- Chemical Engineering
- Hydrodynamics of Spin Coating -- Dr. Higgins is studying the hydrodynamics of spin coating of sol gel systems as a method for depositing optical coatings on large area optics. Often, the spin-coated film is nonuniform, characterized by radial striations that extend from the substrate edge to near the substrate center. Experiments in his laboratory have shown that the radial striations are a result of a convective instability. To understand the dynamics of this instability, a linear stability analysis of the time- dependent solutions to the momentum, mass, and energy equations for spin coating is being undertaken. These results are being used to establish operating conditions for stable coatings.
- Optical Coatings -- Dr. Higgins is also investigating methods for producing hafnium oxide optical coatings by the sol-gel method from organometallic precursors. The parameters that influence the optical properties and coated thickness are being studied. The dispersion of refractive index of the hafnium oxide coatings is determined from ellipsometry, and transmission spectroscopy.
- Flow Separation in Thin Film Coatings -- Techniques from bifurcation theory are used to study the mechanisms that lead to flow separation in thin film coating flows. Boundary integral and/or Finite Element methods are used to verify the predictions from the theory
- Sol-Gel Synthesis of Bioactive Nanoscale Silica Particles -- Microemulsion technology is used to synthesize nanoscale bioactive silica particles (< 50nm) The water pool provides a chemically favorable ”nano-receptacle” for the enzyme or other pH-sensitive biomolecules and allows the hydrolysis/condensation reactions leading to particle growth to occur in the vicinity of the enzyme. Control of these reactions through catalyst concentration, surfactant/water ratio, and alkoxide/water ratio determines the particle structure that is required for encapsulation of the enzyme. FTIR is used to elucidate the importance of hydrolysis kinetics on particle size, shape, and porosity.