G. Mark’s Answer
At IBM, we were required to wear a shirt and tie at all times, and any customer-facing roles required a suit as well. At Bell Labs, most engineers and scientists didn't much care and wore what they wanted. But my mentor at the time I started took me aside and said, "Look, folks here can wear what they want, but if you look at those that get promoted, you won't see anyone wearing jeans or tee shirts. Conclude from that what you wish." Now in a biomedical role, there are folks who do desk work, designs, programming, theorizing, etc., and they'll generally wear normal office gear. But if you're in a lab setting, you'll likely be wearing appropriate attire, often a lab coat. So in essence, a biomedical engineer will wear what other biomedical engineers wear in whatever activity they're engaged in. In my case, as a computer engineer, I spent part of my time giving lectures and presentations and wore a suit and tie. In long lab sessions that sometimes stretched for two solid days, I was not about to spend it in a suit and tie, for sure. Bottom line is, don't worry about it.