Printing orientation defines anisotropic mechanical properties in additive manufacturing of upper limb prosthetics

Additive manufacturing (AM) technologies are potential future-shaping solutions throughout many special applications in medicine. The mechanical behaviour of the related materials has not yet been fully explored. Here we compared five different industrial quality 3D printing materials produced using various AM processes that can be potentially used in limb-prosthetic development. We focused on the anisotropy of the mechanical and structural properties of these materials by using static and dynamic testing methods and electron microscopy imaging. Both static and dynamic experiments confirmed that amongst the three investigated directions (X, Y and Z), the Z orientation demonstrated, with the exception of polyamide test specimens, the lowest resistance against mechanical forces. Electron microscopy images revealed that greater mechanical stability appeared presumably due to the lengthier cooling time of the individual printed lines. Varying the printing resolution we showed how greater mechanical stability could be achieved, and concluded that special care should be taken when designing the AM processes intended for the fabrication of objects in support of medical applications. Often, the use of poor resolution in respect to quality of printing is desirable and can provide better solutions for actual purposes. These results provide important guidelines in the planning, manufacturing and implementation of higher developed, well-constructed assistive devices.