Self-Assembly of Levitating Water Droplets over Polymer Solutions for Fabrication of Microporous Structures

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The Condensed Matter Physics Program in the Division of Materials Research supports Professor Mohan Srinivasarao at Georgia Institute of Technology to create well-ordered porous polymeric structures via a simple and elegant way without using slow or costly fabrication processes. When a polymer in a volatile solvent is evaporated, it results in cooling of the solution. Water from the atmosphere then condenses on the cold surface of the polymer solution. The self-assembly and subsequent crystallization of water droplets produce an ordered array of two- and three-dimensionally (2D and 3D) packed holes in the polymer film. Water droplets condensing on a cold solid surface is seen in a variety of situations in everyday life. Common examples of this phenomenon include dew formation on leaves early in the morning, fogging of eyeglasses when one enters a cold room, water condensing on the lids of coffee cups from Starbucks, and breathing on glass as one polishes it. This research examines the phenomenon of "breath figures" - the condensation on a polymer surface - and paves a new way to construct macroscopic 3-dimensional porous structures from a variety of polymers in a very short time. The fundamental knowledge gained from this study may impact ultrasmall volume reactors, diffraction gratings, and to cell growth scaffolds. In addition, this project provides training of undergraduate and graduate students with emphasis on its integration with this research. The project also develops outreach programs connected to Lawrence Hall of Science to communicate the value of this research to the public.With this support from Condensed Matter Physics Program in the Division of Materials, Professor Srinivasarao’s research team elucidates the mechanism behind the phenomenon of moisture condensing on a cold surface called breath figures. Although it is known that macroporous polymers could be used as a template to make ceramic and metallic structures with 2-dimensional pores, the mechanism by which the structures form is far from understood. This research studies the physics and physical chemistry of the phenomena involved in the self-assembly of breath figures. The team investigates key processes such as nucleation and growth, ordering dynamics, noncoalescence, surface tension driven instabilities, packing of spheres, and heat/mass transport, and wetting. These measurements are carried out by using high-speed video microscopy. Understanding the formation kinetics/mechanism of breath figures and the optical/physical properties of the resulting 3-dimensional structures may lead to a simple and effective way to rapidly create ordered, macroporous structures from a variety of polymers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.