How can I do this? Maybe some sort of oscillator? What would you recommend?

soap

Why does it decrease the surface tension? Also, what else, possibly a mechanical device would create the desired effect. Additionally, what other solutions would significantly decrease the surface tension of water?

Google the difference between adhesion and cohesion.

Are you trying to say that soap, or any other solute, when added to the water mixture, will decrease the surface tension? Is this because the cohesive forces of the water decrease due to the presence of a contaminant/solute?

There is a decrease in cohesive force between water molecules !!

 

when soap dissolve in water , water molecules form hydrogen bonds with the soap molecules ..

 

As a result there is less hydrogen bond formed between water molecules !!

 

Hence the cohesive forces between molecules decreased !!