Researcher(s)
- Stephen Moir, Chemical Engineering, University of Delaware
- Matthew Pitell, Chemical Engineering, University of Delaware
Faculty Mentor(s)
- Eric Furst, Chemical Engineering, University of Delaware
Abstract
Colloidal suspensions are ubiquitous, appearing in industrial applications, as well as in the natural environment. Optical tweezers can be used to investigate the underlying physics of these materials. One difficulty when using optical tweezers is sample preparation. Air bubbles, flow fields, and diffusion timescales can cause experimental difficulties and even failure. In order to solve this issue, double-sided tape was laser-cut and heated. The channel was designed to have as few corners as possible, with rounded edges to reduce flow resistance and pressure drop. Melting the tape creates better adhesion between the coverslip and tape, resulting in decreased nucleation on the tape surface. The result was a channel that was easy to consistently produce in large quantities. The possibility of a reusable channel that liquid can be run through to simulate flow is being explored. With optimized channels, we can investigate the surface chemical response for silica colloids in contact, which is important for bulk rheology. The environmental conditions of salt and pH tune the interaction and aging between silica surfaces. To understand the interactions between particles, it is important to know the surface chemistry of the individual particles. To get a better idea of the surface chemistry of the silica particles, zeta potential measurements can be taken and interpreted. By finding the electrokinetic potential at the slipping plane under different ionic strengths, salt concentrations, and pHs, an understanding of the surface charge can be formed. Since we are dealing with small surface charges, the linearized Grahame equation can be used. We can then relate the surface charge to the bending mechanics and behavior of interactions between silica particles, forming a better surface characterization of silica particles.