The role of color in medical devices: a designer’s perspective

How does look and feel play a part?

We cannot assume that look, feel, and interface design of a product alone will help tackle compliance and adherence issues. Adherence is an extremely complex subject where many factors need to be considered. Those include education, the quality of training and support material, how the benefits of a therapy are communicated and of course, cost.

However, by carefully considering the practical, emotional and lifestyle challenges faced by the users of our products, we can design an experience that at least helps to reduce the barriers to compliant use – and choosing the right colors can play a key role in helping to achieve this.

Practical issues

The considered use of color can help us to overcome numerous practical design challenges. Color can emphasize key interaction points on a user interface (such as an actuation button or a dose selector), and by using a hierarchy of colors, we can influence the user’s interaction, helping them to follow the correct usage steps in the correct order. Color can also be used to aid with instructions – by color coding different components it can make it easier to provide written or graphical instructional information. For example, the EpiPen uses color-coded features referred to in the on-board instructions such as ‘pull off blue safety release’ and ‘push orange tip against outer thigh’.

Regulators are encouraging the use of color in packaging and labeling.

Regulators are encouraging the use of color in packaging and labeling to help users identify between different types, strengths and dosages of drugs. The FDA produced simple guidelines (Recommendations for Developing User Instruction Manuals for Medical Devices Used in Home Health Care, FDA) which encourages using color to help identify key information. The color used can be more sophisticated and we can use it to tie different elements of a system together. For example, if someone had two capsule inhalers from two different brands, it might be easy for them to get confused over which capsule goes in which device. If, however, there was an overriding color scheme in the device, drug packaging and instructions, this could provide a clear and easy to understand visual aid that would improve usability and compliance.

Emotional issues

Color can also be used to trigger emotional responses. Think about how the packaging of your favorite brand of chocolate can trigger the sensation of taste and smell long before you’ve opened the wrapper. Our perception of the size and weight of a product can be altered depending on its color. Darker colors can make something feel heavier and more robust, while a semi-translucent color feels lighter.

Color can also affect the value we place on a product. Some colors encourage a disposable attitude after a device is used one time because “it feels low cost and throw-away”. Other colors instill a feeling of cleanliness, such as pure whites, aqua blues, or fresh greens. Think about the colors typically used on your toothbrushes – it might feel odd to put them in your mouth if they were khaki. Certain colors can also indicate whether a tool is made for professionals, novices or even children.

Carefully chosen shades and hues or metallics can create particular ideas or perceptions, it is important for medical devices to appear of an appropriate value and quality to gain confidence and trust from users. It is therefore extremely important to get the color just right – but in the design of medical products life isn’t quite so simple, as we don’t have the freedom of choice from standard color palettes that we would if designing consumer products. For example, we may have a single shade of yellow to choose from in a standard medical range, while we’d have 15 shades of yellow in a range of colors suitable for consumer product use – marigold, jasmine, canary, sunflower, sherbet lemon and so on.

Getting the right shade is important

Having a standard color palette is helpful as a starting point: if we select a color from a pre-approved medical range then we greatly reduce the amount of test work required to prove the color is safe and achievable. However, due to the limited choice on standard color palettes more often than not it is likely that a custom color will need to be processed – and this isn’t always entirely straightforward. However, this is not an issue if planned ahead.

An example is the surgical hemostat spray developed for ProFibrix. Aesthetically, the device needed to feel disposable as it is a single-use device, clinical with a hygienic feel, professional as it is used by surgeons, but practical so it was not too complicated to use. We chose to use color to clearly identify key interaction points and settled on a clean, minimal color palette of just three colors – white, blue and grey. However, the device also had several specific material requirements. It needed to be gamma stable for post-sterilization, a flexible material was needed for a compliant vial seal and low friction for its nozzle attachment and a strong durable material for the handle.

The white of the body was straightforward – we used a precompounded white ABS which we’d used successfully many times before on other devices. The grey available from the standard Mevopur range met our needs, but our key accent color needed something custom.

Initially, a teal color was chosen to highlight the key interaction points of the device and to complement our client’s core brand colors. However, not all colors are physically achievable in the world of medical device design. The color we specified required three different pigments: a blue, a white and a green. While all pigments were pre-approved for medical use the green pigment had a low processing temperature compared to the blue and white and the material to be colored had a high processing temperature.

Not all colors are physically achievable in the world of medical device design.

Because there was such a small amount of the green pigment, it was burning out during the compounding process, making it difficult to achieve a robust manufacturing process. Following discussions with our supplier (in this instance Clariant), we were presented with further options – a darker teal or a more similar shade of blue. As medical device designers, a practical approach is necessary when presented with decisions like this. While we need to find a color that helps to communicate the right message, we also need to de-risk the manufacturing process. Working together with Clariant we were able to develop a blue color that has the same vibrancy and clinical connotations, but by reducing the number of pigments used we also reduced the risk of any unforeseen interaction with other materials. Again, getting the right shade is not an issue if the process is planned well in advance.

Color and regulations

Choosing a color is also dependent on regulations. Many color manufacturers are leading the way with regulatory compliance. When choosing a color, you have to bear in mind the regulations and impact on mechanical properties. By choosing the wrong pigment, you could influence the device reliability and thus administrate the wrong dose. Another issue to consider while choosing colors is that the raw materials could change leachable profiles and invalidate testing done in development. This is true even when choosing a pre-approved color. Final leachable and extractable testing must always be undertaken with the final combination of masterbatch and polymer.

Consideration must be given to the raw materials supply chain as changes may occur over the device life cycle (see FDA potential for leachables and extractables scheme) and thus could change leachable profiles and invalidate testing done in development (see pyramid).

The FDA has started to understand the risks of change in materials in the product lifecycle. This is why it is important to design ‘risk management’ into the manufacturing process, looking beyond the 1st upstream supplier and discussing what is possible: having a Change Control agreement with the color supplier and using pre-tested raw materials so it can be understood where risks may stem from. This will not only help to reduce potential risk but will create opportunities to improve the process as well as the product.

Conclusion

Color plays an important part in the design of medical devices – through carefully considered color schemes, it can help us tackle both practical and emotional design challenges. Helping to build trust and confidence with both patients and healthcare professionals in the devices we develop.

Where possible the use of pre-approved color and material combinations will help to reduce risk during the manufacturing process. But as long as you build time into your plan and engage early input from a duly experienced colorant manufacturer, you will increase your options and should have a full spectrum of choice.