YSM Issue 94.3

FOCUS
Ornithology
IMAGE COURTESY OF VINODKUMAR SARANATHAN
Dr. Vinodkumar Saranathan with models of a double gyroid (left) and single gyroid (right).
these components, backfill the empty
space with gold, and burn away the
remaining organic complement. This
process leaves a single gyroid made
of gold, which can then be used as a
template to form single gyroids from
other materials.
Inherent limits in this double gyroid
etching process make it impossible to
synthesize single gyroids larger than fifty
nanometers in unit size. Unfortunately,
single gyroids that interact effectively
with light are around five-hundred
nanometers. Researchers have yet to
find a way to synthesize one of that size.
Both butterflies and birds, however, have
figured out the process.
Making Single Gyroids
Saranathan used X-ray analysis to observe
the β-keratin structures in other species
that are sister species to single gyroid
leafbirds. He found swathes of keratin
nano-spaghetti, assembled through
phase separation. Prum noted that it is
highly likely that two species diverged
from a common ancestor by way of the
nanostructure formed, keeping the same
general formation process.
Crystal structures produce more
saturated colors. For that reason,
Saranathan suggested that keratin
structures resembling single gyroids were
preferred by some female leafbirds over
those resembling nano-spaghetti.
Nevertheless, these birds somehow form
single gyroid crystals without ostensibly
having to form a double gyroid first.
“The way they are making this is new to
science, period,” Saranathan said. “New
to biology, new to engineering, new to
physics.” Birds’ spontaneous self-assembly
of these structures illuminates the exciting
potential for humans to recreate this selfassembly
in the laboratory.
Single gyroids and their discovery in
living systems represent a breakthrough
in a vast number of scientific disciplines.
The optical structures used by birds to
make colors can also be used to better
manipulate the flow of light. This makes
them highly applicable in solar cell
technology. A structural approach to
creating color, rather than one based off
pigments, could inspire the development
of sustainable and less toxic paints,
tiles, textiles, and cosmetics that resist
fading over time, too. Furthermore, the
formation of networks and gel matrices
from large liquid-like particles, similar
to how keratin forms single gyroids,
is a process nearly ubiquitous in cell
biology. A better understanding of single
gyroid synthesis could lend insight into
organelle-less phase separation—a
widely growing area of interest in cell
biology—soft-condensed matter physics,
and physiological systems.
In an age where nanotechnological
structures in computer chips and rapiddiagnostic
tools are designed to optimally
control the flow of electrons and light,
learning from self-assembled structures
like single gyroids could open up whole
new areas of research. “This is an example
of why I think bird-watching science
matters,” Prum said. “That tension
between irregularity and specificity is
something that I really enjoy, and this
research is a great example of the way in
which that works together.” ■
Curiously, butterflies make single
gyroids the same way researchers do—
only somehow, they’re able to make them
ten-times larger than engineers can.
But “the birds,” Saranthan said, “are
completely revolutionary.” In contrast
to butterflies, there’s no templating.
Birds like the blue jay seem to make
single gyroids spontaneously by phase
separation, as if they dropped a quarter
in a glass of soda and single gyroids
assembled on the coin’s surface.
To ascertain the spontaneous generation
of single gyroids by phase separation,
24 Yale Scientific Magazine October 2021
ABOUT THE AUTHOR
RYAN BOSE-ROY
RYAN BOSE-ROY is a sophomore in Trumbull majoring in Biomedical Engineering and “something else,
we’ll figure out what it is.” In addition to writing for YSM, Ryan works the Trumbull buttery shift on
Sunday nights, where he delights in making quesadillas and regaling customers with stand-up bits while
taking their orders.
THE AUTHOR WOULD LIKE TO THANK Dr. Prum and Dr. Saranathan for their time and willingness to
be interviewed for the article. At the request of Dr. Saranathan (and at the author’s own discretion), the
author would like to acknowledge the Yale Peabody Museum for its existence.
FURTHER READING
​Saranathan, V., Narayanan, S., Sandy, A., Dufresne, E. R., & Prum, R. O. (2021). Evolution of single gyroid
photonic crystals in Bird Feathers. Proceedings of the National Academy of Sciences, 118(23). https://doi.
org/10.1073/pnas.2101357118
www.yalescientific.org