How to control the particle tension?

[anulagarwal]

Hi,
I am trying to implement a mechanic where using a sweeper/cube in Unity, I clear out the liquid and collect it in one corner.
So If the liquid is splattered across the floor, i clean and collect the liquid in a corner using a cube. 
However while doing so, a lot of small particles just pass through the cube move really fast, How can i make the liquid thick and not separate from each other so easily?

Thanks