I believe it is important to directly quote the FDA about design inputs (ISO 13485:2003)

Inputs relating to product requirements shall be determined and records maintained. These inputs shall include:
a) functional, performance, and safety requirements, according to the intended use,
b) applicable statutory and regulatory requirements,
c) where applicable, information derived from previous similar designs,
d) other requirements essential for design and development, and
e) output(s) of risk management
These inputs shall be reviewed and approved.
Requirements shall be complete, unambiguous, and not in conflict with each other.

Design inputs are very broad because every indivdual that may be on the team has different ideas.
An example could be :
-how much life span will this product have?
-who are our customers?
-what are the safety factors?
To me these are a few questions that I believe should be asked , because it makes an impact on the design concept and will help it a little more.

In my opinion, if you were to write a document on how to make a device, and give that document to someone else, they should be able to build an exact replica without coming back to you for questions. This is the basis of a design input or requirement. Each requirement would describe a component inside the device. It would list things such as the material it is made of, dimensions, electrical connections (if any), tools made to shape or assemble the component, and mechanical properties. The requirements should also include tolerances. For instance, if I say that a component in my device should not exceed 4 lbs, I also need to include an acceptable tolerance that would not hinder the effectiveness of my device (i.e 4 lbs +/- 0.1 lbs). In sum, this document is almost like a recipe to building your device. Without it, major safety issues can arise if the design of the device is not well defined.

Design Inputs make up of higher level requirements, that trace to Design Outputs which is a more low-level specific requirement. One way to maintain their inputs is the Design Input Document, that is maintained in the DHF, which Quality can refer to.

However, I was wondering if those of you in a medical device company, maintain these Design Inputs and Outputs requirements in a specific type of software that shows the traceability within a design matrix.

Design input is the key point of medical device. If design input defined well during product development, it makes the rest of product development easier. Some sources state that establishing design input can take easily up to 30% of the project timeline. Sometimes people are in a rush to get the product to market and give very little time to design input process. I think to spend a little extra time on design input process can save money and time on long run and minimize the chances of product recall. Goals of the design input should include user needs and intended use, safety, be clear and objective, comprehensive, device functions, reliability, regulatory requirements, labeling and packaging, limits, compatibility with other devices.

Source of design input is the market research of the product. What it is that is needed. From this you can figure the customer needs. Once the customer needs are set, it is easier to plan design inputs. For an example, if you are working on a project that requires to find a movement of brain while it is hit with an object for impact testing for automobile, one of the design inputs would be using accelerometer and being specific about what kind.

Deepthi, yes it is a common practice to keep these inputs and specs in an excel spreadsheet as part of the Design Requirements Matrix (DRM). This document may even be a live document that can only be seen by those on the design team and can be modified accordingly. In my recent experience, the DRM for a specific project has been posted on Sharepoint online for those on the team to comment on the inputs, specs, record meeting minutes, and make changes after the meetings.

Your goals when defining Design Inputs include:
Capturing all functional, performance, safety, and regulatory requirements.
Build upon User Needs and intended use.
Make sure Design Inputs are clear and objective.
State Design Inputs in a way that allow you to prove / disprove them.

You also should consider all sorts of other sources to help you define Design Inputs:
Industry standards
Regulations
Previous projects / products
Competitor products
End-users
Prototypes

This are sources which would help us find specific design input specification.

As Adrian stated above, past projects are a source of design inputs. To expand on this, the Design History File (DHF) of other similar projects would be a source of design inputs. The key to choosing design inputs is to find something that satisfies the customer but is also practical. The customer doesn't have the history of designs that failed or why they failed. Its your job to look at similar projects and if something that the customer is suggesting failed before, don't use it. You have to take the customer's wants into account but as an engineer, it is imperative that you put practicality into account first. When I say practicality, I mean pure science, safety, and most importantly things that you might not have thought would be an issue or lessons learned from past projects. This information would be in the DHF of these past projects and would be a great source of design inputs.

I think design input can come from many sources including customer/client requests or observations, team members raising their own observation. Design inputs are defined allowing development to proceed after ensuring that all the requirements have been met and that the product has its desired function, and is safe to use in its intended function, and any similar previous designs. Having a good foundation of design inputs can help the development process of the medical device to flow more efficiently

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

In our senior design capstone project for BME, the design inputs were developed from two sources: market research and customer needs. In order to develop design inputs, market research was conducted in order to understand what products and devices exist on the market to fulfill the given need/function. Secondly, customer needs were taken into account to help flesh out a product that would stand apart from the existing competition. These were the primary considerations when developing design inputs. Other considerations, such as disposal, safety, and regulatory conditions will also be taken into account when developing the design inputs. Lastly, cost will also place constraints on design inputs.

Design inputs are the foundation of medical device development. And without a strong foundation, bringing a new product to market can be problematic.

Call them what you want (design inputs, design requirements, design and development inputs, etc.), getting your design inputs right is the most important thing you can do to make sure your device is developed correctly.

I know it’s tempting to rush through device development. Once you have a great idea and you have a prototype that works, you just want to get the product to market as quickly as possible.

But, there are several steps along the way where it’s good to slow down. Design inputs is one of those times.

