1 Improving bioactivity of PEEK composite polymer for bone application Bankole I. Oladapo * , S. Abolfazl Zahedi School of Engineering and Sustainable Development, De Montfort University, Leicester, UK *Corresponding author: E-mail: bankolyable01@gmail.com Abstract Polyether ether ketone (PEEK) is a promising biomaterial to replace traditional metals or ceramic components for biomedical mimic the bone tissue. However, PEEK has many challenges to feed into 3D printing fused deposition melting (FDM) machine due to its high melting temperature and high viscosity, the main weakness to use in medical application is bioactivity and cell attachment. In this research, biomaterials such as calcium hydroxyapatite (cHAp) and reduced graphene oxide (rGO) is used to combine with PEEK to make a composite material to improve interfaces biocompatibility. The FDM method is applied to print PEEK/rGO/cHAp lattice structures. The effect of nanoparticle on the biocompatibility of the surface newly manufactured composite (PEEK/cHAp/rGO) are thoroughly investigated. Surface treatment with the addition of rGO and cHAp are used to accelerate the biological activity of recombinant surface coating with improved mechanical and biological behaviour for bone grafting. The PEEK/rGO/cHAp composite characteristics are investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and mechanical tests. The result is shown that the composite with the highest ratio of rGO of 5% has more biocompatibility and mechanical strength. The Young modulus and bulk modulus of PEEK increase exponentially with the increase of rGO/cHAp from 3.85 GPa to 54.27 GPa, 25% of 5 wt% addition of rGO. Furthermore, PEEK/cHAp induces apatite formation after several days of immersion in body fluids simulator Dulbecco's Modified Eagle Medium (DMEM) which contains the ions in body fluid and nutrient agar solution (NAS) to determine their biological viability. The In vivo experimental results are shown that cell aggregation and biological activity in the proposed composite (PEEK/rGO/cHAp) is higher than pure PEEK. The one tested with NAS shows more cell growth compared to DMEM. Keywords: PEEK; cHAp; rGO; composite; 3D printing; bone implant 1. Introduction The biocompatible materials have significant advantages to expose the human body [1-3]. There is no report in the litreture of the significant damage during contact of biocompatable structures with the human body. One of the primary benefits of biomaterials is to fabricate bone scaffolds. The biomaterial used remains connected with the bone structure, usually under mechanical stress, to assist in regeneration bone growth. Thus, when biomaterials products come into contact with the human body, they are called implants [4-6]. The artifitual implants requires considering different material properties, such as biocompatibility, and acceptable biological response. Mechanical characteristics often have to be dependent on automatic charges. The thermal properties must not be separated significantly between the thermal expansion and the human body to avoid painful patient dimension changes [7-9]. Metallic materials, particularly steel, titanium alloys, cobalt chrome alloys have excellent mechanical properties under mechnical loading conditions. However, some complications have been observed using these