Nitinol Endoprosthesis Oxide Removal via Acid Soaking and Sonication
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Solution Overview
Problem
Existing methods for removing non-protective oxides from nitinol endoprostheses, such as stents, often result in the loss of underlying material and do not ensure uniform protective oxide formation, which can compromise biocompatibility and physical properties.
Innovation Solution
A method involving multiple cycles of soaking in nitric acid for greater than one hour and sonicating in deionized water for between 5 minutes to 20 minutes, followed by inspection and potential repetition, to remove non-protective oxides and form a thin, uniform protective oxide layer of 0.3 to 1 micrometer thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If existing methods are used to remove non-protective oxides from nitinol endoprostheses, then oxide removal is achieved, but significant loss of underlying material occurs and uniform protective oxide formation is not ensured
Solution Approach 1:
The patent applies periodic action through multiple cycles of electropolishing followed by controlled oxidation. Each cycle consists of electropolishing to remove non-protective oxide and electrophoretic deposition to form protective oxide. This periodic repetition ensures complete removal of harmful oxides while building up a uniform protective layer, resolving the contradiction between material loss and oxide formation uniformity.
Solution Approach 2:
The patent replaces mechanical oxide removal methods with electrochemical processes. Instead of mechanical abrasion or chemical etching that cause material loss, electropolishing uses electrochemical dissolution to selectively remove oxide while preserving underlying metal. The subsequent electrophoretic deposition uses electrical fields to deposit uniform protective oxide, thereby eliminating the contradiction between oxide removal and material preservation.
2Manufacturing precision
If multiple cycles of electropolishing and electrophoretic deposition are performed, then uniform protective oxide formation is achieved, but processing time increases
Solution Approach 1:
The patent implements continuity of useful action by immediately transitioning from electropolishing to electrophoretic deposition without intermediate handling or drying steps. The electropolishing bath is directly followed by the electrophoretic deposition bath in a continuous multi-bath line, eliminating idle time between operations. This continuous process maintains manufacturing precision while minimizing processing time.
Solution Approach 2:
The patent merges multiple processing functions into an integrated electrochemical treatment line. The electropolishing and electrophoretic deposition processes are combined in sequence within the same processing system, allowing simultaneous optimization of both steps. This merging reduces transfer time and ensures consistent results across multiple cycles, resolving the time-precision contradiction.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively removes non-protective oxides while forming a protective layer that enhances biocompatibility and corrosion resistance without significant loss of underlying material, meeting stringent guidelines for nitinol oxide thickness.
Implementation Method 1
soaking in nitric acid for greater than one hour
Implementation Method 2
sonicating in deionized water for between 5 minutes to 20 minutes
Implementation Method 3
form a protective oxide layer of 0.3 to 1 micrometer thickness
Data Source
Figure 1
Figure 2
Figure 3(A)~3(D)
AI summary
Methods of treating a device such as an endoprostheses or a batch thereof include first soaking the device in nitric acid for greater than 1 hour; after first soaking the device, first sonicating the device in deionized water for between about 5 minutes and about 20 minutes; and after first sonicating the device, repeating, at least once, soaking the device in nitric acid for greater than 1 hour, and, after soaking the device in the nitric acid, sonicating the device in deionized water between about 5 minutes and about 20 minutes. Methods may further include soaking in a mild acid for between about 30 minutes and about 45 minutes. The methods may form a protective oxide having a thickness between about 30 Å and about 100 Å.