Hello ! I am presently working on a microfluidic chip aiming at capturing hundreds of cells in an array of capture chambers. To inject the cells inside the platform, we use either 1) small reservoirs filled with the cell solution (1 mL) plugged to our chip through Tygon tubing or 2) 200 µL pipette tips filled with the cell solution direclty put in the chip inlets. Both systems are then hooked to a pressure controller to create flow. However, we encounter a very high amount of cell sedimentation directly at the chip inlets, causing loss of object and improper injection inside the platform. Any ideas to overcome these problems would be very useful. Thanks !
Hi!
Cell sedimentation is a common problem in microfluidic fabricated from soft/photo lithography. The main reason is the macroscopic inlet vs microscopic channel. When cells flow from inlet, they are affected by gravity. To overcome this situation designing asymetric inlet, reducing cell-to-channel width ratio, using dual inlets, and increasing the flow rate of cell seeding can prevent sedimentation and channel clogging.
Thank you for your answer Navid, I will look into your suggestions! Cheers
Hi! You may try increasing the flow rate transiently, to wash away the sedimentation. Also, you could try inverting the inlet and outlet (if possible) to wash away the cells before starting the experiment. Good luck!
Hello Wei-Hsiang,
I already tried to gradually increase the flow rate, wihout success, but inverting the inlets and outlets to clear the chip entrance could be a solution. Thank you !
First of all you have a cell dispersion not a solution. In the latter case problem may be only adsorption.
And this is what likely causes your real problem. If sedimentation only, there must be a critical velocity to prevent any.
This also would minimize sticking of cells to walls of your device. Similar effect would be induced by turbulence by design. To minimize sticking to walls you may experiment with surface modification.
Reducing cell concentration may also help to certain degree.