Graduation Year

2008

Document Type

Thesis

Degree

M.S.E.E.

Degree Granting Department

Electrical Engineering

Major Professor

Rudy Schlaf, Ph,D

Committee Member

Andrew Hoff, Ph.D

Committee Member

Jing Wang, Ph.D

Keywords

Airbrush, Roughness, Evanescent, Immunoassay, Residue

Abstract

In this paper, a parametric study of the airbrush deposition technique was investigated for the deposition biomolecular thin films. The airbrush parameters under investigation were intake valve opening, carrier gas pressure, distance between the airbrush and substrate, concentration of solution, vapor pressure of solvent, and hydrophobic/hydrophilic substrate surface. This study was assessed through the characterization of dried droplet residues of Bovine Serum Albumin (BSA) and of complete films of BSA by means of scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was determined that droplet size was mainly affected by carrier gas pressure and vapor pressure. The parameters intake valve opening, distance between the airbrush and substrate, and concentration of solution control the rate of spray, or solution flux, onto the substrate. Solution flux was determined to have the greatest impact on film roughness. This allowed for flexibility in the airbrush deposition technique to produce films with various substrate wetting rates. Low flux films were produced when the droplets dried on the substrate surface before the next droplet arrived. High flux films were generated when droplets on the surface arrive before subsequent droplets are given time to dry. Finally, as an extension of the results of these experiments, a practical application of the airbrush deposition technique was conducted using appropriate deposition parameters. An E. coli wave guide biosensor was produced on a glass substrate. A sandwich immunoassay was used to confirm E. coli capture.

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