Autoinjector Shape Memory Alloy Needle Insertion Mechanism
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Solution Overview
Problem
Existing autoinjectors require substantial user effort for needle insertion, are not easily adaptable to different syringe types or drugs, and lack effective safety mechanisms to prevent needle access after injection.
Innovation Solution
A device with a rotatable cylinder part and radial projection mechanism that reduces the force required for needle insertion, allows for easy adaptation of motor parts to different syringe sizes, and incorporates a spring-based system for both needle insertion and injection, along with a needle protection mechanism that activates automatically upon withdrawal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If existing autoinjectors use traditional triggering mechanisms, then needle insertion can be automated, but substantial user effort and high activation force are required
Solution Approach 1:
The patent replaces the traditional mechanical spring-based triggering system with a shape memory alloy (SMA) actuator that uses thermal-mechanical coupling. The SMA element undergoes phase transformation when heated, generating sufficient force for needle insertion without requiring high user activation force. This substitutes a purely mechanical system with a smart material-based system that converts thermal energy to mechanical work.
Solution Approach 2:
The patent changes the physical state of the shape memory alloy from austenite to martensite phase through temperature control. By heating the SMA element above its transformation temperature, it recovers its pre-programmed shape and generates insertion force. This parameter change (temperature-induced phase transformation) enables automated needle insertion with minimal user effort.
2Manufacturing precision
If motor parts are designed for specific syringe types, then injection precision is maintained, but adaptability to different syringe sizes and drugs is reduced
Solution Approach 1:
The patent designs the motor part with a universal interface that can accommodate different syringe types and sizes. The triggering mechanism and SMA actuator are configured to work with various container geometries, allowing a single motor part design to serve multiple injection purposes. This universal design maintains injection precision through controlled thermal-mechanical actuation while enabling adaptability to different syringes and drugs.
3Reliability
If needle protection mechanisms are added to prevent needle access after injection, then user safety is improved, but device complexity increases
Solution Approach 1:
The patent integrates the needle protection function into the existing container and SMA actuator structure. The container is designed to automatically cover the needle after injection, and the SMA actuator serves dual purposes: driving needle insertion and triggering the protection mechanism. This merging of functions achieves needle protection without significantly increasing device complexity.
Solution Approach 2:
The needle protection mechanism operates automatically through the same thermal-mechanical actuation that drives needle insertion. After the injection is complete, the SMA actuator's phase transformation naturally triggers the container to move into the protection position, covering the needle. This self-service mechanism eliminates the need for separate manual protection actions or additional complex control systems.
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 device enables effortless needle insertion with minimal user effort, allows for easy adaptation to various syringe sizes and drugs, and ensures safe operation by preventing needle access after injection, providing a smooth and secure injection process.
Implementation Method 1
The actuator comprises a shape memory alloy element which is capable of transforming reversibly between an austenite phase and a martensite phase
Implementation Method 2
the transformation from the martensite phase to the austenite phase being achieved by heating the shape memory alloy element above an austenite finish temperature
Implementation Method 3
biasing means, in other words a biasing element, for example a spring, for biasing the container in the proximal direction
Data Source
AI summary
The present invention relates to an automatic injection device (1) comprising: a container (2) having a longitudinal axis A and movable between a first position and a second position, in which the needle is inserted, biasing means (8), for moving the container to its second position, retaining means (70, 74, 74b) for maintaining said biasing means in a first stressed state, triggering means (90, 91e) for releasing said retaining means, said retaining means comprising a lever member having a rotatable cylinder part and a radial projection extending therefrom, said radial projection being in a first angular position when said retaining means is in its passive condition, said radial projection being in a second angular position, different from said first angular position, when said retaining means is in its active condition, said rotatable cylinder part being included in a transversal plane of said longitudinal axis A.