Color that isn’t.

Ever wondered about reality and what you see, for example, the nacre of an abalone shell, a soap bubble containing a rainbow or a blue butterfly. What you see doesn’t actually exist. There are no “pigments” that give the Morpho butterfly its mesmerizing shimmer; instead, Morpho butterflies’ wings create the spectrum of blue and indigo by causing white sunlight waves to diffract and interfere. You witness the Universe at work.

Nature inspired the devices and experiences of today.

Many types of butterflies use light-interacting structures on their wing scales to produce color. The cuticle on these butterflies’ wings’ scales comprises nano- and microscale, transparent, chitin-and-air layered structures. Rather than absorb and reflect specific light wavelengths as pigments and dyes do, these multi-scale structures cause light that hits the wing’s surface to diffract and interfere.

California Academy of Sciences (Abi Brody)

Cross ribs that protrude from the sides of ridges on the wing scale diffract incoming light waves, causing the waves to spread as they travel through spaces between the structures. The diffracted light waves then interfere with each other so that certain color wavelengths cancel out (destructive interference) while others are intensified and reflected (constructive interference). The varying heights of the wing scale ridges appear to affect the interference such that the reflected colors are uniform when viewed from a wide range of angles. The specific color that’s reflected depends on the shape of the structures and the distance between them. This way of manipulating light results in brilliant iridescent colors, which butterflies rely upon for camouflage, thermoregulation, and signaling.

Why the talk about structural light? Many people and the media have talked about Huawei’s ‘Twilight‘ gradient color scheme of the P20 Pro Series released in 2018, a little bit after I left Huawei. Available exclusively to the Huawei P20 Pro, the shimmering finish has been discussed ever since the color was first announced. Featuring a gradient that smoothly transitions from purple to blue then to aqua works in the same order laws of physics sort colors on the visible light spectrum as described above. Using the Morpho butterfly example — underneath a premium glass back, the Twilight variant of P20 Pro. So what inspired this sublime color scheme? One needs only look out of the window and gaze at the sky for the answer.

Twilight P20 Pro Series

That‘s right; it was nature, the world’s greatest artist of all time, that inspired us. Designing both the hardware and software, we have been taking cues from nature and the best of the best design and art. For the Twilight color, we were inspired by the Tyndall effect and the Aurora Borealis, or better known as the Northern Lights.

Northern Lights Aurora Borealis

It does not take formal training for one to appreciate nature, for our ability to perceive nature as a thing of beauty is innate to all of us. Throughout history, nature has inspired countless great painters to create great masterpieces. In China, court painters through dynasties transposed their impressions of the natural landscape onto paper using ink, water, and a brush. Towering mountains, rolling hills, and narrow rivers were painted onto scrolls of paper with lively brushstrokes, dots, and ink wash. This ancient art form, known today as guohua, is considered one of the most respected in classical Chinese art. In the West, greats such as Claude Monet and Vincent van Gogh were also no strangers to nature. Monet rejected the stylistic norms of his time and developed his own way to capture nature's beauty, using his observations of changing lights to encapsulate the beauty he beheld. Just like some of the greatest artists throughout history, at Huawei, we were inspired by nature. We developed the dreamy color scheme to capture the magnificence and mysteriousness of the aurora. Careful decisions were made to ensure that when the gradient effect is shrunk to a handheld device's size, the phenomenal natural intensity will retain its full glory.

Good to know

Brilliant iridescent coloring in male Morpho butterflies enables long-range conspecific communication. It has long been accepted that microstructures, rather than pigments, are responsible for this coloration. Few studies, however, explicitly relate the intra-scale microstructures to overall butterfly visibility, both in terms of reflected and transmitted. We investigated the absolute reflectivity and transmissivity associated with the single-scale microstructures of two Morpho butterflies' species and the mechanisms behind their excellent wide-angle visibility with lasers. Measurements indicate that individual Morpho microstructures reflect up to 75% of the incident blue light over an angle range of greater than 100 degrees in one plane and 15 degrees in the other.

We show that incorporating the second layer of more transparent scales above a layer of highly iridescent scales leads to very strong diffraction, and we suggest this effect acts to increase the angle range over which incident light is reflected.

Measurements using index-matching techniques yield the complex refractive index of the cuticle material comprising the single-scale microstructure to be n=(1.56 plus or minus 0.01) + (0.06 plus or minus 0.01)i. This figure is required for the theoretical modeling of such microstructure systems. (Vukusic et al. 1999:1403)