Black Paint That Makes Objects Easier for Autonomous Vehicles to Detect
Driving at night can be a daunting challenge for a new driver, but with hours of practice it soon becomes second nature. For autonomous vehicles, however, practice alone may not be enough, since the lidar sensors that often serve as their "eyes" struggle to detect dark-colored objects. A study published in the journal ACS Applied Materials & Interfaces describes a highly reflective black paint that could help these vehicles detect dark-colored objects, making autonomous driving safer.
Driving a vehicle at night may be a daunting challenge for a new driver, but with hours of practice it quickly becomes second nature. For autonomous vehicles, however, practice may not be sufficient; because lidar sensors, which frequently serve as the "eyes" of these vehicles, struggle to detect dark-colored objects. A study published in the ACS Applied Materials & Interfaces journal describes a highly reflective black paint that could help these vehicles see dark-colored objects and make autonomous driving safer.
Lidar is short for "light detection and ranging" and is a system used in many applications from geological mapping to autonomous vehicles. The system works similarly to echolocation; however, instead of sound waves, it emits very short pulses of near-infrared light. These light pulses bounce off objects and return to the sensor, allowing the system to create a three-dimensional map of its surroundings. However, lidar falls short when objects absorb more near-infrared light than they reflect, as is the case with black painted surfaces.
Because lidar cannot detect these dark-colored objects on its own, one common solution is for the system to rely on other sensors or software to fill in information gaps. However, this approach can also lead to accidents in some cases. For this reason, Chang-Min Yoon and colleagues aimed to make dark-colored objects easier to detect with existing technology by developing a specially formulated, highly reflective black paint rather than reinventing lidar sensors.
To produce the new paint, the team first created a thin layer of titanium dioxide (TiO₂) on small glass particles. The glass was then etched with hydrofluoric acid, leaving behind a porous, white, and highly reflective TiO₂ layer. This structure was then reduced with sodium borohydride to convert it into a black material that retained reflective properties. When this material was mixed with varnish, it became applicable as a paint.
The team then tested the new paint with two different types of commercially available lidar sensors: a mirror-based sensor and a 360-degree rotating sensor. For comparison, a conventional carbon black-based paint was also evaluated. Both sensors easily detected the specially formulated, TiO₂-based paint, while they could not detect the conventional paint in the same way.
Researchers note that this highly reflective material could enhance road safety by making dark-colored objects more visible to autonomous vehicles equipped with current lidar technology.
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