Compliant implantable medical devices and methods of making same
View Patent ↗Implantable medical grafts fabricated of metallic or pseudometallic films of biocompatible materials having a plurality of microperforations passing through the film in a pattern that imparts fabric-like qualities to the graft or permits the geometric deformation of the graft. The implantable graft is preferably fabricated by vacuum deposition of metallic and/or pseudometallic materials into either single or multi-layered structures with the plurality of microperforations either being formed during deposition or after deposition by selective removal of sections of the deposited film. The implantable medical grafts are suitable for use as endoluminal or surgical grafts and may be used as vascular grafts, stent-grafts, skin grafts, shunts, bone grafts, surgical patches, non-vascular conduits, valvular leaflets, filters, occlusion membranes, artificial sphincters, tendons and ligaments.
1. A method of fabricating an implantable medical device, comprising the steps of:
a. providing a suitable sacrificial substrate;
b. vacuum depositing at least one of a metallic and pseudometallic biocompatible material onto the sacrificial substrate thereby forming a film of the biocompatible material, wherein the biocompatible material is deposited through a pattern mask such that the formed film includes a plurality of microperforations passing through the film, thereby forming the implantable medical device; and
c. separating the sacrificial substrate from the formed implantable medical device.
2. The method according to claim 1 , wherein the vacuum depositing step further comprises depositing a plurality of film layers to form a multilayer film structure.
3. A method of fabricating a microporous metallic implantable device, comprising the steps of:
a. providing a cylindrical substrate in a hollow cathode magnetron sputtering deposition device;
b. providing a cylindrical target of a nickel-titanium alloy;
c. thermally insulating the cylindrical target from a cooling jacket;
d. evacuating the deposition chamber to vacuum conditions;
e. depositing a metal at a substrate temperature, a target temperature, a gas pressure, and with a negative bias voltage to the substrate to form a deposited film, wherein the metal is deposited through a pattern mask interposed between the substrate and the target, wherein the pattern mask corresponds to a pattern of microperforations such that the deposited film includes a plurality of microperforations passing through the film; and
f. removing the deposited film from the substrate to form the microporous metallic implantable device.
4. The method according to claim 3 , wherein step a. further comprises: mechanically and/or electropolishing the substrate to provide a substantially uniform substrate topography.
5. The method according to claim 3 , wherein step b. further comprises welding a plurality of wires each having a diameter around an outer circumference of the target to provide an equivalent spacing between the target and the cooling jacket.
6. The method according to claim 3 , wherein step b. further comprises interposing a tubular ceramic insulating sleeve between an outer circumference of the cylindrical target and the cooling jacket.
7. The method according to claim 3 , wherein the target temperature is uniformly hot.
8. The method according to claim 3 , wherein the substrate temperature is maintained within the range of 300 and 700 degrees Centigrade.
9. The method according to claim 3 , wherein the negative bias voltage is between 0-1000 volts to the substrate.
10. The method according to claim 3 , wherein the gas pressure is maintained between 0.1 and 40 mTorr.
11. The method according to claim 3 , wherein step e. further comprises depositing the metal in an Argon atmosphere.
12. The method according to claim 3 , wherein the step of removing the deposited film further comprises exposing the substrate and the deposited film to a nitric acid bath for a period of time sufficient to remove the substrate.