Apparatus and method for intraluminal polymer deposition
Methods and apparatus for applying a coating to an interior surface surrounding a passage of an article. A plasma is generated from a process gas inside the passage of the article, and the coating is deposited from the plasma on the interior surface. The article may optionally be placed inside of a passage of a conductive conduit. Either the article or the conductive conduit is coupled with a radio-frequency generator for generating the plasma inside the passage of the article.
1. A method of applying a coating to a plurality of articles, each article having a first end and a second end opposed to the first end, a passage, an interior surface surrounding the passage, and an exterior surface, the method comprising:
placing the plurality of articles inside a plurality of conductive conduits, each conductive conduit having two opposing ends, a passage, and an interior surface that surrounds the passage such that, at least one of the first end and the second end of the each article is within the two opposing ends of one of the plurality of conductive conduits, and a gap is formed between the interior surface of each conductive conduit and the exterior surface of each respective article;
generating a plasma discharge from a process gas inside the passage of each article when the article is inside the passage of one of the plurality of conductive conduits;
preventing a plasma discharge in each gap between the interior surface of each conductive conduit and the exterior surface of each article; and
depositing the coating from the plasma discharge on the interior surface of each of the plurality of articles.
2. The method of claim 1 wherein generating the plasma discharge inside the passage of each article comprises:
supplying the process gas to the passage of each article at a total pressure within the passage including a partial pressure of an inert gas and a partial pressure of a precursor monomer.
3. The method of claim 2 wherein the precursor monomer is selected from the group consisting of tetramethylcyclotetrasiloxane, hexamethyldisiloxane, and 1,1 ,3,3-tetramethyldisiloxane (tDMSO).
4. The method of claim 2 wherein each conductive conduit is coupled with a power supply, and generating the plasma inside the passage of each article comprises:
supplying radio frequency power from the power supply to each conductive conduit with a pulsing frequency and a duty cycle.
5. The method of claim 4 wherein the duty cycle includes power portions and non-powered portions, and the method further comprises replenishing the process gas within the passage of each article by inward gas flow from opposite ends of the article during non-powered portions of the duty cycle.
6. The method of claim 2 further comprising:
elevating the total pressure of the process gas to support the plasma discharge inside the passage of each article by selecting the partial pressure of the inert gas.
7. The method of claim 2 further comprising: depositing the coating at a uniform thickness between first and second ends of each article by selecting the partial pressure of the precursor monomer.
8. The method of claim 7 further comprising:
elevating the total pressure of the process gas to support the plasma discharge inside the passage of each article by selecting the partial pressure of the inert gas.
9. The method of claim 2 further comprising:
orienting the passage of each conductive conduit and the passage of each article parallel to a direction of flow of the process gas inside a process chamber.
10. The method of claim 1 , wherein the step of placing the plurality of articles inside of the plurality of conductive conduits comprises:
placing one of the plurality of articles inside a respective one of the plurality of conductive conduits.