Hello fellow researchers,
I am trying to optimize the wetting procedures of microfluidic devices before using them as neuron and muscle culturing platforms. We have PDMS microfluidic devices with separate chambers for motor neurons and skeletal muscles, connecting through axonal channels. When I add liquid through the top inlet of the neuron chamber, I see many air bubbles inside the chamber and in the axonal channels. I was wondering if there is any trick to follow or any procedure, which will help me get rid of air bubbles and liquid will flow nicely everywhere. I do force in the inlet opening while I add liquid and it manages nicely to go from top inlet to the bottom inlet, but not through the axonal channels. I also add liquid in the muscle chambers to get rid of emulsions. I was wondering if there is any surfactant that will work best and will not be toxic for the cell culture. Two images are attached herewith for your convenience. Thanks in advance.
You could try to flush channels with a wetting fluid first.
We usually use 70%-100% ethanol. You could flow EtOH at high velocity (but dont burst it!) and apply pressure pulses in order to force the bubbles out of the channels (or lightly tap the PDMS while flowing). Then, you have to manage to exchange the feed from EtOH to something else (I usually change to water first, to flush out all ethanol and then change to cell suspension so that the cells dont come in contact with the EtOH). I do this by switching syringes without introduction of air (Luer-Lok works for me).
Could that work for you?
This problem arises due to contact angle variation inside the channels. The wetting of the microchannel surfaces wet at different velocities by the advancing interface.
I would absorb the fluid using a paper (capillary pump) at the outlet, let the channel dry completely and then do silanization ( wet chemistry).
I hope it helps.
In addition to Georgs answer (a procedure which is also discribed here: https://blogs.rsc.org/chipsandtips/2017/02/28/a-simple-bubble-free-cell-loading-technique-for-culturing-mammalian-cells-on-lab-on-a-chip-devices/) you could try to treat the PDMS with plasma or fill the channels with your medium directly after (plasma-)bonding them (s. https://www.researchgate.net/post/How_long_does_it_take_for_PDMS_to_lose_hydrophilicity_after_plasma_treatment).
Mrinal Das Could you solve the problem with EtoH ? Actually I am also facing the same problem. I have cylindrical micro wells for formation of cellular spheroids. I always find bubbles in my wells when I try first time perfusion with cell culture medium
Hello Fellas,
Thank you all for your feedback. Using absolute ETOH did work with getting rid of bubbles. However, I haven't used any cell suspension afterwards and therefore it is difficult to say if washing with water afterwards completely removes the ETOH from the axon channels and not detrimental. But I did not see bubbles formed in the axon channels after I added ETOH to the top inlets.
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