When determining design inputs it is very important to consider physical and performance traits. These two aspects will determine the used when designing the device. For instance, when considering the customer needs and having portable as one, that means the device should be light weight and not too large. Some other factors that are considered in design inputs are human factors, safety, and maintenance. Design inputs lay the whole foundation for the design of the device. That is why it is critical to think of everything that will be needed in the device. If something changes halfway through, then it can change the project entirely. Design inputs ensure for a good design to be done.

https://www.fda.gov/downloads/Training/CDRHLearn/UCM529614.pdf