How to respond to a company that wants specific details on implementation of my PhD research? A company approached me for an interview to explain my work, which has been published as part of my PhD. As I understand from their email, they want to understand my work so that they can use it. However, nowhere in the email they mentioned that I am going to be paid or involved in this project. How would you approach this?

I find this email strange because they are asking me to explain my work and give them information on how to implement it so that they can make money out of it without me having any role in their project. Is this normal? Should I ask to be paid?
It's not normal to work for a company for free, and I'd simply answer something like this:


  Dear X,
  
  I am glad to know that my PhD work caught your interest. I can
  provide more information under a suitable consultancy contract.
  
  Kind regards, 
  
  L222


Note: We don't know the content of the company's email and, as some have remarked, the above response might be a bit too sharp, especially if their attitude is not so exploitative as I assumed. A milder approach, which I like, is that outlined in Dan Romik's answer. Since only you can read the email, I strongly encourage you to consider carefully both approaches, regardless of the accumulated votes.