Dispense on the fly

Hello everyone, im searching for someone with knowledge about the dispense on the fly step on a Microlab Star.

What i observed so far is:
I got it working for a single plate even with excluded wells, but if there is more positions in the sequence than volume in the tips, the Microlab processes the sequence without error. The result is that columns will only be partly filled or empty.

Does anyone have a smart idea how i can loop the dispense on the fly over more than one plate with a new aspirate in between?

Hi Michael,

To ensure even distribution of liquid to each target well from a parent channel during a dispense on the fly step, the key step parameter is X speed (the speed at which the channels will traverse labware during shot delivery).

The dispense rate during delivery is modulated by the liquid class, so the X speed should be configured such that X travel and plunger/dispense movement end at the same time (at the end of the plate). If the X speed is too slow, then the dispense will be complete before reaching the end of the plate. If the X speed is too fast, the channels will reach the end of the plate too early, and the channels will over deliver the remaining volume to the final set of wells.

An X speed of 0 (auto) will trigger VENUS to auto-calculate and apply an optimized X speed for the dispense and labware. Of course, this is ultimately a theoretical starting point and may need to be fine-tuned for different liquids and liquid classes.

Regarding using a loop to dispense to multiple plates, once your dispense parameters have been tweaked to consistent and robust performance (based on the above), I would program the same way as any other aspiration and dispense loop which use single steps. The specific logic and sequence handling used will vary per your scenario/requirements. In your case, each iteration of the loop would process a single plate.



1 Like

Hey Nick,
thank for your reply. Setting up the dispense to fit on one plate wasn’t that hard and is already workingexcept when you have more liquid to dispense than a tip can hold.
For example:
We use a 12 Channel Head (in this specific case with 1ml Tips) with Portrait plates. When dispensing 180µL to each well, the first 5 Wells will have the exact amount of 180µL. The 6th Well is left with only 100µL and the Wells 7 and 8 are empty, because the Head doesn’t stop, even though it should know that there is no more volume left and should give an error.
Do i need to fiddle around with sequence calculating and setting new endpoints in order to stop the head and get new liquid?

For the normal dispensing loop i usually break the dispensing loop on liquid error to get new volume, or calculate beforehand how many dispenses it can do.

What are your advices?

If it were me, I would run a calculation to determine if my total dispense volume per channel exceeds the maximum volume supported by the liquid class being used. In these cases, I would opt to perform multiple dispense on the fly commands for the same plate, in which each iteration would dispense to the entire plate at a reduced volume, where the multiple steps to the same plate would ultimately yield the target volume per well.

In your case, you are targeting 180uL per well at 8 wells per channel (1.44mL), using 1mL tips. The minimum number of iterations needed to achieve this using 1mL tips is 2. The simplest option in this case is to divide the target volume by the number of iterations, and repeat the step accordingly in a loop.

This would be easier than making a grouping of partial sequences that would comprise the plate, and takes the same amount of time.



Hey Nick,
that is as embarrassingly simple as it is clever. I will try it and reply the results. I will also do some time stopping to get a rough idea how this will affect my runs.

Thank you!