Principles for Micro-scale Chemical Process Systems Based on Redox-Active Surfactants

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

ABSTRACT CTS-9911863 Abbott, N./ Graham, Michael G. U. of Wisconsin @ Madison The research described in this proposal consists of a hierarchical set of three broad goals, with each subsequent goal building on the results of the previous goal. The first broad goal is to explore, using both experiment and modeling, the use of redox-active surfactants to promote the controlled, surface-driven motion of liquids on spatial and temporal scales that represent the future of microreactor engineering and micro-scale total analysis systems. The second goal of the proposed research aims to exploit this surface-driven flow (using water-insoluble redox-active surfactants) to accelerate slow rates of mixing that result from diffusive transport of reagents when performing reactions in millimeter-sized droplets of liquids (which presently limits the usefulness of microdroplets as microdroplets as microreactors). It is estimated that gradients in surface tension can induce motion within the microdroplets so as to transport chemical species on time-scales that are at least two to three orders of magnitude faster than diffusive time-scales. The third goal is to combine surface-driven convection (induced by water-soluble redox-active surfactants) and mixing with the capability to reversibly assemble and disassemble micelles formed by the redox-active surfactants within bulk of the microdroplets. It is aimed to demonstrate selective extraction, transportation and deposition of sparingly water-soluble organics within millimeter-sized volumes of liquids in ways that may find use, for example, in micro-scale separations processes and total analysis systems. Through the above three goals, it is sought to demonstrate the broad and general applicability of redox-active surfactants to microscale chemical process systems by exploring water-insoluble redox-active surfactants - so as to permit surface in the bulk of the solution - as well as water-soluble redox-active surfactants - so as to permit surface-driven mixing as reversible processes for solubilization (based on reversible assembly and disassembly of micelles) in the bulk of the solution suitable for microscale extraction, separations and analyses.