In the 1960s, James Bond’s Aston Martin had changing numberplates and in 2021, BMW’s iX Flow featuring E Ink has changing body colours. But just like the feature on James Bond’s car, don’t expect it to be offered on BMWs anytime soon. It is a demonstration of future technology for a model displayed this week at CES 2022 (the consumer electronics trade show in Las Vegas) to show how digitisation can be used to adapt the exterior of a vehicle to different situations and individual wishes.

The fluid colour changes are made possible by a specially developed body wrap that is tailored precisely to the contours of the all-electric Sports Activity Vehicle from BMW. When stimulated by electrical signals, the electrophoretic technology brings different colour pigments to the surface, causing the body skin to take on the desired colouration.

More sophisticated personalisation
The use of innovative E Ink technology opens completely new ways of changing the vehicle’s appearance in line with the driver’s aesthetic preferences, the environmental conditions or even functional requirements. The technology thus offers unprecedented potential for personalisation in the area of exterior design and the iX Flow demonstrates this potential to impressive effect.

Already today, the colour chosen for a car is an expression of the driver’s personality. The choice of exterior finishes available for current BMW models covers a wide colour spectrum. In this way, the longing for a wildly expressive, extravagant, or sporty appearance on the outside can be taken into account as well as the desire for an understated, subtle or elegant appearance.

Against this background, the BMW Group is driving the development of the technology so that a new form of personalisation can be experienced both on the outside and in the inside of future production vehicles. Apart from a greater degree of personalisation, a customer will also not have to settle for just one colour – he or she can have many more for different occasions!

“This gives the driver the freedom to express different facets of their personality or even their enjoyment of change outwardly, and to redefine this each time they sit into their car,” said Stella Clarke, Head of Project for the BMW iX Flow featuring E Ink. “Similar to fashion or the status ads on social media channels, the vehicle then becomes an expression of different moods and circumstances in daily life.”

Increased efficiency too
A variable exterior colour can also contribute to wellness in the interior and to the efficiency of the vehicle. This is done by taking account of the different abilities of light and dark colours when it comes to reflecting sunlight and the associated absorption of thermal energy. A white surface reflects a lot more sunlight than a black one. By implication, heating of the vehicle and passenger compartment as a result of strong sunlight and high outside temperatures can be reduced by changing the exterior to a light colour. In cooler weather, a dark outer skin will help the vehicle to absorb noticeably more warmth from the sun.

In both cases, selective colour changes can help to cut the amount of cooling and heating required from the vehicle’s air conditioning. This reduces the amount of energy the vehicle electrical system needs and with it also the vehicle’s fuel or electricity consumption. In an all-electric car, changing the colour in line with the weather can therefore also help to increase the range. In the interior, the technology could, for example, prevent the dashboard from heating up too much.

E Ink technology itself is extremely energy efficient (though, at this time, it would be very expensive technology). Unlike displays or projectors, the electrophoretic technology needs absolutely no energy to keep the chosen colour state constant. Current only flows during the short colour changing phase.

Millions of paint capsules
Electrophoretic colouring is based on a technology developed by E Ink that is most well-known from the displays used in eReaders like Kindle. The surface coating of the iX Flow contains many millions of microcapsules, with a diameter equivalent to the thickness of a human hair. Each of these microcapsules contains negatively charged white pigments and positively charged black pigments. Depending on the chosen setting, stimulation by means of an electrical field causes either the white or the black pigments to collect at the surface of the microcapsule, giving the car body the desired shade.

Achieving this effect on a vehicle body involves the application of many precisely fitted ePaper segments. Generative design processes are implemented to ensure the segments reflect the characteristic contours of the vehicle and the resulting variations in light and shadow. The generative design algorithms enable the necessary formability and flexibility required to tailor the ePaper exactly to the design lines of the vehicle.

Laser cutting technologies are used to guarantee high precision in generating each segment. After the segments are applied and the power supply for stimulating the electrical field is connected, the entire body is warmed and sealed to guarantee optimum and uniform colour reproduction during every colour change.

“Digital experiences won’t just be limited to displays [inside the car] in the future. There will be more and more melding of the real and virtual. With the BMW iX Flow, we are bringing the car body to life,” said Frank Weber, Member of the Board of Management of BMW AG, Development.