Drug Delivery Impact Testing to Prevent Syringe Damage
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Solution Overview
Problem
Automated drug delivery devices face challenges in predicting and preventing damage to syringes and drugs due to excessive loads applied by drive mechanisms, particularly in delivering high viscosity biologics, which can result in syringe fractures and patient discomfort.
Innovation Solution
An impact testing apparatus and method that simulates the operation of drug delivery devices, measuring characteristics such as forces, pressures, and velocities during impact events using a guide sleeve, impactor, energy source, and monitoring system to identify potential failure points and optimize device design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the drive mechanism applies sufficient force to deliver high viscosity biologics, then the drug delivery capability is improved, but the syringe and drug may be damaged due to excessive load
Solution Approach 1:
The patent applies beforehand cushioning by designing a drive mechanism with a compliant interface or cushioning element between the plunger rod and plunger. This cushioning element absorbs excessive forces before they reach the syringe, preventing syringe fracture while still delivering the required force to propel high viscosity biologics. The cushioning acts as a protective buffer that limits peak impact forces.
Solution Approach 2:
The patent employs parameter changes by modifying the force-displacement characteristics of the drive mechanism. Instead of a linear spring, the system uses a progressive spring or variable stiffness mechanism that adjusts the force applied to the plunger throughout the stroke. This allows sufficient force delivery for high viscosity drugs while limiting excessive peak forces that could damage the syringe.
2Productivity
If the drive mechanism operates at higher velocity to deliver drug faster, then the productivity is improved, but the kinetic energy applied to the syringe increases causing potential damage
Solution Approach 1:
The cushioning element is positioned to engage before the plunger rod fully impacts the plunger, absorbing the shock of high-velocity operation. This allows the drive mechanism to operate at higher velocities for improved productivity while the cushioning prevents excessive impact forces from damaging the syringe or drug.
Solution Approach 2:
The patent applies dynamics by using a progressive spring with variable stiffness that adapts to the operating conditions. As the plunger advances and viscosity resistance increases, the spring progressively stiffens to maintain adequate delivery force. During high-velocity operation, the dynamic characteristics of the spring and cushioning elements absorb impact energy while still enabling fast drug delivery.
3Ease of operation
If a spring-type drive mechanism is used to provide continuous force, then the ease of operation is improved, but excessive force is applied at the beginning of the plunger stroke causing damage
Solution Approach 1:
The patent replaces the linear spring with a progressive spring or variable stiffness mechanism that changes its force characteristics during operation. The spring is designed to be softer at the beginning of the plunger stroke, reducing initial impact force, and progressively stiffer as the plunger advances, ensuring adequate force delivery for high viscosity biologics throughout the stroke.
Solution Approach 2:
A cushioning element is introduced between the plunger rod and plunger to absorb excessive initial forces. This cushioning layer allows the spring-type drive mechanism to operate automatically while limiting peak forces at the start of the stroke that would otherwise damage the syringe or drug.
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 to design drug delivery devices that minimize component failure and drug damage, ensuring reliable and comfortable operation.
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 load cell configured to output a force signal representative of one or more impacts caused by the impactor
Implementation Method 3
a pressure sensor configured to output a pressure signal representative of a pressure of a fluid expelled from the outlet of the syringe
Data Source
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 impactor 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 impactor and the plunger so that the impactor 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.