Help with sticky residue on MTPs and "Check if Plate exists" tap feature with CO-RE Grip

Good afternoon everyone,

I just joined the community today but I have been reading through all of the forums and can not thank everyone enough for all of the amazing help!

We have an issue on our STARs that I am hoping there is a solution for. Our methods use the CO-RE grippers to move our MTPs from location to location around the deck. To confirm successful movements we implement a plate tap with the CO-RE paddles. Some of the MTPs have been previously sealed with an adhesive film for either cold storage or PCR. The seal material used claims that no residue will be left behind when peeled, but in my experience this is not the case. There have been multiple instances of the CO-RE paddles sticking to residue left over from seal material which caused the MTP plate to flip over off the carrier. As far as I know, successful movement with the CO-RE paddles requires a “plate tap” to check for the plate presence.

To mitigate risk to the MTP, the “Plate Tap” has been removed on certain plates that may have seal residue on them, but in turn we have lost the ability to know if movements were successful. This leads to transfers to the MTPs destination position but the plate was never moved successfully from its source( ie tabbed carriers were gripping the MTP with enough force where the CO-RE paddles couldn’t pick it up).

Is there a way, with the CO-RE paddles, to confirm if a plate movement was successful without the tap feature? Any guidance on this issue is so greatly appreciated. Thank you so much everyone and have a wonderful weekend!

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Hi Mark, and welcome to the forum!

While there may be a couple options that can help here, I’d like to preface the post by stating that it sounds like your observed CO-RE grip ‘Get Plate’ and ‘Place Plate’ step performance is less robust than typical, and could be subject to some optimization in order to prevent transport issues entirely. Dropped plates should be extremely atypical.

For starters, I’d double check that your labware definitions are accurate and true to the plate, and also ensure that the taught deck coordinates for your plate positions are representative. You’ll also want to ensure that your grip parameters are optimal. I typically recommend using as accurate a grip width as possible relative to the grip height used, and apply 50% force. For typical MTP style plates, 3mm grip height is good and what I almost always use. Additionally, I like to slow down the Z speed during placement just a bit (relative to default 128.7mms) to around 80mm/s, and use a 1mm press down distance, which provides an additional downwards ‘shove-like’ movement at the end of placement into the locator.

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tabbed carriers were gripping the MTP with enough force where the CO-RE paddles couldn’t pick it up

This also strikes me as abnormal. Would you mind providing a bit more detail here regarding the style of carriers? This should not be an issue under normal circumstances.

While the ‘Check if plate exists’ feature is certainly useful, I would not qualify it as a requirement for robust CO-RE grip steps

That all said, there are other options to get the channels to interact with a plate after placement has occurred. You’ll see numerous mentions of the STAR Tools suite all over the VENUS section of the forum, which includes a Channel Tools library that features numerous useful custom channel functionality. In your case, there are two functions that may be of interest to you:

Note that neither of these will be particularly helpful if there isn’t a region of the plate that doesn’t have significant adhesive on it.

STAR Channel Tools::MOVE_CheckPlateWithTwoChannels

This is the most similar to the 'Check if plate exists, but allows for some customization. If there are regions of the plate less prone to adhesive residue after peeling, then you can customize the ‘tap width’ to whatever you want (relative to plate center). Additionally, you have the option to have the two channels that will perform the tap to pick up tips prior to the function. This will significantly decrease contact area relative to two CO-RE paddles.

STAR Channel Tools::PLATE_STACK_CountPlateStacks

This function will use a channel (no tip or CO-RE tool required to be loaded) to ‘probe’ a stack of labware and return a count of stacked labware present at the site(s). This works by sending a channel down gently in Z until it makes contact with labware dead-center. While this was intended primarily to confirm labware counts loaded in stacks, it also works with ‘stacks of one’ with unstacked labware. If no labware is present at the sequence site, then the function will yield a count of 0.

Hope this helps!

-Nick

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In my experience, the check if plate exists functionality fulfills two tasks:

  • check if plate exists (obviously)
  • pull down slightly elevated placed plates

That said, to overcome the mentioned issues with the grippers tapping the plate, you could also think about reserving one tip per run for that task. You could pick up the tip to sense at a desired coordinate (e.g. a corner which is not sticky) if there exists a physical object with the expected z-value and then place the tip back in the tip rack for re-use.

However, that was just a rude workaround and I second Nick’s recommendations to optimize the plate transports in first instance.

@NickHealy_Hamilton, may I comment that it might by risky in a long term to touch plates covered by known sticky residues directly with the pure channels? I would rather not recommend that.

Cheers
Max

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Another option would be a vision-based system to confirm the plate is in the correct deck position rather than touching it with the CO-RE grips - sounds like a good use case for LabEye or similar! (@Shaik would be the person to contact for LabEye)

Hi Mark,
If you like to learn how LabEye can solve this for you feel free to contact me via email shaik@robiotec.com and I can give you a quick demo.
LabEye can visually detect many aspects of the liquid handler deck and allow you to solve problems and achieve workflow robustness.
Shai

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Hi Max,

may I comment that it might by risky in a long term to touch plates covered by known sticky residues directly with the pure channels? I would rather not recommend that.

Absolutely - I would only have the stop disc make contact with fresh or otherwise unsoiled labware surfaces. I should have further elaborated in the post that the plate stack count function will also work with a tip loaded on the channel which will probe the stack/plate center. This is likely ideal in this particular case.

Thanks!

-Nick

Thank you so much for all of the amazing suggestions, I have some things i need to test out, I am so excited! In an ideal state implementing Labeye and switching to heat sealed plates will cover all the bases. I will be testing these suggestions today and share my findings! I can not thank everyone here enough for the help!

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