291644 Optical Method for Measuring Diffusivity Through Hydrogel-Filled Microfluidic Capillaries

Monday, October 29, 2012
Hall B (Convention Center )
Amanda Card1, Thomas Kelly1, Andrea Kadilak1 and Leslie M. Shor2, (1)Department of Chemical, Materials, and Biomolecular Engineering, University of Connecticut, Storrs, CT, (2)Department of Chemical, Materials and Biomolecular Engineering, University of Connecticut, Storrs, CT

Hydrogels are highly crossed-linked networks of hydrophilic polymers that have the capacity to absorb large quantities of water while maintaining their structure.  Hydrogels are widely used in the food, pharmaceutical, and personal care industries. Diffusion coefficients through hydrogels are a function of solute and hydrogel properties. Experimental methods used to measure diffusivities for more rigid materials, such as polymer membranes, have been previously developed and are widely used. However, these methodologies are not conducive to measuring diffusive properties of solutes through soft hydrogels. Here we describe a high-throughput optical method to determine molecular diffusivities of solutes through weakly cross-linked hydrogels. Microfluidic devices offer reproducible geometries and are capable of creating highly resolved concentration gradients that are also easily quantified using simple optical methods. Here we describe a microfluidic array of flow cells comprised of narrow capillaries of various widths, lengths and configurations. The microfluidic capillary array can be used to characterize solute diffusion through a broad range of materials ranging from rigid, highly cross-linked hydrogels to fluid, non-viscous liquids. We validated this method by measuring the diffusivities of well-characterized molecular dyes, including fluorescein and xylene cyanol, and select antibiotics through agarose hydrogels of varying cross-link densities. Better understanding solute diffusion through hydrogels will lead to improved technologies and processes for the many industries that use these materials.

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