Plastic side-wall tabs on microtiter plates

Hi All,

I am curious about labware shapes, particularly about what we call “tabs” on microtiter plates. These tabs are small raised sections of a skirt on the long side of microtiter plates. I assume that someone decided that these were a good idea for some reason but for the life of me I cannot think of a positive effect these lend to the plate. In our hands, these “tabs” are creating nothing but chaos as the gripper teachings on our STAR must be absolutely dead on center +/1 1mm otherwise the plate flips around in the gripper.

So, automation experts, I ask: what are these for? Why do they exist? What are their purpose? Any tips on using labware with them when the tolerances with the gripping devices are so small? If someone has been in the lab automation game for a long long time and knows why these are a good thing, I’d LOVE to hear about it!


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this is the first time I am seeing these tabs. why not use a different manufacturer without the tabs? or you can grip it using the larger opening.

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We are finding that more manufacturers than you’d think have these tabs on the plate. We are also a bit constrained by needing special coatings on the plates which limits our options. The plates are lidded when we are gripping and moving them so we have to grip lower to the skirt and our orientation won’t allow for landscape gripping.

It’s a good question :rofl:

I have seen them myself but also haven’t figured out any use for them.

Regarding your problem, if your plate is not too heavy you can try gripping off center. You can use the VirtualLabware library to make the gripping command think the center is shifted.

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Hmm interesting. I wonder if the tabs maybe aid stacking somehow?

Thanks! Yes we have considered that but it may be worth a very serious consideration in the future if we do not find a manufacturer without the tabs.

simple solution. offset the grip. don’t grip it in the middle. considering it’s not a deepwell with full liquid, the iSwap is more than capable of gripping it from one side. I’ve done it before :slight_smile:

I’d be really curious if anyone knew the reason/purpose behind these tabs. They seem to be present on all the plate vendors I am familiar with, but I agree, they seem like they could cause issues.

I’ve always called them pinch bars and I find them quite useful when moving plates with lids. For plates with very skinny skirts (like the one in the photo) your robot cannot reliably pick it up by the skirt. So that leaves the area between the skirt and the lid for picking up a plate. If your lid is quite deep you may only have a few millimeters left for the robot to pick up the plate. Some robot fingers will actually be larger than the area you have left. In comes the pinch bar, this supplies an area for the robot finger to grip the plate when it has a lid and while still allowing a small skirt height.

What’s the purpose of a small skirt height? I don’t know, but most plates have a very small skirt. Costar plates are some of the few plates that I can think of that typically have a very tall skirt.