Fabrication of Chitosan Bioplastic Diffraction Gratings from Crab Shell Waste Blended with Cornstarch via Soft Lithography

The rising demand in the seafood industry leads to significant waste, which, if not properly disposed of, causes environmental issues. There is a need to bridge the gap between seafood production and waste management by transforming waste into a valuable resource. This study uses various laser sources to produce bioplastic diffraction gratings from seafood waste and evaluate their diffraction performance. It reports the diffraction efficiency at two laser wavelengths for chitosan bioplastic diffraction gratings made from crab shell waste blended with starch. Chitosan was extracted from crab shell waste through four main steps: demineralization, deproteinization, depigmentation, and deacetylation. A chitosan-starch mixture was prepared and then poured into a master mold for elastomer gratings, replicated from a commercial grating. Gratings with groove densities of 600 lines/mm and 1200 lines/mm were successfully produced. Using a He-Ne laser (633 nm) with 0.8 mW power and an Ar+ ion laser (514.5 nm) with 25 mW output power, the diffraction efficiencies of the fabricated bioplastic gratings were measured. Results showed that the measured diffraction angles closely matched theoretical predictions. The diffraction power efficiencies of the bioplastic gratings were comparable to those of polydimethylsiloxane (PDMS) grating replicas. These findings demonstrate the compatibility of a chitosan-starch blend with soft lithography for fabricating diffraction gratings.