The state of the art coating

CARBOFILM stems from Sorin's extensive know-how of Pyrolytic Carbon

For over 30 years Pyrolytic Carbon (PyC) has been the material of choice for the components of Mechanical Heart Valves due to the combination of high strength and resistance to fatigue with excellent tissue and blood compatibility.

PyC is a high-density synthetic material with turbostratic structure composed of either pure or silicon alloyed carbon microcrystals.

Since the 60's, Sorin has been one of the pioneers in the production of PyC, and is today the sole company in Europe to own PyC know-how and technology.

The characteristics of all PyC manufacturing processes have so far impeded its more extensive employment due to:

• The extremely high working temperature of the chemical process (over 1200°C) which confines the application to a few types of graphite.
• The hardness of PyC, which prevents the grinding and polishing of complex-shaped components.

In the early 80's Sorin was committed to exploit a new technology, which could extend the excellent biocompatible and haemocompatible characteristics of PyC to all types of substrates, suitable for cardiovascular implantable devices due to their structural characteristics while overcoming intrinsic PyC manufacturing limits.

Sorin Biomedica developed and engineered a unique process for depositing an ultra-thin film of turbostratic carbon, Carbofilm, on all types of substrates, even those heat-sensitive.

CARBOFILM developed and engineered totally in-house.

Carbofilm is a high-density, ultra-thin film of turbostratic carbon that can be deposited on heat-sensitive substrates, such as polymers, polyester fabrics and yarns and metal alloys widely employed in medical devices.

The technique used is a physical vapour deposition (PVD) process where groups of carbon atoms are transferred from a pyrolytic turbostratic carbon target to the substrate to be coated. This process is carried out in high-vacuum conditions which prevent from any chemical reaction.

Unlike other PVD techniques, the Sorin process provides independent control of the deposition rate and the energy associated to the atoms transferred, thus maintaining the temperature within any previously established upper limit. This avoids any changes of the physical characteristics of the substrate, while ensuring excellent adhesion of the film to the substrate.

CARBOFILM is pure carbon.

The Rutherford Backscattering Spectometry (RBS) technique has shown that Carbofilm is pure carbon.

CARBOFILM features a turbostratic structure equivalent to that of PyC.

The nature of chemical bonds between atoms, crystalline structure and crystallite size, are the features that identify PyC from other carbon materials. By means of different measurement techniques (X-ray Diffractometry, Auger Electron Spectroscopy, X-ray Photoemission Spectroscopy), Carbofilm has shown an equivalent turbostratic structure to that of PyC. The cristallite size of Carbofilm is in the range of PyC, and significantly lower than of graphite.

CARBOFILM features high adhesion strength.

The Sorin Quality Control Department submits each lot of Carbofilm coatings to "pull-tests", the so called tests which assess the adhesion strength of the Carbofilm layer to the substrate. The required threshold to overpass is 70 Mpa (700 Kg/cm²).

Carbofilm is about 0.5 µm thin. Such thickness does not change the morphological and physical characteristics of the coated component (polymers, polyester fabrics and yarns, metal alloys). Film continuity is retained even under deformation of the substrate.