It was a good interview. They focussed mostly on my research skills and conceptual knowledge related to the proposed research work. They asked many questions related to experimental work. Then, at the end questions were asked from motivation for the PhD position and future scope after PhD.

The departmental interview is just one round with three interviewers. In my case only one professor is really close to my research but that almost happens to everyone because not all professor you have on your list will be available. The professor who's working in my field asked more technical questions and details about my past research project, whereas two other professor mainly chatted me through their life experience and why they think MIT is a good place to go.