Pipette Tip Sealing Against Piston to Eliminate Shaft Seal
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Solution Overview
Problem
Traditional air displacement pipettes face issues with seal failures between the piston and the shaft, leading to leaks, inaccuracy, and increased maintenance needs, as well as inefficiencies due to ullage space and cross-contamination protection methods.
Innovation Solution
A pipette design with a piston that seals directly against the disposable tip, eliminating the need for a seal between the piston and the shaft, and using a two-piece tip configuration with a membrane filter for improved sealing and reduced maintenance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a seal is placed between the piston and the shaft, then air-tight sealing is achieved, but the seal breaks down and leaks over time requiring maintenance
Solution Approach 1:
The seal is extracted from the pipette body and transferred to the disposable tip. The piston no longer seals against the shaft, eliminating the sealed chamber. Instead, the tip seals against the piston, and the tip itself provides the sealed environment. This resolves the contradiction by removing the long-lived seal from the system while maintaining sealing functionality through the disposable tip.
Solution Approach 2:
The sealing function is transferred to the disposable tip, which is replaced frequently. The seal is now part of the cheap, short-lived tip rather than the expensive, long-lived pipette body. This resolves the contradiction by accepting that the seal has short service life (matching the tip replacement cycle) rather than requiring long-term durability.
2Reliability
If a seal is placed between the tip and the shaft, then air-tight sealing is achieved, but friction increases making tip replacement difficult
Solution Approach 1:
The seal between the tip and shaft is removed entirely. The tip no longer seals against the shaft; instead, it seals against the piston. This eliminates the source of high friction at the tip-shaft interface, allowing easy tip replacement while maintaining sealing through the tip-piston interface.
3Measurement precision
If the piston seals against the shaft, then accurate liquid measurement is achieved, but maintenance requirements increase due to seal failure
Solution Approach 1:
The sealing function is transferred to the disposable tip, which includes an integrated seal that contacts the piston. When the tip wears or becomes contaminated, it is discarded and replaced, eliminating the need to service the pipette's internal sealing mechanisms. This resolves the contradiction by making the seal replaceable as a complete unit rather than requiring disassembly and repair of the pipette body.
4Stability of the object's composition
If ullage space is maintained in the shaft, then piston movement is cushioned, but measurement accuracy decreases
Solution Approach 1:
The large ullage space in the shaft is eliminated by transferring the sealed chamber to the tip. The piston moves within the tip rather than the shaft, creating a compact sealed environment with minimal air volume. This resolves the contradiction by removing the source of measurement error (large air cushion) while maintaining piston stability through the confined space in the tip.
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 design reduces maintenance requirements, enhances accuracy by minimizing ullage space, and allows for efficient low-pore size membrane filters, improving pipetting precision and reducing user technique-dependent errors.
Implementation Method 1
efficient low-pore size membrane filters
Implementation Method 2
a seal between the piston and the tip, and no seal between any portion of the tip and the shaft
Data Source
Figure 1
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AI summary
A sealing pipette tip includes features to seal the tip directly against the piston in an air displacement pipette, avoiding the need for a piston seal within the pipette. This configuration reduces potential points of failure, allows the pipette-tip interface to be optimized, and improves liquid handling characteristics of the pipette.