A microwave processing device/system can create strong temperature gradients in biodegradable polymer material. Novel physical phenomena caused by the heated particles cause local changes in viscosity and flow, leading to high mass transport and current densities in activated polymer matrix materials and to dramatically shorter reaction times and solvent-free reaction conditions. Advancements in the process speed and quality of packaging films in general can be achieved by increasing the polymeric amorphous to crystalline ratio, especially with regard to the claimed methods for manufacturing and sealing biodegradable packaging films. Micron-size particles or nanoparticles in the processed materials can interact with microwaves of different frequencies and intensities to create intentionally varied local material property changes to create an tunable flexible packaging product that is sustainable and “green.” Related systems, apparatus, methods, and/or articles are also described.