ePACE Pump Mapping

Experiments
1

Hi all,

Thanks for the excellent documentation and the amazing device We’re setting up ePACE on a newly acquired eVOLVER unit. Our configuration: 16 low-flow (~1 mL/min) and 32 high-flow (~45 mL/min) pumps. We plan to run 8 lagoons, using 8 vials as lagoons and 8 as reservoirs.

From the Experiment Setup page ( Experiment Setup | eVOLVER ), it looks like you run two low-flow lines per lagoon for inducers (e.g., arabinose + drift), which would consume all 16 of our low-flow channels. That would leave everything else (media→reservoir, reservoir→lagoon, and efflux) on the two high-flow arrays. I am a little unsure if we can run the vial to vial connections (resrvoir→lagoon) on the high-flow pumps, given the low turnover of the lagoons for some selection circuits. To make sure I understand your setup correctly, I came up with some questions:

Pump mapping assumptions

In your template and schematic setup (shown here, Experiment Setup | eVOLVER ) do you assume pumps 0–31 = high-flow and 32–47 = low-flow? If not, what’s the recommended way to declare a custom map (from the epace-template/pump_cal.json file I unfortunately could not get the settings, as flow rates are 0.75ml/s for all 48)?

Can high-flow pumps handle low hourly rates?
We’d like lagoon dilution rates ≤ 1 V/h (e.g., 5 mL/h into a 10 mL lagoon). A 45 mL/min pump dispenses ~0.5-0.75 mL per 1 s pulse, so to hit 5 mL/h we’d need ~1 s every 9 min (0.75 mL × 6.7 pulses/h ≈ 5 mL/h). Is that duty cycle reliable in practice, or do you strongly recommend reservoir→lagoon on low-flow only? Do you have a minimum reliable pulse width and/or max recommended bolus volume (as % of lagoon volume) for high-flow pumps to avoid oscillatory OD / mixing artifacts?

Additional documentation
If you’ve already built the dual-manifold setup for ePACE with two inducers per lagoon, could you share a picture or two of your tubing/pump routing and any epace-template code snippets and config files associated with it?

If the strong recommendation is to keep reservoir→lagoon on low-flow, we’ll either (a) add a small external low-flow manifold for inducers and free the built-in low-flows for reservoir feed, (b) reduce to a single inducer per lagoon, or (c) purchase another low-flow pump rack from you.

Many thanks and best regards!
—Jay

2

@Nate_Borders would probably be helpful here.

3

Hi Jay,

Thanks for the thorough questions!

Yes

Use the default map, but you need to do a pump calibration, where you will declare which pumps are slow and which are fast.

Your math is correct, however, we define the minimum bolus size to be 0.5mL. Regardless, I haven’t done significant characterization on this exact question. You could get low flow rate pumps for reservoir lagoon flow. I do know that 1) this setup seems to work well enough at 0.5V/h 2) cells will likely be growing within the lagoon at such a low flow rate 3) you should move on to higher flow rates as soon as you can

You don’t need a manifold because there is one pump per via. Instead you can use tubing splitters. epace-template code is on the github under big-e branch currently.

Best of luck! I’ll be gone for a couple of weeks by the way.