Paint it black(er): A new way to make cars darker than ever

Scientists have developed a practical way to make ultra-black coatings fit to meet the demand for trendy, luxury vehicles in China. The coating, described in a paper publishing June 18 in the Cell Press journal Matter & Light, is made up of a composite of carbon black pigment and carbon nanotubes. The resulting color is a deep jet black that also meets automotive standards, opening the door for car manufacturers to develop distinguished, high-end models in darker-than-ever hues. 

“In China, car color has become a key selling point,” says author Zhiwei Liu, a research chemist with the Color Technology, Group Core R&D Shanghai, Nipsea Group. “Deep black finishes have long been the premium choice and signature color for luxury cars due to their elegant appearance, powerful visual impact, and luxurious undertone. As a result, automotive coating companies have been actively pursuing innovations in color technology to develop mass-processable ultra-black coating solutions with extreme blackness.” 

In 2019, a BMW concept car with a vertically aligned carbon nanotube (VACNT) array coating set off a race in the automotive industry to develop coatings that similarly absorb almost all light, creating a “black hole” effect that gives vehicles a pronounced, dark appearance. The industry has been on the hunt for more practical ways to achieve this ultra-black effect with automotive coating-grade properties.  

Liu’s team developed a stable, nano-sized carbon black pigment-carbon nanotube composite, which they incorporated into a coating binder and sprayed onto a car model as an automotive coating. 

While current approaches to making black coatings rely on carbon black dispersions alone to absorb intrinsic light, imposing a limit on how black the coating can be, the team’s new approach uses “structural absorption,” pushing the material’s light absorption efficiency to new levels and enabling it to absorb an average of 99.90% of visible light wavelengths. The film also showed excellent long-term stability even when the researchers exposed it to water and humidity tests, pointing to its value for industrial applications.  

“With the rapid development of dispersing technology and equipment, there is still room for improvements in practical processability of carbon-nanotube-containing nanomaterials,” says Liu. 

Making the coating with a higher proportion of carbon nanotubes can further increase its capacity to absorb light, he added, although this would also bring difficulties in industrial-grade processability. In the future, he said, the researchers may also develop an ultra-black coating that contains multiple layers, with a gradient refractive index that reduces interface reflection and further enhances light absorption efficiency for an even darker look. 

While the researchers have completed the technical proof-of-concept design for the coating’s manufacturing process, it may still be a while before ultra-black cars made with this film will be able to hit the road.   

“Further efforts will focus on the verification of coating application window and the comprehensive film performance validations of carbon black pigment-carbon nanotubule composite-based ultra-black automotive coating,” says Liu. 

### 

This work was supported by Color Technology, Group Core R&D (Shanghai), NIPSEA Group. 

Matter & Light, Liu et al., “Robust ultra-black automotive coating with structural absorption and high absorption efficiency based on waterborne carbon black/CNT composite” https://www.cell.com/matter-light/fulltext/S3117-5848(26)00015-3

Matter & Light, published by Cell Press, is a journal publishing review articles and research that enhance the understanding of the intricate interactions between light and materials across various scales. The journal aims to advance theoretical understanding of light-matter interactions and push the boundaries of practical applications and technological solutions. To learn more, visit https://www.cell.com/matter-light/home. To receive Cell Press media alerts, please contact press@cell.com.