De-Risk Your Medical Device Project with Targeted Prototypes and Mock-Ups

Effective prototyping can significantly reduce time to market and overall development cost.

Michael Kahn, Director of Firmware/EE

June 24, 2021

11 Min Read
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Non-form-factor test bench to develop and refine key elements of optics and electronics.Image courtesy of Product Creation Studio

Appropriate fidelity, type of prototype, and mock-ups can answer the right questions about a new design quickly and efficiently, at the appropriate phase in a product’s development cycle. Using this approach early in the design process can minimize development cost and schedule, ensure product performance, and make sure that all user needs are met.

A prototype can efficiently answer key questions about a new design, as long as the team considers the appropriate type of prototype and fidelity for the given development cycle. This can significantly reduce time to market and overall development cost. For example, pre-screen testing on an early circuit board prototype that may not be constructed with final materials or processes can streamline the regulatory submittal/approval process later. If the prototype is good enough to assess compliance with relevant regulatory requirements, the data gathered will be hugely valuable in the subsequent design updates.

Prototypes and mock-ups can range from full feature-complete devices that perform like the end product to mock-ups of specific design elements that validate aspects of user interaction, brand language, or a specific aspect of the technical implementation. It is not always necessary that the prototype or mock-up be constructed like the final product—3D-printed plastic parts may serve adequately, instead of very expensive tooled molded plastic parts.

Enhanced Design Performance

Design performance is often enhanced by discoveries and optimizations that can be easily implemented early in the design cycle. Changes made at such an early stage are not constrained by other portions of the design that have already been completed or by a large stock of components intended for production that would have to be scrapped to make a change. Here are some examples:

  • Example 1: Late in the development cycle on a design for a laboratory diagnostic device it was discovered that, because of an incomplete consideration of physical layout needs, end users would be forced to blindly access a key test port because of poor placement of the display and controls. Having a clear line of sight for proper positioning and alignment is critical for obtaining valid diagnostic results. Validating the physical layout by using a cardboard mock-up to test interaction with actual end users would have found this problem sooner and avoided several months of re-design. Using simple cardboard mock-ups allows for observation of how real users would interact with a device, uncovering nuances that would be easily missed with a dry workflow analysis.

  • Example 2: Picture a situation where you have already spent $200,000 and eight weeks of tool fabrication time to make the production enclosure and then discover the design does not meet the “showstopper” requirement of lasting an entire shift without needing to recharge the battery. This shortcoming could have been discovered much earlier while testing using a 3D-printed enclosure, when it would have been a simple change to modify the enclosure design to support a slightly bigger battery. Now you must choose to either go to market with a key defect or take a schedule slip and incur both the cost and time to modify tooling, re-design electronics, or scale back desirable performance features such as the brightness of the display to use less power.

The cost of a design change increases dramatically the deeper into the development cycle the change is made because:  

  • More supporting design elements impacted.

  • More development time invested to get to production fidelity.

  • Increased labor cost when a large development team assembled in later stages of development is stalled by a portion that is not working.

  • Purchased production components and material are scrapped.

  • More support infrastructure impacted such as test fixtures, test procedures, and supporting software.

Cost impacts for late design-cycle changes vary widely based on the size of the project and the number of assembled team members. Consider the case where other members of a development team get stalled because of a complex electrical hardware piece that requires three extra months to get working before being able to support software integration. At this point in the project, it is likely that an assembled team of at least several software engineers and mechanical engineers is also delayed. Cost impact would be in the realm of over $100,000 in labor inefficiency from other dependent practice areas not being able to complete their work until this problem is solved. However, developing a complex technical piece ahead of time and utilizing a small or single-person team prior to project start-up results in a validated, working “building block” and allows a more deterministic schedule, especially in cases where a large cross-discipline team is needed for development of the product.  

Pre-Product Development Prototypes

Product Creation Studio often becomes involved prior to product development to refine and validate product vision, ensure market and business feasibility, de-risk or define technical functions or elements, and validate technical feasibility. Such early involvement often entails collaboration among marketing, product management, industrial design, and engineering teams.

Sharing physical prototypes/mock-ups often improves engagement and decision-making with stakeholders and intended end users to obtain critical inputs to tune and validate market requirements and needs, as well as to assess product viability. These are often in the form of physical nonfunctional form-factor prototypes, but can also be low- or high-fidelity sketches. Examples include:

  • Product shape models at various levels of fidelity and finish to validate aesthetic form and feel and balance when holding.

  • Full cosmetic models that allow evaluation and refinement of aesthetics and visual brand language; some models can incorporate functional elements such as lighting, buttons, and sound.

  • Interaction mock-ups that evaluate usability and workflow; these can be low fidelity and only model portions of the product that need to be assessed for usability.

Technical elements required by the product that are undetermined and complex, have a high risk of iteration, require extended development effort, or may not even be feasible to implement within the product constraints need to be built, tested, and validated prior to integration into a product. This enables a more-deterministic product development schedule and project plan.

Pre-product prototyping can take many forms, such as a benchtop system using off-the-shelf or custom components and lab equipment to test key components, applicability of technology, and pre-develop complex algorithms.

How much time this stage takes depends on the product and the technology it requires. A product that fills an entirely new need, where nothing else like it exists, will take more time to validate viability, user needs, and other features—for example, the first portable MP3 player. A product that requires leveraging new technology or developing its own new technology would need considerable testing time up front to ensure performance and viability before using it as a component in a product. Depending on the level of risk, modeling would be done prior to product development—for example, if it is a “must-have” to hit a certain form-factor, we would identify key components and rough out a 3D stack-up to make sure the form-factor is feasible prior to starting a full product development effort. If it is a lower-risk scenario, this effort would take place as a normal part of product development as part of the architecture phase—an early product development phase prior to starting the detailed design of custom components.

