Graphene enhanced anti-corrosion and biocompatibility of NiTi alloy

- Graphene film wrapped on the NiTi alloy exhibits good anticorrosion and biocompatibility.
- The supervisory of graphene is its flexibility, which keeps excellent mechanical stability upon deformation.
- The behavior of graphene for inhibiting poisonous Ni ions releasing was explored through theoretical calculation.

Due to their unique shape memory effect and superelasticity, NiTi shape memory alloys have been considered for a wide range of biomedical applications. However, they are still controversial because of the potential toxic, carcinogenic and allergic effects caused by Ni2 + release for a long term use. Wrapping protective layers with good flexibility and biocompatibility is significant for inhibiting the poisonous Ni2 + releasing from NiTi. Here, we report a novel method to protect the NiTi and enhance its biocompatibility by using graphene fabricated via a modified chemical vapour deposition (CVD) technique. The graphene layer not only prevents effectively the leak of Ni2 + but also improves the biocompatibility of NiTi upon deformation. The detailed mechanism for enhancing the anti-corrosion and biocompatibility of NiTi alloy by using graphene is also explored. Compared with traditional surface modification layer, graphene obtained by CVD is chemically inert and highly flexible, possesses both good anti-corrosion and biocompatibility properties, which may improve the surface coatings for NiTi alloys and promote more application of graphene in biomedical materials.

A large sheet of graphene was fabricated by a CVD method, and transferred onto the NiTi shape memory alloy substrate. It is calculated that the significant inhabitation of Ni2 + releasing is kinetically hindered caused by the high energy barrier built upon graphene wrapping even under stain or with Cl−. The graphene film obtained by CVD is chemically inert and highly flexible, which demonstrates a significant reduction of Ni2 + releasing from NiTi and greatly enhances its anti-corrosion ability. Additionally, both blood and tissue cells display a better attachment on the NiTi with graphene manifests the improvement of its biocompatibility.175