Photolithographic Process for Integration of the Biopolymer Chitosan Into Micro/Nanostructures

This paper describes a novel photolithographic method to fabricate MEMS structures from chitosan, which is a beta-1,4-linked polysaccharide. The biopolymer chitosan is the partially deacetylated product of chitin. Chitin is used in nature as robust bioscaffolds and infrared absorbers. Chitosan has been shown to have similar properties and may additionally form cationic hydrogels. Patterning methods for chitosan in the literature include imprinting, electrodeposition, and mold-casting. These methods have numerous substrate and surface topography limitations and occur in aqueous solutions, which for most hydrogels, are when they are most susceptible to chemical changes. In order to surmount these obstacles, the authors have adopted low-temperature photolithography for the chitosan that uses the following: 1) a polymethyl-methacrylate chemical barrier layer and 2) a dry anisotropic oxygen plasma etch for direct transfer of features-as small as 1 mum.