Optical Methods to Measure Diffucivity Characteristics of Biocompatible Polymers
Authors:Michael Tran, Zheng Wong
Mentor:Roy McCord, Professor of Physics/Laser Technology, Irvine Valley College
Biocompatible semi-permeable membranes have important application in encapsulation of pancreatic islet tissue as a curative approach for diabetes. Diffusivity is a critical characteristic of encapsulation membranes which need to allow the inflow of smaller nutrient molecules (less than 3kDa) while excluding larger immune response molecules (greater than 200kDa.) A technique to measure diffusivities of bulk membranes that is sensitive to diffusivities less than 10-11 cm2/s is explored. The technique is based on both micro- and macro-optical densitometry to determine degree of absorption of permeant molecules into semi-permeable membrane materials. Analysis is based on a mathematical solution of a Fick’s Law diffusion model for planar slabs. Results are reported for a variety of polymers and alginate.