As many of the students stated, design inputs so usually come from research and other investigational ideas. I would like to add that some also come from doctors and other medical companies. Hospitals and companies contract other companies to provide certain parts and products. In these cases, they provide the design inputs to the contracted companies. Failure and limitations in existing products also give rise to new needs. Now a days, most products are reinvented to be more effective and efficient, these are also design inputs.