Design and Development

Are you a student or researcher making an invention into a medical device? Then read this article and contact us for more guidance. We can support you with the Design and Development (D&D) process from a distance using email, Skype etc.

When to start with the Design and Development process? Soon after, you decided to develop a medical device for the market.

This article guides you through the first steps of D&D. Let me know your comments, and you can always re-read the article on our webpage.

The D&D process is often depicted as shown below. The first time I saw this, did I immediately know where to start with the D&D process. Well….. no. These pictures are only helpful when you already understand the process, not to get to understand the process.

Below I will discuss all steps and words used in this process flow diagram. At the end of the article, please look at this picture again and see if it makes sense now.

Al steps and phases below should be documented (Good Documentation Practice), reviewed and signed like any other QMS document. The design plan (= an input) defines if certain stages or reviews need to be finished and approved before continuing to the next step. An obvious one is that the design verification should be completed and reviewed before moving on to design validation.

User Needs

The first term we need to discuss is User Needs. Users can be (but not limited to) the patient, the surgeon or nurse, therapist or combinations thereof. The user needs to describe what they would want off the product. Biocompatibility capture the user needs. The user needs are formalised in the user requirements. User requirements are defined by interviewing the users are required. The User Requirements should consider (but not limited to) the following topics:

  1. Purpose, goal, the effectiveness of the device
  2. Safety (electrical, biocompatibility, breaking, sharp edges, irradiation, etc. )
  3. Material (maybe not the exact grade, but descriptions as plastic, soft-touch, degraded within three months etc. )
  4. shelf life, active life
  5. Packaging (single or double packaging, carton boxes, number of products per box etc.) and labelling (which information, QR or bar-codes)
  6. How is the product maintained, repaired, disposed of

Be aware that you must write down the user requirements from the user point of view. These are not technical requirements. User interviews are therefore vital. The user requirements are translated into technical requirements as INPUT.

Design Inputs

Defining the design inputs is a task and cannot be done in a few hours. Make sure that your design inputs are clear, objective and stated in a way that allows you to prove them. Keep verification of the design inputs in mind when defining them.

  1. User and Technical Requirements
  2. Statutory and regulatory requirements
  3. Relevant information from previous designs
  4. Design and Development Plan (kind of project plan)
  5. Regulatory approval plan, including (or separate) clinical trial plan
  6. The output of risk analysis
Design inputs must be clear, objective and stated 
in a way that allow you to prove them

A larger team should collect design inputs with a broad range of experience and specialism (design, electrical, process, material engineer, marketing/sales, clinical trial experts etc.). Sources to define your inputs are the user needs, experience with prototypes, competitors products, previous (older) products, industry standards, etc.

Design Process

When the user needs and design inputs are defined, the actual design process can commence. Standard project management rules apply to ensure that the design process is effective, efficient, controlled and on time. The project manager must organise regular team meetings and design review meetings to ensure the project is on the right track and no design creep occurs.

Design Outputs

Outputs are verifiable results related to the input characteristics of the product that are essential for its safe and proper use. The output of the D&D process results in the specifications for purchasing, production, and service and reference to the acceptance criteria. Outputs can be

  1. Design drawing with all its dimensions of the semi-finished parts and the final product,
  2. Product specification of semi-finished products, assemblies, sub-assemblies, and finished products,
  3. production procedures of all (intermediate) steps, assembly, packaging, etc.

Outputs will be the basis for the Device Master Record.

All the (in-vivo and in-vitro) tests are NOT part of the outputs.

Design Verification

In short, the design verification is the proof that the Design Outputs meet the Design Inputs. This verification is done in the form of testing. The following types of testing are possible.

