Hi everyone,
Today we ran into something strange while playing around with the LVK during a Liquid Class investigation.
During the dispense — as you can see in the video— the air transport gets aspirated into the liquid without moving up (here we exaggerated the air transport for the video). Yet in our dispense step, we requested 30 mm using the Retract Distance for Air Transport.
Please find the steps attached. I’m really confused: this parameter works well for the aspirate but not for the dispense. Same behavior observed on both the MPH96 and the 8 channels. Could it be linked to the jet empty?
If anyone has any ideas, I’d appreciate the input.
By the way, our systems are Vantage 2.0 running on Venus 4.6 and VoV 2.2.13.4 Rev T.
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Hi @Clinical_Dev ,
I can see from your liquid class that you are using a Jet Empty dispense mode. You can see within the liquid class settings that settling time and swap speed are grayed out for this mode. This is because for Jet Empty, the target is expected to be either empty or at least no touching of the liquid (dispensed above liquid level). I believe for this dispense mode that retract distance is not applied which matches what you are observing.
If you were to change to a surface empty dispense, then the expected behavior you described should be seen with the retract distance as this dispense mode is expected to touch the liquid on dispense and a retract distance is required to aspirate an air gap.
For Jet Empty, I would recommend updating the dispense height such that it does not come in contact with the liquid at any point in the dispense. If touching the liquid is required, then using a Surface Empty dispense mode is the path you should take.
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Hi @BrandonBare_Hamilton , Thank you for your answer
That’s exactly what I suspected as well. In my application we dispense into an empty plate, but it’s a foamy buffer, so we didn’t apply blowout but we observe a residual droplet. So we arranged the Jet Empty to end its stroke at the liquid surface.
Normally, with the black tips we wouldn’t have noticed anything, but here, as part of an investigation into tip reuse, we ended up using the transparent tips and spotted this phenomenon. I’m just a bit surprised the Help doesn’t mention that this parameter isn’t applicable in Jet Empty mode.
Then surface mode is what you need to use. 
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