The role of colour 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 which at least helps to reduce the barriers to compliant use – and choosing the right colours can play a key role in helping to achieve this.

Practical issues

The considered use of colour can help us to overcome numerous practical design challenges. Colour can emphasise key interaction points on a user interface (such as an actuation button, or a dose selector), and by using a hierarchy of colours we can influence the user’s interaction, helping them to follow the correct usage steps in the correct order. Colour can also be used to aid with instructions – by colour coding different components it can make it easier to provide written or graphical instructional information. For example, the EpiPen uses colour-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 colour in packaging and labelling

Regulators are encouraging the use of colour in packaging and labelling to help users identify between different types, strengths and dosages of drug. The FDA produced simple guidelines (Recommendations for Developing User Instruction Manuals for Medical Devices Used in Home Health Care, FDA) which encourages using colour to help identify key information. The colour 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 colour scheme in the device, drug packaging and instructions, this could provide a clear and easy to understand visual aid which would improve usability and compliance.

Emotional issues

Colour can also be used to trigger emotional responses. Think about how the packaging of your favourite 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 colour. Darker colours can make something feel heavier and more robust whilst a semi-translucent colour feels lighter.

Colour can also affect the value we place on a product. Some colours encourage a disposable attitude after a device is used one time because “it feels low cost and throw-away”. Other colours instill a feeling of cleanliness, such as pure whites, aqua blues or fresh greens. Think about the colours typically used on your toothbrushes – it might feel odd to put them in your mouth if they were khaki. Certain colours 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 colour 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 colour 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 whilst we’d have 15 shades of yellow in a range of colours suitable for consumer product use – marigold , jasmine, canary, sunflower, sherbet lemon, and so on.

Getting the right shade is important

Having a standard colour palette is helpful as a starting point: if we select a colour from a pre-approved medical range then we greatly reduce the amount of test work required to prove the colour is safe and achievable. However due to the limited choice on standard colour palettes more often than not it is likely that a custom colour 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 haemostat 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 colour to clearly identify key interaction points; and settled on a clean, minimal colour palette of just three colours – white, blue and grey. However, the device also had several specific material requirements. It needed to be gamma stable for post-sterilisation, 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 colour needed something custom.

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

not all colours 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 colour 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 colour 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.

Colour and regulations

Choosing a colour is also dependent on regulations. Many colour manufacturers are leading the way with regulatory compliance. When choosing a colour, 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 colours is that the raw materials could change leachable profiles and invalidate testing done in development. This is true even when choosing a preapproved colour. 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 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 colour 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

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

Where possible the use of preapproved colour 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 colourant manufacturer, you will increase your options and should have a full spectrum of choice.