Is it possible for bubbles to exist in vacuum? In the case of a bubble, the outside pressure is less then the inside pressure. 
If that is the case can bubbles exist in vacuum? I am not sure but this should be true if vacuum has zero pressure
 A: Yes, a bubble can exist in vacuum. A bubble itself has surface tension which tries to minimize the surface area, i.e. tries to push inward. It is small compared with the atmosphere on Earth though. But in the vacuum, there is no pressure from the outside and very little pressure from the inside. Thus, the surface tension becomes significant. 
The final shape will become equilibrium with the inner pressure. If the inner pressure is too large, the bubble will simply burst. That said, the pressure allowed inside is very small  compared to the atmosphere.
A: I disagree.  If it's a true vacuum then it can't exist.  The pressure equilibrium both inside and outside will be zero, thus the surface tension would collapse it into a "drop" rather than a bubble, as there's no internal pressure to hold it expanded.
Were air to be added inside however, then things would get weird.  Since the outer pressure is zero, expansion would be infinite... Now it matters what the surface tension strength of your material is vs. the maximum expansion of air you put inside.
