2) An optimized vascular network coupled with effective surface modifications and coatings to minimize the foreign body response of the device 227 . The functions of the heart and arteries are mechanical rather than chemical, thus an effort to recreate in the systems the forces and stresses produced by the blood flow on the walls of the cardiovascular vessels is mandatory. The blood flow path should reproduce the circular vascular channels geometry, follow natural scaling and branching laws, and exhibit velocities and shear stress in a physiological range.