Have you ever worked on a group project where it just feels like not everyone is pulling their weight? Maybe all the work is falling to one person—maybe that person has been you! This near-universal experience, it turns out, is also shared by mice, as Emory PhD candidate Jari Javier has discovered at the Murugan Lab here on campus. Mice, with their complex behavioral and social hierarchies, are great stand-ins for studying human social interactions like the neuroscience of group behaviors.
It starts pretty simple: put a mouse in a box where they can push a button and get a reward. (In this case, the reward is sugar water—sweets being beloved by all.) Once all the mice have learned that this is how the box works, you put three mice in the box. Then it gets interesting: what ends up happening is one mouse (the Worker) is doing all the work of pushing the button, but the other two mice (the Parasites) camp out near the sugar water dispenser reaping all the rewards.
Why do the mice settle into these categories of Workers and Parasites? The team at Murugan Lab set out to explore whether social hierarchies such as dominance could explain why some mice become Workers and some mice become Parasites. To test this theory, they developed a urine-marking test: place two mice in a box with absorbent paper, physically separated by a divider, and observe where they mark with urine. More dominant mice will mark closer to the divider (and the other mouse’s territory).
When labs such as Murugan develop tests for their subjects, there’s not necessarily standard equipment available to purchase that will suit their exact needs—so there’s a lot of creativity and tinkering to get the right setup. For this test, Jari needed a contraption that would separate the mice but still allow them to interact with each other, and be sturdy enough that the mice couldn’t knock it down. The mice also liked to tear up the edges of the absorbent paper, so some kind of barrier was needed to keep them from destroying the test material.
Enter 3D printing, and the ability to design a three-dimensional object to your exact specifications and then print them out. Undergraduate students at the lab, Emily Chen and Joshua Kho, designed several iterations of a system of interlocking parts to separate the mice during the urine marking test, and also keep them from tearing up the paper.
They printed their prototypes and final product on the PRUSA 3D printers at the WHSC Library, conveniently located a short walk away from their lab. After all that tinkering, the 3D printed parts fit perfectly in the standard mice container that many labs use. With 3D printing, the team is able to print more dividers so they can run several instances of the urine marking test at once.
And because the print fits the standard mice containers, other labs might find this to be a useful tool—so the Marugan lab plans to make the plans for this print freely available so other mouse labs can use them as well.
What are the preliminary results? Well, so far it doesn’t seem like dominance and social hierarchies can quite explain why some mice become Workers and some mice become Parasites. So the experiments will continue.
We love seeing how you’re using our library resources, whether that’s books, articles, or 3D printers! If you have a story to share about how you’ve used 3D printing for a project, let us know in the comments!