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Smart Textiles

No longer “any colour as long as it’s black”…

Electrophoretic technology brings different colour pigments to the surface skin of a vehicle.

6th January 2022

Innovation in Textiles
 |  Las Vegas

Transport/​Aerospace

BMW is showcasing an extraordinary new technology at CES 2022 – the world’s largest electronics show taking place in Las Vegas from January 5-8 – a specially developed digitally-activated body wrap for vehicles that enables the driver to adapt the exterior shades of a vehicle to different situations.

The surface of the new BMW iX Flow featuring E Ink can vary its shade at the driver’s prompting. The fluid colour changes are made possible by a specially-developed surface that is tailored precisely to the contours of the all-electric sports activity vehicle. 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.

Electrophoretic colouring is based on a technology developed by E Ink that is most well-known from the displays used in eReaders. The surface coating of the BMW iX Flow featuring E Ink 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.

Electrophoretic technology brings different colour pigments to the surface, causing the body skin to take on the desired colouration.

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 design algorithms enable the necessary formability and flexibility required to tailor the ePaper exactly to the design lines of the vehicle.

Laser cutting technologies 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 in the future,” said Frank Weber, a member of BMW AG’s board. “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.”

A variable exterior colour can contribute to wellness in the interior and to the efficiency of the vehicle, BMW says, 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 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 is also extremely energy efficient. Unlike displays or projectors, the electrophoretic technology needs absolutely no energy to keep the chosen colour state constant and current only flows during the short colour changing phase.

www.bmw.com

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