Definitely follow up. I did and was admitted into my top choice after being waitlisted. You can send a email stating: “I am still very interested in joining your lab/team. Since the interview, I’ve completed x,z,y. I believe these projects have made me even more dedicated/equipped to conduct research in your lab. Please know this is my top choice program. If you have any questions, don’t hesitate to ask.”
It doesn’t have to be these exact words, but I hope this provides a framework for you. Best of luck!