Plastics are among the most versatile and indispensable materials in modern medical device development.

From syringes and catheters to surgical instruments and implantable components, plastics enable engineers to translate clinical concepts into safe, effective, and reliable products. Their unique combination of properties (moldability, strength-to-weight ratio, biocompatibility, transparency, and sterilization resistance) makes them central not just to manufacturing efficiency, but to fulfilling the very purpose of medical devices.

However, turning high-level product requirements into specific, testable plastic requirements is not always straightforward. For plastics in particular, the stakes are high: design changes made late in the development process can be extremely costly, such as having to commission a new injection mold or having to re-commission biocompatibility or sterility tests. At the same time, we always want to keep an eye on the spectre of overengineering. Specifying materials with unnecessary properties or tolerances that drive up costs without improving clinical outcomes.

Beyond cost, the way plastics are selected and applied has a significant impact on a device’s sustainability profile. Serving today's climate conscious markets, we need to pay attention to the fact that plastics being a major contributor to the CO₂ footprint of medical devices, every decision, from material choice to part design, influences not only performance and safety, but also whether the device supports long-term environmental goals.

Not all product requirements can be directly translated into plastic properties. Although some neatly map onto known plastic characteristics, such as tensile strength or impact resistance, others are more qualitative in nature and consequently require analysis and interpretation.

Product requirements that relate to plastics describing how a device should perform in use or how it should feel to the user, for example, “a transparent housing for monitoring”, or “a soft grip for comfort” must be carefully transformed into measurable, verifiable material specifications that can actually guide design and testing.

Every requirement that flows down into material specifications carries consequences for cost, usability, regulatory compliance, and sustainability. If left unexamined, requirements risk becoming bloated with “nice-to-haves” that add little or no value to patients or clinicians. This kind of over-specification is particularly problematic in plastics, where excessive safety margins can easily translate into thicker parts, more complex materials, or additional processing steps, all of which drive up costs and carbon footprint.

Asking the right questions early prevents this. Instead of simply asking “Why is this required?”, which can lead to defensive justifications, it is more effective to ask “How do we know this is required?”.

That shift reframes the discussion around evidence and traceability — whether the requirement is grounded in a regulatory clause, a user need, a clinical claim, or solid engineering data. By questioning requirements in this way, teams can separate what is truly necessary from what is merely assumed.

This process not only reduces the risk of overengineering but also ensures that every plastic requirement serves a clear purpose: to support the clinical claim, safeguard the patient, or meet a regulatory expectation. Anything beyond that is cost, complexity, and CO₂ emissions without benefit.

How do we best formulate a plastic requirement given a product requirement? This takes us to the core of this discussion. Based on my extensive expertise and long experience in this domain, I have learnt that a key principle in deriving plastic requirements is: the verification method drives the formulation of the requirement.

When drafting a plastic requirement, always consider: How will this be verified?

Let’s walk through an example:

Step 1: Inspect the Product Requirement

Let’s say the product requirement states: “The handle has to be soft.”

Step 2: Consider Verification Options

There are several approaches to how softness can be verified:

User Evaluation with Material Samples

Provide different material samples to representative users and ask them to choose the one that best matches their expectation of “soft.”

Prototype Testing

Build early prototypes and let users handle them to assess perceived softness.

Defined Parameter Measurement

Translate softness into a measurable property, such as Shore hardness, and test against a specified range.

Step 3: Assess Verification Methods

Not all verification methods are created equal. Each verification option differs in cost, time, and effectiveness. Therefore, apply a system where you grade the verification methods according to these three parameters: cost, time and effectiveness. Score the different verification methods and select the verification methods with the best score.

Step 4: Select and Formulate the Requirement

Once you have established your verification method of choice, go ahead and formulate the plastic requirement accordingly. If Shore hardness proves to be the most reliable and cost-effective method, the requirement should be stated as:
“The handle material must have a Shore A hardness between 30 and 40.”

This statement is clear, measurable, and directly verifiable.

Best Practices for Writing Plastic Requirements

Challenge Rationales – Especially when requirements are claimed to be “regulatory.” Always ask for the exact clause or reference.

Avoid Overengineering – Resist specifying “the best” when “good enough” meets user needs, patient safety and clinical effectiveness. Remember that every added property has the potential to increases cost and environmental impact.

Tie Every Requirement to Verification – If you can’t verify it, you can’t require it.

Closing Thoughts

Plastics are unique and versatile, but they require thoughtful specification. By working backward from how a requirement will be verified, medical device engineers can ensure that plastic requirements are both practical and defensible. The result: safer devices, leaner development, and more sustainable products.

Lucas Pianegonda, founder of Gradical, is a globally recognized expert in sustainable plastics for medical technology. He supports MedTech companies in choosing the right plastic for their applications, combining deep technical expertise with a strong focus on sustainability.

Recently elected to the board of the European Medical Division of the Society of Plastics Engineers he will bring in his expertise to push the boundaries of sustainability in MedTech. Lucas also hosts the “Plastics in Medical Technology” podcast, where he explores plastics, MedTech innovation and sustainability.