Syringe Needle Testing
Syringe needles must be tested to ensure patient safety. Most common tests include tension tests, applying an axial force to the needle and hub, and needle penetration tests to measure the force a needle requires to penetrate a surface. ISO 11070 Annex 1 or ISO 7864 are most commonly followed for testing the union strength between the needle hub and needle. For glass syringes where the needle is adhesively bonded to the syringe, ISO 11040-4 Annex G.1 is most commonly followed. For needle insertion force, the most common testing parameters are typically outlined by the needle manufacturer and characterized by needle geometry, sharpness, and end-use application. The reference standards used for needle penetration testing include ISO 7864 (DIN 13097-4) and ISO 11040-4 Annex F.1. For both test types, the responsiveness of the system and accuracy at low-force measurements are critical. Testing the union between the needle and needle hub can be challenging due to the cyclic nature of these tests, and the relatively fast testing speeds required. For instance, ISO 11070 Annex 1 specifies needles be tested at a rate of 100 mm/min in tension and compression to 10 N or 20 N, depending on the needle gauge. With such low forces and a relatively fast test speed, overshoot is possible.
For testing the needle and hub to ISO 11070, we recommend using a 5900 Series system and a high data rate to improve the responsiveness of the systems. Needle insertion force often requires low forces, under 10 N. Many injections are done into a patient's arm, making it difficult for a nurse or doctor to apply a force greater than 2 pounds to eject medication. In addition, many needle manufacturers want to quantify the frictional force required to pull a needle out of a patient's arm. Given that the frictional forces are typically in the 0.05 - 0.1 N range, we recommend using a small 10 - 50 N load cell for this application. In addition, the needle penetration medium chosen will affect results. We recommend using a medium that best mimics your end application for the needle. From experience, a thin sheet of ethylene propylene diene monomer (EPDM) rubber is a good medium to use for mimicking the skin.