Syringe Needle Testing

syringes with needles

There are multiple testing standards outlining methods for evaluating straight stainless steel needles used in healthcare applications. These standards are used by injection device manufacturers and the pharmaceutical companies that use them for drug delivery. Testing standards for syringe needles are necessary in order to regulate the products that reach the healthcare frontlines. They are critical for ensuring that sharps injuries are prevented and that injection doses can be delivered successfully. Failure can result in injury to the patient or the healthcare professional administering the drug. Failure can also cause an incorrect dosage to be administered to the patient, which leads to additional adverse effects. There are a number of testing standards that follow the raw material through the entire product development process:

ISO 9626

ISO 9626 is typically the first standard referenced, as it defines the mechanical properties requires for stainless steel tubing intended to be manufactured into needles. This standard includes methods to assess the strength and durability of the steel tubing to ensure it meets the requirements necessary for the end product. The required forces are dependent on the needle gauge and wall thickness, two factors that will dictate which application the needle will be used for. Testing is performed using a three-point bending assembly to determine the stiffness of the material. Additionally, a cantilever bend test is performed to assess the tubing's ability to withstand breakage. This test is critical to ensure the needle can withstand the shearing forces it may encounter in clinical environments.
Instron 68SC-1 with 3 point bend fixture

ISO 7864 

After the raw tubing has proven it meets the required specifications, it is further machined to have a beveled fine point and mated with a hub to ultimately attach to medical devices. ISO 7864 tests the finished component, evaluating the penetration force of the needle tip as well as the bonding strength between the needle and the hub. The substrate choice for penetration is critical in gathering valid data from the test, and ensuring the substrate layer is taught prior to testing is also very important for getting repeatable results. The standard explicitly outlines the options available for testing.

ASTM F3014

Curved needles are used primarily in surgical applications for wound closure. Due to their unique geometry, they introduce additional testing challenges. ASTM F3014 outlines the needle penetration force evaluation specific to curved needles, and Instron offers a specialized curved needle system capable of applying rotary motion instead of linear force to accommodate this application.

ISO 11040

ISO 11040 outlines the tests required for needles that are staked into the end of a glass syringe. These involve the pull-out force of the needle as well as the penetration force. For needles used in conjunction with cartridge-based pen injectors, as is typical with insulin pens, the interaction between the needle component and the pen must also be tested. This evaluation mainly focuses on the functionality of the device, quantifying the torques required to assemble and disassemble the needle hub from injection device. As with the other standards discussed, the bond strength between the needle and hub must also be determined.

Materials Testing System

Syringe needle testing should be performed on a low force universal testing system such as Instron's 68SC-1 with Bluehill Universal software. Penetration forces are less than 10 N but for all other tests 100 N capacity is appropriate. ISO 11608-2 testing requires Torsion Add-On 3.0.  For ISO 9626, custom test fixtures are required (bend fixture and cantilever bend fixture). When testing the needle hub bond strength, proper alignment is required between the hub and the needle. Any angular or concentric misalignment can cause additional force to be required for the needle removal.




ISO 11040 Test Setup
1) 6800 Series Universal Testing System
2) Bluehill Universal Software
3) 2527 Series Load Cell
4) Torsion Add-On 3.0
5) CP132121 Modular Test Fixture

 

ISO 11040 test setup

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