I have a project in which I have to use a up to 2.5mm diameter needle with a 90 degree (L shape) angle similar than the one in the following picture: enter image description here

I say similar because there is only the tip of the needle is only 1mm since the 90 degree angle

I need to find some kind of material I can get a wire of that goes inside the needle that will bend so it moves back and forward throughout the L shape of the needle and strong enough so it can push a springed metal present at the 2 or 3 mm from the tip of the needle.

I have the dilemma that if the material is too stiff it won't easily go back and forward because of the L shape but if it is not enough it won't have enough strength to make the spring to compress on the tip end.

I thought about a wooden snake alike solution but since the wire must be so thin I can't find anything to make it of.

enter image description here

Maybe you have a better idea.

Thank you so much in advance

  • $\begingroup$ What is the inside diameter of the cannula? $\endgroup$
    – Eric S
    Commented Apr 2, 2020 at 14:38

1 Answer 1


Here is an idea: try using a bundle of very thin wires and fuse the ends together at the tip. You could prototype this with small gauge, multi-strand, electrical wire. Solder the ends together so you have a solid tip for pressing. You can buy stainless steel wire down to 50 microns very inexpensively and fuse the ends together if corrosion is a concern.

You will get the combined axial stiffness of the bundle because the fused tip along with the constraint of the needle tip will keep the wires bundled together while it pushes. The wires will be able to turn the corner more easily because they are able to move relative to one another in bending. It's important that you do not fuse both ends or you will loose some of this advantage.

You could try something like this: https://www.mcmaster.com/34235t27 (nylon coated) or this: https://www.mcmaster.com/3461t63 (uncoated)

They are braided bundles of 133 wires with an OD of 0.94 mm. I would suggest the uncoated version for most flexibility.


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