Researcher Nere Garmendia, based in the Basque city of Donostia-San Sebastián, has published a doctoral thesis that may pave the way for the development of implants with impressive lifespans. According to Garmendia, orthopaedic implants could be developed that would last more than 150 years by developing a composite material made from carbon nanotubes, zirconia ceramic and nanoparticles of zirconia.
Garmendia tested the composite in the lab to confirm its durability. The material gets its strength from a matrix of zirconia and carbon nanotubes, which, when fused, improve load transfer and distribution. The carbon nanotubes themselves were coated with nanoparticles of zirconia. For bonding of the two to take place, the nanoparticles had to be heated beyond their boiling point. The procedure enables a sort of “bridge” to be formed between the carbon nanotubes and the zirconia matrix.
Garmendia explained in her thesis that working at a nanometric scale is the key to achieving long-lasting prostheses. In a prior experiment, it was concluded that micrometric zirconia would show considerable signs of ageing after 12 years. But by adding zirconia-coated carbon nanotubes to the material, no signs of ageing were visible in lab testing that simulated normal wear in the body for a period of 150 years. According to the researcher, adding zirconia nanoparticles to the carbon nanotubes facilitates the dispersion of the material and reduces its viscosity. In addition, it helps increase the density of the composite for synterisation—a process often used with ceramics to transform the material from powder to a compact solid.
As Garmendia calculated, if the intention is to obtain the maximum possible density (98%) of the composite material, 1% of its volume must be of coated nanotubes. Finally, the material has to be synterised in argon for one hour at 1300 degrees Celsius.
More information on the research is available from Basque Research.