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I'm working on a project that involves finding moving particles in a solution (in my case, a syringe, or vial). The goal is to identify particles as small as 125um(micrometers), but the problem I face when I spin the container to get the particle moving, is that the particle gets stuck on the sidewall of the container, or on the top of the solution. Being that these are very small particles, I'm assuming my problem is surface tension related. The solution i'm working with is distilled water. I want to add a surfactant to reduce the surface tension, but I'm not sure what to use because I can't have bubbles forming due to the surfactant, and I need to retain the color of the solution. An idea I had was maybe some p80? Any other ideas? Also, do you think spraying the particles with a hydrophobic spray would help with anything?

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  • $\begingroup$ Particles sticking to the sidewalls is an indication that possibly there is an adhesive force between the particle molecules and the wall molecules which is not related to surface tension. $\endgroup$
    – Farcher
    Commented Mar 6, 2022 at 6:42

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Here are some things to try.

First, there are non-foaming surfactants available. They are commonly used in commercial floor-scrubbing machine solutions, where the presence of foam in the pump system would upset the pumping action. Many are hydrolyzable silicones.

Second, you could try agitating the test solution with ultrasonics, as in miniature jewelry-cleaning tanks for use in the home.

Third, there are surfactants which are used to prevent particles of dirt from settling out of solution & redepositing themselves once they have been dislodged from things like dishes, floors, and car bodies. These are called dispersion agents.

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  • $\begingroup$ Thank you for that detailed answer. I don't mean to sound like i'm just trying to get all the answers to my project here but, from doing some research on non-foaming surfactants, i found a bunch, but do you know any that have a clear color to them? $\endgroup$
    – Ali Yuksel
    Commented Mar 8, 2022 at 1:19
  • $\begingroup$ Also, what would agitating the test solution with ultrasonics do? Trying to understand the physiology behind it. test solution as in the particle? or the vial? $\endgroup$
    – Ali Yuksel
    Commented Mar 8, 2022 at 1:20
  • $\begingroup$ test solution as in the vial, the ultrasound mixes the liquid inside it. $\endgroup$ Commented Mar 8, 2022 at 4:25

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