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No air into capillaries!

  1. Oct 15, 2009 #1
    I didn't know where to put my thread so I hope this is the good place.
    I have a technical issue concerning capillaries! I use capillaries to fill a mircofluidic network and I am desperately looking for a way to prevent air from coming inside capilarry and thus coming inside my microfluidic network once I have filled my microchannels!

    I am not an expert in capillary forces so I would hope someone give me a solution or at least explain to me why air come into the microchannels when the capillaries nds are open.

    Thank you
  2. jcsd
  3. Oct 15, 2009 #2


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    It's hard to say without knowing what the set-up looks like. My first thought is simply to leave your capillaries submerged in the fluid. Secondly, cap them with something like putty before removing them from the fluid.
  4. Oct 16, 2009 #3
    You can use a small syringe and an adapter to pump the fluid into the column. For small capillary, submerging only can not suck in the fluid totally.
  5. Oct 16, 2009 #4
    In fact i have a pump with two inlets and two outlet but I only want to use one inlet and one outlet. I cannot shut the useles inlet and outlet because the pump is not self priming and thus I have to fill the pump and then close the inlet and outlet because I don't want any liquid to come in or out by these two directions.

    I have been thinking really hard on this and if i just close the capillaries linked to these two holes I will trap bubbles into the capillary that would be able to go in the pump which I don't want. And if i stuck the capillaries with an hydrophobic material will the air trapped in the capillaries stay close to the hydrophobic material? I am quit doubting about the feasibilityof this. I have a second concern: if I stuck the end of the capillary linked to the inlet and then cut any contact with outside will the liquid in this capillary be pumped in the microfluidic channel?

    Sorry for bringing more questions and thanks for your answers!
  6. Oct 16, 2009 #5


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    I use a capillary (80 um diameter) and 0.006" tubing in my research, and need my system to be absolutely bubble-free. I've gotten good performance from the Upchurch's V-101L valve, which I use to seal off the system when it's filled with liquid. Have you looked at / tried any of the valve selections from Upchurch?
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