ISO 7864
Needle Penetration and Drag Force Test
ISO 7864 is a crucial standard for testing the needle penetration and drag forces that needles must endure when inserted into various substrates. This test is essential for ensuring the reliability, safety, and performance of needles used in medical devices.
What Is ISO 7864?
ISO 7864 defines the test methods for measuring the penetration force and drag force exerted by needles as they are inserted into different substrates. The standard is commonly used to evaluate the performance of hypodermic needles, ensuring that they meet the necessary quality and safety requirements for use in medical applications. It specifically addresses two key forces: the needle penetration force (the initial force required to penetrate a material) and the drag force (the frictional force experienced as the needle moves through the substrate).
The Importance of ISO 7864 Testing
Needle Penetration Force Test
The needle penetration force test measures the peak force needed for a needle to penetrate a specific material. This test is essential for ensuring that the needle can easily penetrate the skin or other target materials without causing unnecessary pain or damage.
The procedure typically involves inserting the needle into a substrate at a specified speed, usually 100 mm/min, while a force gauge measures the penetration force. The test results provide valuable data on the strength of the needle, which can influence the choice of materials used for the needle and its design.
Needle Drag Force Test
Once the needle has penetrated the substrate, the needle drag force test measures the friction force that resists the needle’s movement. The drag force is important for evaluating how smoothly the needle moves through tissues or materials, which is critical for medical procedures such as injections or biopsies.
The drag force is calculated by analyzing the force profile generated during insertion. The test results help manufacturers fine-tune the needle’s design, ensuring that the needle moves smoothly without excessive resistance or friction, which could affect the overall performance and user comfort.
Apparatus and Equipment for ISO 7864 Testing
Force Measurement Apparatus
ISO 7864 requires the use of a force measurement apparatus equipped with a load cell that accurately measures the forces during both the needle penetration and drag force tests. The apparatus must be able to hold the needle securely and move it at a specified speed to simulate real-world conditions accurately.
Substrate for Testing
The substrate used in ISO 7864 testing plays a critical role in ensuring accurate and reproducible results. Common substrates include natural latex rubber, polyurethane, silicone rubber, and polyethylene, each selected based on its hardness, thickness, and other properties. These materials mimic the type of resistance that needles would face during real medical procedures.
Needle Holder and Testing Conditions
A needle holder is used to securely fix the needle during the test. The test must be performed under standard laboratory conditions, with temperature and humidity controlled, to ensure consistency across tests. The needle is moved into the substrate at a constant speed until the desired penetration depth is reached.
ISO 8871-5 Testing Procedures - Perform Penetrability Testing (ISO 8871-5 Annex A)
After Testing:
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Data Collection and Calculation
Data is collected during the test, and the mean drag force and peak penetration force are calculated. These values provide key insights into the performance of the needle during insertion. -
Analyzing Results
The test results are analyzed to determine the average values and standard deviations of both the drag force and penetration force. These metrics help assess the needle’s overall performance.
The testing process outlined in ISO 7864 is designed to evaluate both the needle penetration force and needle drag force through a structured series of steps.
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Mounting the Needle and Preparing the Substrate
The needle is securely mounted on a force measurement apparatus equipped with a load cell that will record the forces during the test. The substrate is placed securely in the substrate holder, ensuring that it is aligned properly for the test. The substrate should be held firmly in place, with a target penetration area clearly visible. -
Moving the Needle
The needle is moved towards the substrate at a specified speed, typically 100 mm/min. The needle begins to penetrate the material, and the force applied is recorded. -
Measuring the Penetration Force and Drag Force
The initial penetration force is measured as the peak force required to break through the material. This force corresponds to the maximum force at the moment of initial penetration. After the needle has penetrated the material, it continues to move forward. The drag force, or the frictional resistance the needle faces as it moves through the substrate, is recorded. -
Retracting the Needle
Once the needle has been inserted to the prescribed depth, it is retracted from the substrate.
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