You will find experts everywhere. For technical questions, there's probably a professor at Northwestern who knows the answer. For space redesigns, talk to the person who's in charge of the space or maintains it for Buildings and Grounds. At a minimum, you should know enough about the person you're interviewing to say why they are an qualified to answer your questions. They may have designed similar devices, or consulted with engineers who design device.
Experts have their biases.
One bias you often find is a preference for the status quo, things are pretty good just as they are. Another bias you'll see is a tendency to side with the device, not the user. If something doesn't work well, they'll tell you about all the problems a users have, and not what the product designers should do better. The preparations you make for an interview depend on your objectives. If you are just starting out, you want to meet with your client before you start interviewing experts.