I’ve been running some experiments (chemostat or fed-batch dosing scheme) at very low flow rates (i.e. dosing 0.05 mL once every 2 hours). I’ve been having issues where even with very careful priming of the pumps in place so there’s no disturbance, I still get significant air bubbles in the tubing between the pump and the Pioreactor vessel. Since I’m dosing so infrequently and with such small amounts, missing a dosing event due to air bubbles (since each dose is essentially one droplet from the needle into the vessel) is clearly quite impactful to growth dynamics.
Has anyone run into similar issues and found any solutions? My thoughts are to use smaller inner diameter tubing (maybe 1mm to match the dimensions for the interior pump tubing rather than the current 1/16 in) as this would result in a holdup volume only 44% as large so there is less area where bubbles could be introduced. Another thought would be to use smaller gauge needles, which with a smaller interfacial area would hopefully pinch off into smaller enough droplets, though this wouldn’t solve the underlying issue. A pump rated for lower flowrates/volumes would be great, but I am not aware of any such product that would be compatible. I would like to avoid using syringe pumps, which while having the upside of much better control to minimize dosing issues, are quite expensive and would have to be run outside of the Pioreactor software.
If anyone’s run into something similar or has any ideas, I would love to hear them!
Hi @DonalC, these look like the older silicone tubes we use to ship with the pumps? Can you confirm that? Our newer tubes have black print on them. If so, these tubes did have this exact issue - too permeable to air. We now supply different tubes, FLEXELENE 135C, that are much more impermeable to air.
Do you want us to send you some replacements? Alternatively, look for 1/16" ID 1/8" OD platinum cured silicone tubes.
Hi @CamDavidsonPilon, it definitely is the case that at least some of my pumps are using the older tubing. Do you know (roughly) when you switched over to the FLEXENE 135C? 12 of my pumps were from a February 2024 order and are definitely the older version, but 12 others are from September 2024. I have some pumps I haven’t installed from that September order and the tubing on those has black text on them like you’re describing, but the ones I have installed have been autoclaved enough times that any text has faded, so I am unsure if they are the newer type (though I believe they are based on their rigidity).
I would love to upgrade to the newer tubing - what’s the best way to place an order since the external pump tubing item on your website is per foot rather than pre-cut?
I believe we switched in late Spring, 2024. The new tubing has a different “feel” - a bit software, and more “sticky” (for lack of a better word) than the older tubing. The older tubing also never had any text. FYI Each pump ships with ~2.5 ft of tubing, so 30ft would be enough.
