I had a go last night with a 12mm ID perspex tube, there was definitely a problem with the bubble sticking with pure water. I added some glycol, which helped, but still wasn't perfect. I then added some mouthwash (don't ask) which seemed to help a lot.

I am not sure if it is the surfactant in the mouthwash wetting the tube better, or the alcohol pushing the glycol out of solution so that it preciptiated out on the surface of the perspex.

The bubble seems to move smoothly over the best part of a cm when I move the end up and down less than a mm, which isn't bad.