Let me endulge in my creative lience, but it's not a Soap Bubble gun, it's a "Super-Reactive Bio-Chemical Gas Sphere Launcher". It fires off an unstable gas that effects organic tissue. The gas is trapped inside of the thin Bubble shell, which is actually a super-dense polystyrine carbon tubuiral mesh. Using Buckyballs in this elastic material's atomic structure, the sphere has amazing strength and yet is increably light. This allows the bubbles to also be shot at a high speed, only breaking on their target, and releasing the quickly desolving gas into the victem's body and/or circetry. (If your victem is a robot)
The Alt-Fire is more like a large glob of just the Polymer shell, or basically the plastic bubble. The gas is reducing to a more stable structure. The gas has almost anti-gravity properties when activated on impact, causing the victem to float skyward inside a bubble of this gas.
(BTW, you CAN pop the bubble, by using the same weapon that made it. Just Alt-Fire another bubble, and the two will overwhlem their internal resistance and explode.)
So the weapon fires hot plastic bubbles full of "Funny-Gas" that does nasty things, understand? It does NOT shoot soap bubbles. Please pass that on!