| A Soft lithographic patterning technique was used to generate optically active structures, or diffraction gratings, on gelatin films for facile, optical monitoring of dynamic environmental changes, and to assess the effectiveness of imprinting a variety of structures on gelatin, using a PDMS master. Optical monitoring can be a simple alternative to more invasive sensing techniques, and gelatin is well suited for this application due to its biocompatible properties. Imprinting effectiveness was confirmed by several methods, including: generation of optical patterns, analysis of AFM images, and visual inspection of dried film surfaces. Gelatin films were shown to successfully replicate a variety of patterns, and the use of higher temperatures was found to result in a more reliable pattern transfer from PDMS to gelatin. Imprinted diffraction gratings were further used to show a linear relationship between gel water content and percent change in groove spacing, and the ability of gelatin films to retain an imprinted pattern after soaking in water for one hour. A variety of crosslinks were investigated (physical, chemical, and physical-chemical), but films containing both chemical and physical crosslinks were found to be most effective at retaining an imprinted diffraction grating after soaking and re-drying. |
