HI, I use 1um fluorescent particles from invitrogen for my microPIV experiments. I mix the particle solution in nanopure water. The nanopure water is sonicated for about an hour using Branson 1510 soncator. I then add a bit of Tween20 to the solution and then mix the particles into this liquid. The problem is that there are way too many tiny air bubbles in the solution. Have any one of you faced this problem and what can I do to get rid of this problem. Thanks a bunch in advance. Cheers, Vishwa