Chemical Analysis Based on Environmentally Sensitive Hydrogels and Optical Diffraction

Abstract

A new concept for rapid on-line detection of organic compounds is investigated, combining optical diffraction and patterns of environmentally sensitive hydrogels, which are prepared by micromolding in capillaries (MIMIC). Hydrogels respond to varying environmental conditions with changes in volume. Since the intensity distribution of the diffracted light is determined by the form factor of a single scattering element, the volume changes can be detected by Fourier diffraction optics. In order to demonstrate the potential of this concept microscopic diffraction gratings of Polyacrylamide gel were prepared onto a gold surface and exposed to mixtures of water and ethanol vapor of different concentrations. Ethanol can be determined by taking several diffraction spots into account. Compared to macroscopic gels a drastic decrease in response time was observed.