Achieving the blackest of blacks has been one of humanity’s enduring challenges. It is a frontier that unites modern nanotechnologists with nature’s ancient colour palette.
Black emerged as one of humanity’s first engineered colours, stemming from charcoal and soot used in the prehistoric cave art of Lascaux in southwestern France.
For centuries, darkness has been associated with power, rarity and prestige. In Renaissance Europe, richly dyed black fabrics became symbols of wealth and authority, adorning monarchs, judges and aristocrats. Black conveyed status because producing a deep, uniform darkness was technically demanding and prohibitively expensive.
But the pursuit of ever-deeper black is more than just an aesthetic endeavour. At the turn of the 20th century, German theoretical physicist Max Planck sought to explain the mystery of blackbody radiation – and revealed fundamental laws governing the interaction of light and matter.
While Planck examined the theoretical behaviour of an ideal perfect absorber, today’s scientists have demonstrated materials that come astonishingly close to this in practice. Advances in nanotechnology – engineering at an atomic and molecular scale – have enabled the creation of ultra-black materials capable of absorbing virtually the entire spectrum of visible light. (The more light that is absorbed, the darker the black appears.)
One commercial example was BMW’s ultra-black concept car. Coated in “Vantablack”, a material composed of vertically aligned carbon nanotubes, the vehicle had an unreal appearance. Reflections vanished and contours collapsed into a seemingly two-dimensional silhouette.
Surrey NanoSystems via Wikimedia Commons, CC BY-NC
The artist Anish Kapoor’s exclusive licence to use Vantablack for artistic purposes proved controversial, with many artists arguing that such a privilege should not be reserved for a single practitioner. Kapoor’s striking void-like forms helped drive the development of alternative ultra-black materials which continues today.
Like absolute zero, perfect absorption is a theoretical limit we can progressively approach but never really reach. But with nature’s help, scientists are getting closer all the time.
Ultra black in nature
Long before engineers grew forests of carbon nanotubes, nature had already refined its capacity to create ultra-black structures.
In the perpetual darkness of the deep ocean, fish species evolved skin capable of absorbing nearly all incoming light, rendering them effectively invisible to predators. Their camouflage arises from delicate surface architectures that capture photons with remarkable efficiency.
Evolution has also used darkness for the opposite objective. In birds of paradise and some butterflies, ultra-black structures serve not for concealment but display. Set beside intensely iridescent colours, these ultra-dark spots absorb so much light that they create the illusion of voids. This makes neighbouring colours appear brighter, richer and more luminous.
Studies of birds of paradise have found light reflection values as low as 0.05-0.31% – approaching those of the latest engineered ultra-black metamaterials. The birds’ feathers contain highly modified barbules arranged in tilted arrays which force incoming light to scatter repeatedly, producing their velvety ultra-black appearance.
Natalia Golovina/Alamy
In all these cases, colour and darkness emerge from geometry, morphology (surface patterns such as ridges, grooves and pores) and topology (how these patterns are arranged).
Modern nanotechnology is embracing this biomimetic strategy. Ultra-black coatings based on vertically aligned carbon nanotube forests echo the solutions perfected by deep-sea organisms, butterflies and birds of paradise.
Billions of carbon nanotubes act as artificial optical traps, forming dense labyrinths into which light photons readily enter but cannot escape. The result is a synthetic material that rivals, and in some respects surpasses, the optical performance of nature’s darkest surfaces.
Modern ultra-black uses
Today’s ultra-black carbon nanotube materials are employed wherever unwanted reflections might compromise performance.
In astronomy, ultra-black coatings line the inside of telescopes to absorb stray light. Without them, the glare from nearby stars would mask the faint reflection from distant galaxies and exoplanets, leaving many of these worlds invisible.
In high-resolution microscopes and scientific cameras, ultra-black surfaces eliminate reflections that blur images, revealing details that would otherwise remain hidden. In spectroscopy and quantum sensing, they suppress background noise so that extremely weak signals from molecules and photons can be detected.
Ultra-black coatings also improve thermal management by absorbing and controlling heat, making them ideal in spacecraft, satellites and high-performance electronics where even minor temperature changes can affect performance. In solar thermal systems, they maximise sunlight absorption, increasing the efficiency of converting solar energy into heat.
Carbon nanotube coatings also help aircraft, drones and satellites lower both visible and infrared signatures, making them more difficult to detect by cameras, thermal imaging systems and radar. They could also reduce light pollution in our night sky.
Whereas earlier ultra-black systems were often fragile, achievable only through complex nanofabrication, a recent Chinese study shows how robust, strongly adhering ultra-black coatings can now be generated using far more practical, industry-compatible strategies.
As the study highlights, waterborne carbon nanotube composite materials exemplify this progress, achieving light absorption above 99.9% while maintaining the durability required for highly demanding applications in the automotive industry.
What began as a symbol of status has become a state-of-the art technological challenge. The darkest blacks are no longer defined by pigments but by carefully engineered structures that absorb, trap and silence photons with extraordinary efficiency.
