Composite Syringe Plunger Stopper for High Dose Accuracy
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Solution Overview
Problem
Existing drug delivery systems, such as syringes and auto-injectors, face challenges in achieving high dose accuracy due to stopper distortion, air bubble variation, and hysteresis, which can lead to inconsistent medication delivery and increased complexity and cost.
Innovation Solution
A stopper design featuring a combination of elastomeric and rigid materials, where a semi-rigid or rigid insert is embedded within an elastomeric material, providing improved rigidity and reducing distortion and hysteresis, while maintaining a seal with lower contact pressure, and potentially coated with barrier films to prevent drug component leaching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional elastomeric stopper is used, then the device complexity is low and manufacturing is simple, but the stopper exhibits distortion and hysteresis that reduce dose accuracy
Solution Approach 1:
The stopper is constructed as a composite structure with a rigid central core (metal or rigid plastic) embedded within an elastomeric material. The rigid core provides dimensional stability and reduces distortion, while the elastomeric outer layer maintains sealing capability. This composite approach resolves the contradiction by achieving high dose accuracy through reduced hysteresis and distortion without requiring overly complex device architecture.
Solution Approach 2:
The stopper is divided into distinct functional zones: a rigid central core for structural stability and an elastomeric outer layer for sealing. This segmentation allows each portion to perform its specific function optimally, with the rigid core minimizing distortion and the elastomeric material providing compliant sealing, thereby improving dose accuracy without excessive complexity.
2Measurement precision
If a rigid material is used for the stopper, then distortion and hysteresis are reduced, but the contact pressure with the syringe barrel wall increases
Solution Approach 1:
The composite stopper structure with rigid core and elastomeric outer layer resolves this contradiction by having the rigid core provide dimensional stability (reducing distortion and hysteresis) while the elastomeric outer layer conforms to the syringe barrel wall, distributing and reducing contact pressure. This allows accurate dosing without excessive wall pressure.
3Reliability
If the stopper is made from a single material, then manufacturing is simple and cost is low, but it cannot simultaneously achieve low distortion and low contact pressure
Solution Approach 1:
The stopper uses a composite of rigid and elastomeric materials to simultaneously achieve low distortion (from the rigid core) and reliable sealing with reduced contact pressure (from the elastomeric outer layer). While the multi-material construction increases manufacturing complexity compared to single-material stoppers, it enables performance that single materials cannot achieve alone.
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
The stopper design enhances dose accuracy by minimizing distortion and hysteresis, maintaining a reliable seal with lower contact pressure, and preventing drug contamination, thus improving the reliability and safety of medication delivery systems.
Implementation Method 1
a second portion formed from a second material, wherein the second material has a greater rigidity than the first material
Implementation Method 2
The first material can comprise an elastomeric material, such as those materials typically used for stoppers
Data Source
AI summary
A plunger stopper configured for attachment with a plunger rod for use with a within a syringe barrel for high dose accuracy drug delivery. The stopper having a first portion formed from a first material and a second portion formed from a second material, wherein the second material has a greater rigidity than the first material and wherein the second portion is configured to be attached to a plunger rod. The second material can be in the form of an insert which functions to reduce the amount of distortion of the stopper during use, reduce air bubble size variation from fill to fill, maintain a seal with the inner wall of the syringe barrel with lower contact pressure in a resting state and reduce the amount of hysteresis of the stopper. The stopper can be adapted for use with infusers, pens, and other types of auto-injectors.