Telling rotation advisors that you're not joining

[Mr. Wonton]

I've unofficially decided on a thesis lab, but my other rotation advisors were awesome people, I had a great time in their lab, and I want to stay in touch with them. How do you tell your other rotation advisors that you're not joining? In person? By e-mail? A thank you card?

[beanbagchairs]

I think an email would be just fine. If you are somewhat closer to these people, pay them a visit.