Direct ink writing to fabricate porous acetabular cups from titanium alloy

Acetabular cups, which are among the most important implants in total hip arthroplasty, are usually made from titanium alloys with high porosity and adequate mechanical properties. The current three-dimensional (3D) printing approaches to fabricate customized acetabular cups have some inherent disadvantages such as high cost and energy consumption, residual thermal stress, and relatively low efficiency. Thus, in this work, a direct ink writing method was developed to print a cup structure at room temperature, followed by multi-step heat treatment to form microscale porous structure within the acetabular cup. Our method is facilitated by the development of a self-supporting titanium-6 aluminum-4 vanadium (Ti64) ink that is composed of Ti64 particles, bentonite yield-stress additive, ultraviolet curable polymer, and photo-initiator. The effects of Ti64 and bentonite concentrations on the rheological properties and printability of inks were systematically investigated. Moreover, the printing conditions, geometrical limitations, and maximum curing depth were explored. Finally, some complex 3D structures, including lattices with different gap distances, honeycomb with a well-defined shape, and an acetabular cup with uniformly distributed micropores, were successfully printed/fabricated to validate the effectiveness of the proposed method.