Hello automation engineers!
We’re trying to perfect a workflow on an opentrons system that requires incredible precision for pipetting into a 384 wellplate. Our issue is as you likely guessed, p20 tips for opentrons have a decent margin of error when it comes to how straight they are. Does anyone know of any ultra straight pipette tips we could try out? I’m open to all ideas at this point
Thanks for your input!
Pipette tips are probably only part of the problem. With any sort of physical pipette mounting system (as opposed to a mechanism like Hamilton’s CO-RE system) there will definitely be some amount of variation. That being said, 384 shouldn’t be too incredibly difficult to hit, even with something like 1000µL tips. You might want to try finding a reference on the worktable and make sure your pipettor is aligned perfectly along each axis and that there isn’t any roll/yaw/pitch type deviation. After that, identify if there are issues along the actual pipettor mounting tips, like if there’s a “sawtooth” pattern you can identify at the end of the mounted tips. One other tip is that if you are picking up tips too many times, this can lead to loss of seal between tip/mounting cone and general deformation of the tip mounting cup.
If those are both perfect… then yeah, you might want to spend a bit more on tips.
Ive actually found that picking up tips with a miscalibrated opentron over time permanently deformed the part of the channel that contacts the tips.
Interesting insights! We can certainly hit a 384 well plate, however we want to pipette pretty precisely in the center of the well. So getting into the well isn’t the problem, but getting in the center is the hard part, hence I’m looking for straighter tips we can use.
Hello,
I cannot comment on the positioning accuracy of an Opentron as I’ve had too limited experience with it but you will need to look at device + tip combination to reduce the variation to a minimum.
Two things you could try to reduce it on your platform:
raise the target 384-well plate as high as you can, with the goal of minimizing the Z-travel of your pipetting channel. Depending on how these are designed, this can have a big effect. 3D print this plate holder if there are none available commercially.
if you have the chance to create your own labware and you are settled on which disposable tip size you’re going to use: design a “tip guide plate” to sit above your 384-well plate. Picture the holes in this plate to be conically shaped and basically pushing your disposable to a specific location as it travels through this guide plate. Be aware though that the side force on the tip doesn’t cause a detach.
Hi,
I would also look at the precision on the plate locator. I have not used the Opentrons, but Hamilton and other liquid handler manufactures make high precision locators for plates to help with reproducibility in placement.
I also find that even the bigger companies, they can be pretty tough at uniformity of their spacing on a plate.
if you’re using a 384 plate and trying to hit every single well dead center with an 8 channel or 96 head… you’re setting yourself up for some problems in the future. Even the best and most precise liquid handlers have tolerances for their X,Y,Z calibrations which lead to gradual variations.
My experience is that also the rack holder of the carrier has an impact, meaning that X,Y coordinates of the plate may also vary.
Thinking outsode the box (I have no idea if applicable on your robot): maybe using one of the channels to accurately measure relative coordinates of the pipetting channels to the cavities during the pipetting step could help?