It's called Loctite GO2 All-Purpose ink and it does, in fact, bind PLA pieces together.
|Loctite GO2 Glue|
When dry, it is flexible, much like silicone glue. The drying time to set is about 30 minutes and the full cure time is 24 hours.
The great news is that it can do double duty. Not only does it glue; but, it makes for an excellent clear coat that does not appear to smear alcohol marker ink.
Here's a more complete story on the IdeaRoom3D blog.
By the way, while most of the projects in the IdeaRoom3D blog are printed on an M3D Micro, the mini-blackboard project in which I create a personalized 3D printed chalkboard was printed on a Cube3. The chalkboard paint from Rust-Oleum covered the PLA very well. I tried it with a primer and without. I prefer not to use a primer in the future.