Stock material or miscellaneous articles – Self-sustaining carbon mass or layer with impregnant or...
Reexamination Certificate
2001-08-14
2003-04-29
Turner, Archene (Department: 1775)
Stock material or miscellaneous articles
Self-sustaining carbon mass or layer with impregnant or...
Reexamination Certificate
active
06555224
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to biocompatible carbonaceous films for applications including medical implantation and to a method for fabricating the films on a substrate surface.
2. Prior Art
Elemental carbon occurs naturally in two widely known allotropic forms: diamond and graphite, each of which exist in more than one polymorphic-modification. Diamond is a 3-dimensional spatial polymer of tetrahedral carbon in which every carbon atom is bonded to four other carbon atoms by four identical bonds, each 1.54 Å, long. Diamond, which is a dielectric, has a minimal structural unit consisting of a tetrahedron, with carbon atoms occupying positions in each of the tetrahedron's corners and at the center of the tetrahedron.
Graphite consists of one or more 2-dimensional (planar) polymer sheets of trigonal carbon wherein the polymeric sheets form parallel layers. Each carbon atom is bonded to three other carbon atoms with three identical bonds evenly distributed in a plane, each bond being 1.42 Å long. The identical overlying graphite layers are oriented parallel to each other aid are located at a distance of 3.35 Å from each other. Graphite is a conductor of electric current. The 6-carbon benzene ring is the basic structural unit of graphite.
Carbyne is the third known allotropic form of polymeric carbon. The structure of carbyne is the most similar to the structure of Tetracarbon™, the polymeric form of carbon referred to hereinafter as Tetracarbon, which comprises the subject matter of the present invention and is defined. Carbyne is a semiconductor formed from linear polymeric carbon. A straight carbon chain is the basic structural element within a carbyne layer in which every carbon atom is bonded to two neighbors with two equal bonds, wherein each bond is between 1.19-1.38 Å long and the distance between carbon chains is 2.97 Å. A minimal structural unit from which a carbyne crystal can be assembled is a hexagonal prism. Bent chains are located in the corners of the hexagon. Bendings divide the prism into two parts. A straight chain is located in the center of the lower part with a comparable chain being absent in the upper part. Admixture of hetero (non-carbon) atoms may result in such hetero atoms occupying this vacancy. Carbyne was obtained for the first time in 1969 by means of oxidizing polydehydrocondensation of acetylene. Carbyne forms a sheet-like microcystal consisting of a plurality of regularly shifted chemically bonded A-B-A-B . . . layers. Each A layer comprising the microcrystal consists of densely packed carbon chains oriented perpendicular to the plane of the layer and sandwiched between two B layers. A and B layers are regularly shifted relative to each other and chemically bonded to adjacent layers. In each B layer there is a regular grating of chain vacancies. At present, no carbyne crystals are known having a size greater than 1 &mgr;m (Bulletin of the Russian Academy of Science. Physics, 1993, vol. 3, p. 450).
In addition to the pure crystalline allotropic forms of carbon described above, there are a number of intermediate transitional forms such as pyrolytic carbon and glassy carbon. Pyrolytic carbon is a synthetic high-density carbon polymeric with turbostratic structure and composed of either pure or silicon-alloyed carbon microcrystals. These properties distinguish pyrolytic carbon from other polymeric carbon materials such as graphite, diamond and glassy carbon. Short range order in a pyrolytic carbon film which presents a turbostratic structure wherein the carbon chains are in a plane parallel to the plane of the film and is similar to that of graphite; the basic structural unit being 6-carbon slightly-deformed benzene rings. Pyrolysis of a gaseous hydrocarbon is employed for depositing pyrolytic carbon upon a substrate surface. The high temperature required for pyrolytic deposition limits the choice of substrate to materials to those which are stable at high temperatures such as ceramics and low-porosity graphite. In addition, a substrate composed of a brittle material such as graphite must first be mechanically shaped prior to coating. Due to the extreme hardness of pyrolytic carbon, it can only be worked and polished with diamond tools and pastes so that only relatively simple shapes are suitable for graphite substrates.
Vapor deposition has been used to transfer carbon atoms from a turbostratic carbon target to a substrate such as the surface of an implantable prosthesis. By appropriately regulating the conditions under which carbon deposition takes place, it is possible to hold the temperature of the substrate below a predetermined limit so as to minimize or prevent altering the substrate's physical characteristics. Vapor deposition allows carbon to be deposited in a thin film upon a substrate surface, the film forming a coating which retains the turbostratic structure and high-density characteristic of pyrolytic carbon.
Representative patents and author's certificates describing various prior art carbon coatings, including turbostratic coatings, are presented below in Table I.
TABLE 1
Country
Number
Title
USSR
a.c. 1837620
The method of plasma-spraying of
bioactive coatings
a.c. 165628
The method of manufacturing of
free nickel films
a.c. 646578
The method of manufacturing of
thin films
a/c. 1163656
The method of plasma reactive
spraying of films in
vacuum
a.c. 1405361
The appliance for ion-plasma
processing of substrates
in vacuum
a.c. 1750270
The method of manufacturing of
films and the
appliance for its realization
a.c. 1710596
The method of carbon-based
films manufacturing
a.c. 1710596
Pulse generator of carbon plasma
a.c. 1809840
The appliance for thin films
deposition in vacuum
a.c. 336981
The appliance for deposition
of films by means of
cathode spraying
a.c. 603701
The appliance for manufacturing
of metal, semiconductor, and
dielectric films, in
particular, of the artificial
diamond coatings by the method of
cathode spraying
USA
patent 5270077
The method of chemical
deposition of plane diamond
film from vapor phase
patent 5133845
The method of prostheses
manufacturing from polymer
materials with biocompatible
carbon coating
patent 5073241
The method of formation of
carbon films and the
appliance for its realization
patent 5073241
The method of formation
of carbon films
patent 5078837
The method of ion deposition
of coating and the
appliance for its realization
patent 4981568
The method of manufacturing of
diamond films of high
purity at low temperatures
and the appliance for its
realization
France
patent 2675517
The method of deposition of
diamond-like layer and an
object covered with such layer
Japan
patent 5-26867
The method of manufacturing
of hard carbon film
patent 5-10426
Hard carbon film
patent 5-10425
The method of manufacturing
of thin carbon film
patent 5-40825
The method of formation
of hard carbon film
patent 5-42506
The device for vacuum
spraying of films
patent 5-43783
The device for deposition
of film coating
patent 3-177567
The appliance for vacuum
spraying of films
patent 3-15846
The method of formation
of carbon coating with
diamond-like structure
patent 3-6223
The method and appliance
for formation of carbon
coating transparent for
infrared beams
PCT
2/09715
The method of plasma
spraying of biologically
active coatings on implants
European
0467043
Diamond film without a
substrate, the method and
appliance for its manufacturing
0474369
Coating made of diamond-
like carbon
0500359
Carbon with graphite
structure its interpolation
derivatives and the
methods of their production
0474369
Coating made of diamond-
like carbon
0420781
The method of manufacturing
of a carbon-based
material
A method for manufacturing a polymeric prosthesis having a biocompatible carbon coating is shown in U.S. Pat. No. 5,133,845. The biocompatible carbon coating is deposited on the substrate surface by means of triode cathode spraying. Carbon is sprayed at low temperature at a pressure ranging from 6×10
−4
−6−10
−3
mbar (6&tim
Adamyan Arnold A.
Babaev Vladimir G.
Guseva Malvina B.
Lavygin Igor A.
Novikov Nikolay D.
Morrison & Foerster / LLP
Tetra Consult, LTD
Turner Archene
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