Not a PI, but an undergrad researcher (author on the poster) in the School of Medicine's Dept. of Biomedical Sciences
Will be presented at the University-wide Undergraduate research presentation/symposium on a weekday. Undergrads stand in front of the poster and look pretty and answer questions when asked, while other students and faculty members walk around. Not a competitive environment
Didn't want to embed as I posted this pic already but this look is what I was thinking of wearing (OCBD shirt, just not buttoned down in the pic)
I'd wear that. You're at your school among colleagues and friends. No harm looking sharp. No one is going to chastise you for being overdressed.