I'd say it depends. The first lab I worked in was at a very conservative institution, and my meeting was a more formal interview-type meeting, so I wore dress pants, dress shoes, dress shirt. I fit in well enough but, honestly, I don't think I would have been out of place in a suit.
The second lab I worked in was at my school, and it was more of a casual "yeah, sure, stop by my office whenever you get a chance" type of meeting. I don't recall what I wore, but I'm pretty certain I didn't wear a dress shirt. If I were to guess, I probably wore jeans and a polo. Whatever it was, it was WAY more casual than dress shirt/tie (it might have even been shorts 😱😱😱😱😱😱 but probably not). A shirt and tie would have been overkill. I'd say "dockers" and a polo would suffice.