Early-Phase Product Development Prototypes

Once product development starts, early product development activities capture and validate product requirements and explore industrial design and implementation options. Building upon pre-product development results, this product development stage defines the architecture and selects key materials, components, fabrication methods, and finalizes the industrial design. These activities are predecessors to performing any detailed design work, such as developing actual form-factor electronics and enclosure components.

If a specific small form-factor is a key requirement, extra time would be spent mocking up in CAD a detailed stack-up of place-holders for internal components to ensure the form-factor is feasible. If look, feel, aesthetics, and visual brand language are of key importance, extra time and effort needs to be spent creating non-functional aesthetic models that match color and materials to validate the look and feel expected for the final product.

Validation is often an active task with focus groups, usability studies, and analysis. New discoveries that result in a change of requirements do happen during development; however, time spent up front validating requirements can reduce the occurrence and magnitude of costly, mid-stream design changes. In the architecture phase, key technical component “building blocks” are finalized. This may require active testing by prototyping portions of the design if further work is needed before being used in the final design. In addition, building and testing of non-form-factor development boards may be warranted if there is a high level of technical uncertainty.

What is most important in this early-phase work is having a clear understanding of unknowns or key risk areas that must be resolved prior to progressing into detailed design activities. It is often more effective to get out of a dry analysis mode and to design experiments and build mock-ups in order to actively test assumptions and enable faster discovery. 

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Product Development Prototypes

In the later phases of product development activities, engineers capture the detailed design for custom components such as custom circuit boards, embedded software, and internal and enclosure custom mechanical components to fabricate, assemble, and test prototypes. Following detailed design activities, product development phases specify and validate production component fabrication methods and develop and validate manufacturing assembly processes. 

Because iteration and tuning are expected, early prototypes are often fabricated using rapid prototyping materials and fabrication methods that keep the cost of changes as low as possible until performance features are fully vetted. Even though a first or early prototype may work and look close to the real product, there is often considerable development effort that is still needed to get from the initial engineering-built prototype to production-ready specifications.  

Early prototypes are built to test and validate implementation decisions that can meet the product's functional and performance needs. In a new complex circuit board design, for example, portions of the circuit design may require debugging and reworking to function as intended. Once functional, due to the complex interaction between embedded firmware and hardware, design changes may be identified to optimize integration. Early mechanical enclosures and parts are built and checked for fit, function, and ease of assembly. 

A prototype can be built quickly and efficiently using 3D-printed or machined material that can be rendered in a few days, versus a molded plastic part costing tens of thousands of dollars and weeks to complete and deliver.

Several rounds of form-factor prototyping at different levels of fidelity (compared with the production version) are often required to validate key design elements of the product design in a systematic way. This is a cost-effective, efficient approach to tune the design for function, performance, safety, compliance, and manufacturability.  

Experienced manufacturers and product development teams use a set of acronyms that relate to the prototyping stages:

  • EVT (engineering validation test) to validate that the product design meets the performance requirements for intended use.

  • DVT (design validation test) to validate mass production component fabrication processes and test product performance requirements.

  • (PVT (production validation testing) to develop and qualify the final assembly processes and validate the assembly process.

The first EVT prototype may look and work like the real product, but it is far from being a production-ready design with further development still needed to tune performance and function, develop the production process for its key components, and ensure the design can be manufactured efficiently at the required level of quality.

Trading Quality for Speed Is Risky Business

Companies often feel pressure to get a product to market as quickly as possible and sometimes struggle with the cost versus value decision. Is it worth taking a seemingly less direct approach of developing mock-ups and prototypes to answer key unknowns, de-risk technical elements, and validate user and market need assumptions? Do engineers build a product with enhanced characteristics that better meets the needs of the end user, or design something less detailed to get it to market faster?

It is a struggle, even for a seasoned product development leadership team, to make the appropriate trade-off up front: pre-product de-risking work versus the often-critical need to get the product to market quickly. Targeted prototyping may seem like it adds time to the overall development schedule; however, if the non-vetted portion of the design is later found to have negative impacts on the development schedule downstream, the cost becomes much greater. Consider the following real-life examples:

  • A home-use therapy device that was an aggressively small form-factor was locked into an expensive electrical and mechanical detailed design effort. When built and tested on real humans, it did not maintain a reliable contact. Early form-factor mock-ups would have enabled fast and low-cost interaction to identify the needed adjustments in form-factor features.

  • The manufacturer of a new therapy device moved into product development while there were still many characteristics about the device that needed to be worked out and tested. The problems that resulted would have been identified and fixed far more quickly using a low-cost benchtop test set-up with off-the-shelf components.  

  • A company attempted to go into production, using the first form-factor prototype design that was only intended to validate the performance of technical features. The company quickly learned the design could not be reliably built and had reliability issues in the field. Currently, the redesign costs are quite large as the engineers try to mitigate the technical challenges and still minimize impacts to the finalized product.


About the Author(s)

Michael Kahn

Director of Firmware/EE, Product Creation Studio

Michael Kahn, electrical engineer, currently manages a talented team of electrical and embedded firmware development engineers at Product Creation Studio. He brings more than 25 years of experience in design, project management, engineering management in product development of medical, industrial, and consumer devices.

Product Creation Studio has an on-site model shop and electrical design lab that allows fast build and iteration of early mock-ups and prototypes. Our teams of engineers and technicians are experienced in quickly producing prototypes and mock-ups at the correct level of fidelity to cost-effectively develop or apply new technologies, and validate or modify requirements, in the early portion of the design cycle. Later in the development cycle, Product Creation Studio’s seasoned engineering and leadership teams, which have supported countless new product introductions, can help support development strategy and engagements with manufacturing partners to support a seamless transition into production.

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