Design inputs are the foundation of medical devices, and so without a strong foundation it would be difficult to bring up the whole product. In a nutshell I would say that design inputs define all performance criteria, requirements, and features of the product. Some goals to considered are: Capture all functional, performance and safety requirements. Build user needs. Make clear objectives. State them in a way to prove and disapprove them. User is a primary source. Several other sources are: Industry standards, regulations, Previous projects products, end users, prototypes etc.