I don't think you should send an email - it seems really unpersonal. I was told that thank you letters are just placed into your file when the schools receive them, even if addressed to a particular interviewer. That doesn't mean that you shouldn't send one though; being granted an interview is certainly something to be thankful for.
PS. For a friend of mine who applied last year, he told me to send it to the admissions office and include the name of the interviewer in the mailing address.