Scientists from the Lebedev Physical Institute, together with the Belgorod colleagues have proposed a new method for surface modification of titanium, giving it the unique optical and mechanical properties, as well as improving the biocompatibility of the sample. Implants made of nanocrystalline titanium with a biocompatible coating are currently in preclinical testing.
Proposed modifications of the method consists of irradiating the surface of the nanocrystalline titanium femtosecond laser, causing it to appear with characteristic periodic structures and multi-submicron to micron size. As a result of studies, it was found that by varying the emission parameters, it is possible to control the sizes occurring structures, and hence the properties of the material, while maintaining the unique mechanical properties of nanocrystalline material state.
"We came to this theme by exploring our colleagues from the Center for Nanostructured Materials and Nanotechnology of the Belgorod State University, who led the Doctor of Physical and Mathematical Sciences, Professor Yuri Kolobov Romanovich. His staff has been successfully engaged in the creation, study and implementation of nanocrystalline titanium, which is attractive, first of all, its unique mechanical properties — high strength and superplastichnostyu. However, for biomedical applications — in particular, for modifying the surface of titanium implants — nano required (that enhance biocompatibility) and the surface microtexture, which create a "incubator" for osteoblast cells"- Says Andrew, son of John, Head of the Laboratory of Gas Lasers Division of Quantum Radiophysics LPI.
Write a surface nano-and microtexture while maintaining the inherent structure of nanocrystalline material initially with conventional treatment are very difficult. For example, plasma etching or annealing warm up pretty thick surface layer — the nanocrystals are sintered or fused, there microcrystals, which greatly affects the mechanical properties of titanium. And when exposed to ultra-short laser pulses due to their high capacity to high temperatures very quickly heats only a thin surface layer. After that, the energy begins to spread deep into the surface temperature drops, and no undesirable sintering of nanocrystals is not happening
The resulting nanostructured surface is a well-defined one-dimensional lattice with a characteristic step in the 70-600 nm. Thus, when the density of the laser radiation 17 mJ / s2 a series of pulses 500 forms on the surface a titanium target sequence narrow grooves (thickness: about 100 nm), spaced apart by an average of 400 nm. The emergence of such quasi-periodic structures scientists explain the interference of the electric fields of the incident radiation from the surface electromagnetic waves that excite the surface of femtosecond laser pulses.
By increasing the energy density increases and the width of the grooves of the relief grating is well-defined and almost harmonic However, with further increase of the laser energy density, this grill almost disappears, and the surface gradually appear expressed microcones embryos. (Prolonged or high-intensity exposure the entire surface with an array of microcones, giving the surface of virtually 100%-ing the absorption capacity). Thus, by changing various parameters of the laser radiation — the energy density, the length of the radiation pulse duration and the number of — in the proposed method it is possible to control the morphology of the surface of the nanocrystalline titanium.
Figure 1. Image of the titanium surface with nanometer quasiperiodically relief
obtained by scanning electron microscopy
Figure 2. Image of the surface of titanium coated with micrometer cones
with nanometer quasi-periodic relief
obtained by scanning electron microscopy
The surface of the nanocrystalline titanium nano-and stores topographical increased strength and ductility, are typical of the bulk material, and acquires high hydrophilicity necessary for its biocompatibility. Accordingly, such a surface morphology of titanium makes an ideal candidate for the development of new implants, which are undergoing preclinical trials in cancer institute named after PA Herzen. Says Sergei Kudryashov,
Senior Research Laboratory sotrdunik gas gas lasers LPI
"Over the past five years out dozens of works on the application of nanocrystalline titanium. From it you can make a plate for the skull, dental implants, different core design. Another very interesting application — it microsurgical instruments with cutting edges of nanotitan. Production of nanocrystalline titanium are now appearing all over the world. In Russia in this area there are benefits associated with a well-developed production of titanium. The advantage of this method is cheaper than current production technology and high-tech processing of nanocrystalline titanium. To provide leadership in this area, we can only establish such a treatment."
These interdisciplinary materials research, except employees of the laboratory gas lasers OKRF LPI — Andrew Ioannina, Sergei Kudryashov, Dmitry Zayarnaya, participate and graduate students — Sergey Makarov, Paul Saltuganov and members of other academic institutions — GPI, Ishmael, ICP RAS and others.
Petrov, ANI "LPI-Inform"