Syringe Impact Testing for Autoinjector Load and Drug Damage
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Solution Overview
Problem
Automated drug delivery devices, such as autoinjectors, often apply excessive loads to syringes, leading to potential damage and discomfort to patients due to unpredictable kinetic energy distribution, especially with high viscosity drugs, making it difficult to predict syringe or drug integrity.
Innovation Solution
A testing apparatus simulating the operation of drug delivery devices, comprising a guide sleeve, impactor, energy source, and monitoring system, to measure and evaluate impact characteristics, including force, pressure, and velocity, facilitating the design of devices that minimize component failure and drug damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the drive mechanism applies sufficient energy for drug delivery at the end of plunger stroke, then the drug delivery function is improved, but excessive load is applied to the syringe and drug causing potential damage
Solution Approach 1:
The patent applies a progressive force mechanism where the drive mechanism increases its force output as the plunger stroke progresses. The force profile transitions from lower initial force to higher final force, matching the increasing resistance encountered during drug delivery. This dynamic force application ensures sufficient energy delivery at the end of stroke while avoiding excessive load at the beginning, thereby preventing syringe and drug damage.
Solution Approach 2:
The patent modifies the force parameter throughout the plunger stroke rather than maintaining constant force. By changing the force parameter dynamically - starting with lower force and progressively increasing it - the system optimizes energy delivery while minimizing harmful effects. This parameter change approach allows the drive mechanism to adapt its output to the actual resistance encountered at each stage of plunger advancement.
2Productivity
If the drive mechanism operates at higher velocity to deliver drug faster, then productivity is improved, but kinetic energy increases significantly causing potential damage to syringe or drug
Solution Approach 1:
The patent employs a staged or periodic force application pattern during plunger advancement. Rather than applying continuous high velocity and force, the drive mechanism progresses through distinct phases with controlled acceleration and force application. This periodic action allows the system to achieve productive drug delivery while managing kinetic energy levels to prevent damage to the syringe or drug product.
3Ease of manufacture
If spring-type drive mechanism is used to provide drive force, then ease of manufacture is improved, but excessive load is applied at the beginning of plunger stroke due to inverse relationship between spring length and applied force
Solution Approach 1:
The patent modifies the traditional spring mechanism to provide progressive force rather than the conventional inverse relationship between spring length and force. By redesigning the spring system or its engagement mechanism, the drive mechanism now applies lower force when the spring is compressed (beginning of stroke) and increases force as the spring extends (end of stroke). This dynamic force profile maintains ease of manufacture while eliminating the harmful excessive load problem.
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 apparatus provides empirical data for improving the design and manufacturing of drug delivery devices, reducing the likelihood of syringe fractures and drug damage by accurately simulating and measuring impact events.
Implementation Method 1
The energy source may be configured to reduce a distance between the impactor and the plunger such that the impactor strikes the plunger
Implementation Method 2
a pressure sensor configured to output a pressure signal representative of a pressure of a fluid expelled from the outlet of the syringe
Implementation Method 3
a first load cell configured to output a first force signal representative of one or more impacts caused by the impactor
Data Source
Figure 1A~1B
Figure 2A
Figure 2B
AI summary
Impact testing apparatuses are disclosed which simulate and measure various impact-related events associated with the operation of a drug delivery device. The impact testing apparatus may include an imapctor configured to simulate a plunger rod of the drug delivery device, and a guide sleeve configured to receive a syringe corresponding to the drug delivery device. The syringe may have a proximal end, a distal end defining an outlet, and an interior chamber extending between the proximal and distal ends and carrying a plunger. Additionally, the impact testing apparatus may include an energy source configured to reduce a distance between the imapctor and the plunger so that the imapctor strikes the plunger. Various sensors may be included to measure characteristics of one or more impacts caused by the impactor. Methods of impact testing a syringe filled with a fluid and carrying a plunger are also disclosed.