Yep, once it's done it can just navigate to the nearest acetone reservoir in the body.
1. If you had read/comprehended the article you would understand how they plan to address this concern.
2. Really, even without reading the article, your comment just shows a failure of imagination. It's really not hard to see how this early prototype might be developed into more mature, useful applications.
Demoing that you can (partially) dissolve something in acetone or even water is not terribly impressive, even if their self-folding and mode of locomotion is pretty cool.