Bending the flex

[ajuavinett]

Hello fellow Neuropixels users --

Has anyone had any experience bending the probe flex cable at rather severe angles? Do we know for sure that this is going to result in probe failure?

We're developing a design for freely moving mice but the flex is a serious limitation. It twists almost immediately if suspended above the mouse's head. However, there isn't a clear way to mount it close to the mouse's head without bending it and while keeping the microax cable coming out of the top. If I wind the flex like a tight "S," I can get it in the configuration I want -- but that means two rather tight angles.

Thanks in advance for the input! Ashley

[apfdomanski]

Hi Ashley, My chronic rat implant design has the probe flex permanently held in a tight S-bend, attached to the headstage which is in turn attached to the inside of a plastic support piece. The flex is almost as tight as I can get it without permanent kinking . Other than the compact implant and clearance to reach optic fibre stubs, the main advantage is that I can plug in with minimal stress to all involved by connecting just the nano Omnetics connector. I've had no mechanical issues with this configuration and haven't seen any signal degradation or dropped packets. Hope that helps. Cheers, Aleks

[ajuavinett]

@apfdomanski thank you so much for sharing, that is incredibly useful and encouraging! Do you happen to have a photo of your implant that you'd be able to share?

[apfdomanski]

Sure - have sent you an email.

[nsteinme]

Here are some comments from Marius Bauza: "I never had a crease in my flex but i would advise against it. The minimum flex bending radius is probably around 5mm or so, so two little 3d printed spacers would achieve the required result."

and James Jun: "I agree with Marius. To reduce the extra length I bent the flex cable in “U shape” inside of the falcon tube with a bending radius of ~5 mm. [There is a photo] in our upcoming paper. I can also send some extra pictures I took."

Also, you could print the piece that I have uploaded here on the wiki from our mouse chronic implants and stick a dummy/broken probe in it - you will see that it also results in an S shape with pretty tight bending radius (maybe even <5mm), which was how I kept it for months on the mouse's head.

[ajuavinett]

Thanks @nsteinme & @apfdomanski -- I just folded the flex into an S (with as little crease as possible, using a spacer), and it seems fine! Hoping it holds up. Will update if anything changes.

update I've been folding the flex into a pretty tight S without any problems, at least in the short term.