COLOUR-CHANGING PAINT
The BMW ix Flow featuring E Ink is the first car whose paint colour can be changed at the touch of a button.
Head of the project Stella Clarke said that “by changing the colour of the car, we’re bringing personalisation to unforeseen levels”. She added: “We also see a lot of benefits from a usability and sustainability viewpoint.”
The changing colour can make the EV more efficient by taking into account light and dark colours in relation to reflecting sunlight and the absorption of thermal energy.
BMW explained: “A white surface reflects a lot more sunlight than a black one. Heating the vehicle and passenger compartment as a result of strong sunlight and high temperatures can be reduced by changing the exterior to a light colour. In cooler weather, a dark outer skin will help the vehicle 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 air conditioning. This reduces the amount of energy the vehicle electrical system needs and, with it, the vehicle’s fuel or electricity consumption.”
This principle could also increase range, as the E Ink wrap uses no energy to keep the chosen colour, only during the changing process.
The colour change is made possible by a wrap tailored to the contours of the car. When stimulated by electrical signals, the electrophoretic technology within (similar to that used by Kindle e-readers) brings different pigments to the surface, causing the skin to take on the desired colour.
There are millions of paint capsules in the wrap, with a diameter equivalent to the thickness of a human hair. Each contains negatively charged white pigments and positively charged black pigments. Depending on the chosen setting, stimulation by an electrical field causes either the white or the black pigments to collect at the surface of the microcapsule, producing the desired shade.
Achieving this involves using many electronic paper segments, designed to reflect the contours of the car and variations in light and shadow.
Clarke said early indications show that repairing the E Ink wrap won’t be a huge issue: “It’s certainly repairable and not unrealistic from that aspect.”