MEMS Seminar: Adsorption at Confined Interfaces

Material at interfaces has different properties than bulk solutions; here we are concerned with the properties of materials that are in the thin film between two interfaces. The properties of such confined material are affected by fields extending from two boundaries and thus are different than material near one interface. These altered properties are important in determining the stability of colloid and nanoparticle suspensions, wetting films, adsorption in confined spaces, and in the fabrication and application of nanoscale devices. Our interest is in adsorption, which affects many of these applications: there is a multitude of applications where surfactants, polymers, ions, etc. are adsorbed to effect changes in thin films, for example, to alter the stability of colloidal particles.

We describe measurements of adsorption between two flat plates when the plates are separated by 0 - 65 nm for two examples (1) depletion of a simple ion in dilute solution and (2) adsorption in very concentrated salt solutions. These measurements have been made possible by our development of a technique to measure adsorption in a crack formed by bonding an oxidized-silicon wafer to a glass wafer. Measurement of film thickness is achieved by using optical interference. The adsorbed amount at each film thickness is measured from the fluorescence emission of a dye, after accounting for the optical interference.

Lunch will be served at 11:30 am.

Hosted by Dr. Stefan Zauscher.