Convertible Plunger Design for Low-Force Syringe Dispensing
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Solution Overview
Problem
Existing plungers in drug delivery devices, such as prefilled syringes, face challenges in balancing container closure integrity and gas-tightness with the need for low and consistent plunger force during dispensing, while avoiding the use of flowable lubricants that can interact with the drug product and cause degradation or patient discomfort.
Innovation Solution
A convertible plunger design with a compressible and resilient storage sealing section that transitions from an expanded state to a constricted state, allowing for a gas-tight seal during storage and reducing the force required for dispensing without the need for flowable lubricants, achieved through a cylindrical exterior surface and a rigid internal portion that applies outward radial pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a rubber plunger is used to provide container closure integrity and gas-tight seal, then sealing performance is improved, but plunger force required for dispensing increases
Solution Approach 1:
The plunger is divided into two distinct sections: a rubber sealing section for maintaining container closure integrity and a smooth dispensing section for low-friction movement. This segmentation allows each section to perform its specific function optimally without compromising the other.
Solution Approach 2:
Different portions of the plunger are given different surface properties: the sealing section has high friction and compliance for gas-tight sealing, while the dispensing section has low friction for smooth movement. This local differentiation resolves the contradiction between sealing performance and ease of dispensing.
2Reliability
If the plunger is made larger in diameter than the internal diameter of the barrel to ensure gas-tight seal, then sealing performance is improved, but force required to advance the plunger increases
Solution Approach 1:
The plunger is segmented into a sealing section with larger diameter for gas-tight seal and a dispensing section with smaller, smooth surface for low-friction movement. This allows the plunger to maintain sealing integrity while reducing the force needed for advancement.
Solution Approach 2:
The plunger surface is differentiated locally: the sealing portion has high friction coefficients for gas-tightness, while the dispensing portion has low friction coefficients for easy advancement. This local quality variation resolves the force contradiction.
3Ease of operation
If flowable lubricants are used to reduce plunger force, then ease of dispensing is improved, but harmful interactions with drug product occur
Solution Approach 1:
The harmful flowable lubricant is completely removed from the system. Instead, a smooth dispensing section with low-friction surface properties is used, eliminating the source of lubricant-generated particles while maintaining ease of dispensing.
Solution Approach 2:
The plunger's smooth dispensing section acts as a disposable, single-use component that provides low friction without requiring persistent lubrication. This eliminates the need for flowable lubricants that would otherwise contaminate the drug product.
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 solution enables a break loose force and glide force below 15 N, ensuring comfortable administration and maintaining container closure integrity and gas-tightness, while preventing drug product interaction with lubricant-generated particles, thus optimizing plunger force and reducing manufacturing complexity.
Implementation Method 1
a compressible and resilient storage sealing section that is maintained in an expanded state by outward radial pressure provided by the internal portion
Implementation Method 2
The expanded state is reducible to a constricted state by an operation that is applied to the internal portion of the plunger to reduce or eliminate the outward radial pressure
Implementation Method 3
a liquid sealing section configured to provide a liquid-tight seal when disposed in a medical barrel
Data Source
AI summary
Disclosed are plunger assemblies including various convertible plungers and methods of making the same. Each plunger assembly is configured for disposition within a barrel of a medical container, e.g., a syringe, and displaced within the barrel from an engagement position to a release position. The engagement position is configured to provide a compression seal between a storage sealing section of the plunger and an inner wall of the syringe barrel. In the release position, the compression seal is reduced or eliminated. Also disclosed are methods for making convertible plungers and assembling them into syringes, e.g., pre-filled syringes.