Creation of nanoporous tantalum (Ta)-incorporated titanium (Ti) surface onto Ti implants by sputtering of Ta in Ar under extremely high negative substrate biases

The development of new surface modification techniques for improving the biological performances (i.e., osseointegration) and long-term stability of Ti implants is one of the most active research areas in dental and orthopedic implant industries. We herein propose a novel, simple way of creating nanoporous tantalum (Ta)-incorporated titanium (Ti) surfaces onto Ti substrates by applying extremely high negative substrate biases during sputtering of Ta in Ar. In this method, high energetic ions (Ta⁺, Ta²⁺, Ar ⁺) could intensely bombard the Ti substrates, which would cause considerable re-sputtering of the deposited films, creating the nanopores on the surface of the Ti substrates. The highly uniform nanoporous surface with a pore size of ∼40 to 50 nm and a thickness of ∼300 nm could be successfully achieved by applying a negative substrate bias voltage of 800 V, where the Ta was uniformly incorporated in the Ti walls. This nanoporous surface remarkably improved the hydrophilicity of the Ti owing to its highly nanoporous structure. In addition, the attachment, proliferation and differentiation of pre-osteoblasts (MC3T3-E1) were significantly enhanced, which was attributed to the nano-topographic feature and large surface area of the nanoporous surface.