chemical engineering, chemistry and materials science & engineering. . Knowledge gained will enhance our ability to manipulate micro-/nano-particles and macromolecules in solution/suspension, and provide insight about how one might make glassy materials more tough. The primary gain from this program comes about because it trains PhD students and post-docs in the science of soft materials and the technology of optical microscopy & micromanipulation; these students and post-docs, in turn, will leave Penn and strengthen the technological infrastructure of our nation. In addition, every year we expose undergraduate students and even high school students to STEM research and careers; these students make up the "pool" for the future US science and engineering workforce.
