Do I need a prototype to apply for a patent? And if so, does the prototype have be of the same material as finished product? Or can highly detailed cad drawings do the job?
No, making a prototype (actual reduction to practice), as filing a properly prepared patent application is considered "constructive reduction to practice."
United States patent laws do not require you to have a prototype in order to apply for a patent, all that is required is that you be able to describe the invention so that others could both make and use it. So while you do need to have some kind of identifiable embodiment you can start by proving your concept on paper. (IP Watchdog)
And from the USPTO:
Reduction to practice may be an actual reduction or a constructive reduction to practice which occurs when a patent application on the claimed invention is filed. The filing of a patent application serves as conception and constructive reduction to practice of the subject matter described in the application. Thus the inventor need not provide evidence of either conception or actual reduction to practice when relying on the content of the patent application. (MPEP 2138.05)
NOTE: This is not legal advice. Please consult with an attorney.