Direct force producing uniform ultra-thin chitosan films by atomic force microscopy

Biopolymer chitosan plays an important role in functional nanomaterials, tissue engineering and other biological applications. Chitosan thin films have also been involved in many optical phenomena in living organisms, which potentially allows the use of chitosan for optical applications. However, it is rather difficult to produce uniform thin chitosan films because of its intrinsic viscoelasticity. Here we report the fabrication of uniform ultra-thin chitosan films with a thickness of several nanometres using a two-step physical approach with the help of spin coating and mechanical manipulation.