Ellipsometric Measurement of Swelling Properties Associated With pH Responsive Hydrogels in Solution

Previous investigations have demonstrated that aqueous solutions containing hydrogels using 2-hydroxyethyl methacrylate (2-HEMA) as one of the monomer components swell reversibly under variable conditions of pH, temperature, and ionic strength, based upon weight gain ratios. A more unique approach will be employed to measure swelling properties associated with pH responsive hydrogels in buffered solutions, namely ellipsometry. Traditionally ellipsometry has been used to measure thickness of materials on a nanoscale dimension under ambient conditions. Finally, more novel approaches of employing hydrogel swelling response properties will be investigated; including response to glucose and enzyme loading schemes. The goal of our project will be to evaluate the feasibility of utilizing ellipsometry as a means to measure swelling properties based upon changes of thickness of very thin film substrates. This method will allow fast, real-time, remote measurements, and will provide information required for extending the usefulness of ellipsometry to measure micro-cantilever (MS) sensing abilities.