These last few decades, the melt extrusion process has gained a great interest from the food industry as well as from the chemical, pharmaceutical and medical industries. As for the 3D printing, it is currently booming. Our work is focused on the ability to insert lipids micro-reservoirs during the extrusion at the interface between two polymers for the elaboration of an advanced and efficiently active delivery scaffold after 3D printing and extraction of one of the polymers. The fundamental aspects are relative to interfacial phenomena and rheology of materials but also to mass transfers through a liquid, a polymer membrane or a polymer matrix. The polymer chemistry is used to stabilize the droplets and to control the encapsulation. The chemical characterization and the microstructural properties of material are studied at each step. This design combines environmentally friendly process and formulation with nontoxic products. A particular attention is given to the selection of available and inexpensive products, of natural origin with biodegradability properties.