  1. Prototype testing on devices that resemble the final product. Development testing on materials, models, etc., is vital to determine the design, but not verification testing.
  2. Proof testing is also done on prototypes, but instead of testing to specifications (as done in prototype testing), the tests are to test the product to failure. For example, how far can you bend, load, pull the device before it breaks—important testing for warnings and warranties and input for risk analysis.
  3. Acceptance testing is done to define if the production of your products is good. These can be tests on all products or a selection of the products produced. Preferably these tests are non-destructive but not always possible. Validation of the production and the acceptance criteria and testing is also part of the acceptance testing. More information on Validation can be found in a previously published article.

Within all three of the above-described testing groups, different tests can take place: visual inspection, in-vitro testing (e.g. analysis, mechanical, electrical, software, ageing, degradation testing), in-vivo testing (biocompatibility, implantation studies) and all other studies required to establish that the design outputs meet the design inputs.

To keep an overview of all design outputs and inputs, a design traceability matrix can be used. This is a table listing the user needs, the inputs (short description or, if possible, target value with tolerances), references to input documentation, standards (e.g. ISO norms), regulatory documentation, SOP’s etc.). The same for the output, short description or average values and standard deviations and references to documentation (e.g. drawing). The verification is a tick-box, confirming that the input is meeting the output. The tests results can be listed in the reference section.

Design Validation

The design verification links the design outputs to the design inputs. The design validation relates the final product (the medical device) to the user needs. The most general design validation study is the clinical study. However, this is not the only study possible or required study dealing with the ease of unpacking products, re-sterilization, repair, maintenance, disposal, etc. Or, in short, all studies confirming that the medical device meets all its user needs.

As said, the clinical study is one of the essential design validation studies. This is valid for all medical devices. The medical device regulation (MDR) requires more clinical evidence to prove the efficacy and safety of a medical device. What is sufficient clinical evidence? This should be defined by the manufacturing (and reviewed by the notified body) and aligned with sales, lifetime device, target population, benefit, cover risk (residual risk from the risk assessment), foreseeable misuse, state of the art.

Design Review

A good design review has several positive effects. It ensures all team members, management and customers are up to date on all aspects of the design. It also ensures that all contributory factors and design aspects are taken into account to ensure that the design fulfils the Design Input.

A design review team consisting of the design team and non-team members (subject matter experts, customers, management, partners etc.) should regularly review the design. At least at all stages of the design and development process, as the figure above suggests. In the design review, one should review all changes of a previously reviewed stage (updates in design inputs, for example).

Further, it is very well possible that more than one design review is planned during the design process. This is depending on the duration of the development process and the complexity of the device.

Design Transfer

Not part of the overview figure from the beginning of this document, but part of the Design and Development process is the design transfer. this is the action of transferring knowledge from the design or development department to production. Usually, this starts when producing devices for the clinical trial. These devices should be produced under ISO13485 / GMP, and therefore operations need to be trained, need information (specifications, instructions etc.). The design transfer is concluded after design verification, commercial standard production starts with an approved and validated product, as changes in design can happen due to the clinical study.

The collection of all documents produced during the design and development phases, specifications, inputs, tests, analysis, observations, and not the final version, but all revisions of these documents, is the design history file, the basis for the design file or technical file, which need to be reviewed by authorities for market approval.

About Sandra de Vos

Sandra de Vos has been working with (polymeric) medical devices for over 12 years now. She has set up Quality Management Systems (QMS) from scratch to ISO 13485 certification. Sandra has experience with product and process development, including DHF files, Risk analysis and process validation. She is a certified Lead Auditor.

Currently, she is the founder and CEO of Vosfox Medical. Vosfox Medical offers consulting services and contract manufacturing services (CMO) for medical device companies.

Our CMO services include using our facilities and support to develop the production process and make it ready for clinical trials. We offer ISO Class 7 cleanroom, QA support, production process development and validation support, etc. We have several 3D printers in the cleanroom, and we produce medical-grade filaments (for FDM printing).

You can stay as involved as you wish and outsource what you want.

Please visit our website (, mail me (, or call +31-650281838. You can also comment on the article and help me improve this and future articles.