No. A working prototype is not ordinarily required to file a U.S. patent application. An inventor may file before building the final product, provided the invention has been developed in sufficient detail to be described clearly and completely. The application should explain how the invention is made and used with enough technical detail to support the requested patent protection.

A prototype can still be helpful. Building or testing one may reveal alternative designs, practical constraints, additional inventive features, or improvements that should be included in the application. The key question is not whether a physical model exists, but whether the inventor can provide a sufficiently developed and technically meaningful disclosure. A vague goal or desired result, without a workable explanation of how it can be achieved, may not provide an adequate basis for a patent application.