Polymer Particle Lubricant for Hermetic Window Sealing
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Solution Overview
Problem
Current window sealing techniques for optical measurement probes face challenges such as temperature and chemical compatibility issues with elastomeric seals, and thermal stress and material limitations with metal seals, particularly in achieving high hermeticity and avoiding contamination in life science applications.
Innovation Solution
A method involving a lubricant composed of polymer particles suspended in a volatile, low viscosity, low surface tension carrier fluid, such as alcohol or cyclohexane, is applied to the window and aperture sidewalls to control friction during pressing, allowing for intimate mechanical contact and filling interstitial voids with residual polymer particles, thereby achieving a hermetic seal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If compression bonding is used to seal the window into the probe body, then hermetic sealing and chemical resistance are improved, but the pressing forces required may damage the window or probe body
Solution Approach 1:
A lubricant composed of metal particles suspended in a volatile carrier fluid is applied to the interface between the window and probe body. The lubricant reduces friction during pressing, enabling hermetic sealing at lower forces that prevent damage. After pressing, the carrier fluid evaporates, leaving metal particles that fill micro-voids and enhance the seal's temperature and chemical resistance.
Solution Approach 2:
The lubricant's physical state changes from a fluid suspension during pressing to a dry particulate coating after evaporation. This parameter change allows the same material to serve dual functions: reducing friction during assembly and providing thermal/chemical resistance in the final sealed configuration.
2Reliability
If higher pressing forces are used to achieve sufficient seal, then hermeticity is improved, but the risk of window fracture or probe body damage increases
Solution Approach 1:
The lubricant acts as an intermediary that reduces direct frictional contact between the window and probe body during pressing. This allows the pressing force to be transmitted more efficiently to create the hermetic seal without being lost to friction, thereby achieving adequate sealing at lower overall forces that prevent window fracture or probe body damage.
Solution Approach 2:
The lubricant is applied beforehand to cushion the pressing operation by reducing friction. This preliminary protective measure ensures that the subsequent pressing force does not exceed the damage threshold of the window or probe body while still achieving the necessary seal.
3Ease of operation
If conventional lubricants are used during pressing, then friction is reduced, but residual lubricant may contaminate the sample in life science applications
Solution Approach 1:
The volatile carrier fluid is designed to completely evaporate after pressing, leaving no residual contamination. Although the lubricant suspension serves a temporary function during assembly, its transient nature ensures no harmful residues remain to contaminate samples in sensitive life science applications.
Solution Approach 2:
The carrier fluid undergoes a phase transition from liquid to vapor after the pressing operation. This evaporation eliminates the lubricant's carrier medium, ensuring that only the inert metal particles remain in the seal, thereby preventing sample contamination while maintaining ease of operation during assembly.
4Reliability
If the window and probe body materials are selected for chemical resistance, then hermeticity and longevity are improved, but thermal stress between dissimilar materials increases
Solution Approach 1:
The metal particle-containing lubricant serves as an intermediary layer that accommodates thermal expansion differences between the window and probe body materials. This intermediate coating flexes and adjusts with temperature changes, reducing thermal stress while maintaining the hermetic seal provided by the metal-to-metal contact.
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 reduces pressing forces on the window while maintaining high retention forces, ensuring a hermetic and chemically resistant seal, and is suitable for applications like Raman spectroscopy, improving upon existing compression bonding techniques by enhancing seal integrity and reducing the risk of contamination.
Implementation Method 1
pressing the window into the aperture in the body such that the carrier fluid evaporates, leaving the polymer particles to fill interstitial surface voids
Implementation Method 2
applying a lubricant for friction control to at least the sidewall of the window or the sidewall of the aperture
Data Source
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AI summary
An improved method of sealing a window (302) into an aperture in a body (304) uses a lubricant comprising polymer particles (306, 308) suspended in a volatile, low viscosity, low surface tension carrier fluid. The carrier fluid is applied to one or both of the sidewalls of the window (302) and aperture, and the window (302) is pressed into the aperture such that the carrier fluid evaporates, leaving the polymer particles (306, 308) to fill interstitial surface voids, while enabling the sidewall of the window (302) to make intimate mechanical contact with the sidewall of the aperture. While having broader application, the present disclosure finds particular utility in optical characterization techniques based upon the Raman effect and fluorescence probes used in process monitoring and control.