According to the FDA’s design controls guidance, design inputs can take up as much as 30% of the project timeline for complex designs. This means that if your timeline is 12 months, design inputs should take at least three months to define.

That’s a good thing to remember. Taking a deep breath, slowing down, and getting design inputs right the first time will only help the rest of development.

Defining Design Inputs
In a nutshell, design inputs define all the performance criteria, requirements, and features of your product. Primarily, you should pull from your user needs to define the design inputs.

However, there is a key difference between user needs and design inputs.

User needs are abstract, using words like “easy,” “better,” and “simple.” This is a good way to state user needs, because it keeps things broad enough to tweak during the process.

Yet, sometimes we either trivialize or do not invest much time defining user needs. Keep in mind that these user needs are a precursor to the design inputs. User needs are a starting point for building the foundation of your medical device.

With design inputs, it’s time to get concrete. They should be objective and measurable, not abstract.

My advice is to make a first pass at defining all the design inputs for your medical device. While words like “easy”, “better”, and “simple” are too subjective and cannot be measured, your first version of a design input may include one of these types of words.

Keep in mind defining Design Inputs is often iterative. The first iteration is likely to be ambiguous and vague. It is your job to figure out how to define these so that all are clear and objective.

A good practice is to make a prototype and to do some informal bench testing to help make design inputs clear and objective.

There are a few goals to consider while approaching Design Inputs:

Capture all functional, performance, safety, and regulatory requirements
Build upon user needs and intended use
Make them clear and objective
State them in a way that allows you to prove or disprove them
Defining great design inputs is an art form. You may recognize great design inputs when you see them, but it will take time to train yourself to produce them.

Remember to give yourself and your project plenty of time during this phase.

Sources For Design Inputs
The user needs you’e already defined should be the primary source for your design inputs, but they can’t be the only one.

And no one person on the team should have the sole responsibility for design inputs. When a team is involved, you get everyone’s experience and opinions, which will make the effort stronger.

Besides user needs and the team, there are several more sources you should consider while defining design inputs:

Industry standards
Regulations
Previous projects or products
Competitor products
End users
Prototypes
This list isn’t exhaustive, but it’s a good start.

Your list of design inputs needs to be comprehensive. You need to consider all aspects of the medical device you are designing and ensure that you have defined all design inputs. This means capturing everything — all criteria about your product — what’s important, how the device should perform, and so on.

Remember, some claim design inputs should take almost a third of a project’s timeline.

Think of your design inputs as a contract of sorts. This “contract” lays the groundwork for medical device product developers. The engineers and designers responsible for developing the medical device use the design inputs as the criteria.

Becoming A Design Input Artist
Remember that everything you establish during your design input phase will have to be proven during design verification.

Design verification proves you designed your medical device correctly. You should always consider this step during design inputs, and write your inputs in a way that makes them easy to verify (or at least as easy as possible) when the time comes.

Defining a comprehensive list of design inputs is one thing.

Defining a comprehensive list of design inputs which can be easily proven as part of design verification is a whole different thing. Having the ability to establish design inputs with design verification in mind is definitely an art.

Let me elaborate.

Earlier, I shared that it is a good idea to do some informal testing to help define clear and objective design inputs. In addition to helping you with design inputs, the informal testing can also help you establish test methods for design verification purposes.

Just one word of caution about design verification and testing.

Remember that design verification methods include testing, inspection, and analysis. Sometimes a design input can be verified by means other than just testing.

Including Acceptance Criteria
You need to define criteria for features of your medical device so that you know the product performs as expected. This is referred to as acceptance criteria. Regulations mention the need to define acceptance criteria (usually as part of design outputs).

It is my opinion that when you define clear and objective design inputs and keep design verification in mind while doing so, you will instinctively include acceptance criteria as part of this process. And including this as part of design inputs is perfectly fine.

Design inputs will make or break your project, and mastering the art of writing good ones will take some time.

But doing it right will set you up for a very successful product development.

Design inputs are critical to medical device development. The design requirements can be a document that can prove if the product will have issues or not. Usually, products that result in failure is due to faulty design inputs. The design input acts as the foundation of the product. The manufacturer needs to establish design requirements that take the customer needs into account. There must also be a system in place to look through when there are conflicting requirments or flaws in the design. The names of those who approved the requirements should also be on this document. The inputs should be clear and objective.

https://blog.greenlight.guru/defining-design-inputs-and-design-outputs

Each manufacturer is responsible for establishing and maintained a procedure to ensure that design requirements relating to device are appropriate and address the intended use of the device. The design input requirements should be documented and approved by a designated individual. The input should require the functional and safety requirements, regulatory requirements, information derived from previous designs, and outputs of risk management. So, essentially the design inputs are very important for the making of the device. Although most people want to get their product on the market very quickly, I think more time should be spent on the design inputs and requirements since it is so important. The design inputs should take up around 30% of the project timeline. This is essential as it will build a strong foundation to ensure an easier and smoother path to market the medical device. Some good sources would be to obtain advice from a superior or those familiar with the design of your product to really ensure that it is feasible to create this project and for it to actually work effectively.