Learning from Nature: Advanced Biomimetic Materials | Panče Naumov || Radcliffe Institute


– Thank you, Meredith. I have been waiting
for this introduction, and it was simply amazing. Thank you very much. In a recent survey, I was
asked to describe Radcliffe in five words, and this might
look like an easy question to answer, but I soon realized
it was quite challenging, because there are so many
words that come to mind– encouragement, support,
diversity, inclusion, recognition, inspiration,
motivation, uplift, elevation. Many of these
universal values align with a history that
happened between these walls and are reflected in the
mission of the institute. Radcliffe is intellectually
rigorous, urban in location, bold in spirit, and
global in outlook. Radcliffe is about big and
important issues and ideas, like peace and governance,
health and equity, resources and tolerance. Radcliffe transforms,
enlightens, and empowers. I would like to
highlight that working in this academic
constellation has been an immensely intellectually
uplifting, professionally rewarding, and personally
transforming experience. To be an Radcliffe fellow
is both a great honor and a privilege, and I
can’t express how grateful I am to the leadership for
giving me this opportunity to be part of this. I would also like to
take this opportunity and highly recommend to
my fellow researchers from natural sciences to
apply for this fellowship, and to advance professionally
in a supportive stimulating and very dynamic setting. As Meredith mentioned, I
come with a cross-cultural experience, and throughout my
two decades of academic career, I learned to appreciate both
the benefits and challenges of culturally and socially
very diverse academic settings. I was born and raised in
Macedonia, a beautiful country with a very rich and long
history in southeastern Europe, but also a place which appears
to be constantly in transition. I spent half of my
professional career in Japan, an academic
environment which is in many ways
established and advanced, but which is also
generally viewed as rather rigid and conservative. I now work for New
York University in their portal campus
located in the Emirates, where one of the best private
American universities has set as its
mission to partake in the process of transforming
an authoritarian society within a very short
period of time. I also happen to
be the only chemist in this batch of
fellows, and when I was thinking about the subject
of this talk, the chemist in me was tempted to show you
something like this. I can lend you a few
slides of this sort if you ever suffer from
insomnia to help you with sleep. But in an attempt to
avoid being technical, instead I wanted to
take you on a journey and tell you about something
all of us can relate to, something that also
continues to inspire great scientific discoveries. I asked myself, what is it that
these so different cultures that I have experienced
have in common? In a recent interview for one
of the scientific journals, I stated that there
are two things that inspired me to become
a scientist– first, the curiosity. And second, the nature. I recognized very early in
life the full worth and beauty of nature. Instead my very
first recollections of my early childhood are those
of the beautiful green hills of Macedonia, where I was both
curious and inspired about how plants and animals
live and survive. I later discovered
that endorsing cognitive
connectedness to nature and engaging with
natural beauty is not only common for many
cultures, regardless of their social and
political milieu, but at an individual
level, it is also thought to be associated
with greater well-being and awareness for
environmental conservation. And that idea is perhaps
best sublime in this quote of John F. Kennedy
that you can find on a board in the
Kennedy memorial park right here in front of Harvard. But nature also has a quirky,
unexpected, or just downright weird side. Geckos can climb up walls
and stick to ceilings. Insects can walk on water,
and some snakes can even fly. These obscure corners
of the living world might sound like an episode
of Ripley’s Believe It or Not! Yet they happen more often
than we think about them, and more importantly, they
may hold enormous benefits to the humanity. Over the course of
millennia, plants and animals have developed and
perfected mechanisms for motion, survival, and
dispersal with astounding grace, speed, and versatility. But how do they do it, and
what can we learn from them? So in this next slide, you will
see the amazing efficiency, durability, adaptability,
and self-healing capability for which the biological
systems are in doubt. And these are some of
the main inspirations of the material scientist
as structure functionality principles. And if we look back in
time, the living beings had a very, very long
time to perfect themselves in order to survive. The age of the Earth is
about 4.5 billion years, and the earliest undisputed
evidence of life of art dates from at least
3.5 billion years ago, although there is also evidence
that life began much earlier. The global changes
with processes such as plate tectonics
and solar variability have occurred over thousands
to millions of years. On a much smaller scale,
over decades to centuries, the human activities have
become an important driver of the physical climate system
and the biochemical cycles. To just give you a feel of
how long it took the living organisms to evolve to what they
are now, insects such as ants have been around since
140 million years ago, while the squid have
been on this planet since about 100 millions ago. Our human lineage started only
about two million years ago, and about 200,000 years ago
our species, the homo sapiens, emerged. So you might want
to consider this the next time you
step on an ant or have your calamari for dinner. If aliens ever
visited our planet and they decided to
communicate with humans, one of their first
questions would probably be, how many distinct lifeforms
does your planet have? You would be surprised
with the uncertainty in our answer, which
illustrates our limited progress with this research topic. In more than 250 years
since the Swedish biologist Carl Linnaeus began the
science of taxonomy, 1.2 million species had been
identified and classified. It is estimated that it
will take us another 480 years to complete the job. However, the Linnaeus system
forms a pyramid-like hierarchy, which is inverted image of
the taxonomic rank shown here. The lower the category, the
more entities it contains. There are more
species than genera, more genera than families,
more families than orders, and so on right up to the top
levels, the kingdom and domain. Recently, a new
method was proposed that allows the total
number of species to be predicted based on
the consistent scaling pattern among the
different levels of taxonomic classification–
system, order, genus, species, and so on. According to the latest
biodiversity estimate based on this new
method of prediction, there are 8.7 million– give or take 1.3 million– eukaryotic species
on our planet. This means that a staggering
86% of land species and nearly 91% of marine
species remain undiscovered. With these numbers at hand,
we cannot even begin to answer questions such as how much
diversity we can lose while still maintaining these
ecosystem services that humanity depends on. So why are the
materials so important? Because about everything
you see around you is made of materials,
from the concrete walls to the intricate parts
of your smartphones, from the smallest grain of
sand to most complex systems like the living organisms. And we want these materials
to be lighter, thinner, smarter, better. We care about how they look
and feel, how long they last, and how much we need
to pay to use them. With great enthusiasm
and curiosity, material scientists
and engineers working in the biometric
materials research field ask why natural
selection may have favored one species over another
or one design over another. From the labs of
Harvard, here, and MIT to the deserts of
rain forests, they seek to answer why animals and
plants have adapted and evolved to disperse and traverse their
environments, taking advantage of physical laws and
environmental conditions with results that are both
startling and ingenious. Our desire and ability
to imitate nature has also continuously evolved,
and as technology improves, more difficult challenges
are yet to come. The humanity changed forever
during the first Industrial Revolution, which
began in Britain in the late 18th
century with the design of an engine in which
burning coal produced steam which drove a piston. The second Industrial Revolution
came in the early 20th century, when Henry Ford mastered
the moving assembly line and ushered in the age
of mass production. It witnessed the expansion
of electricity, petroleum, and steel. The first two
Industrial Revolutions made people richer
and more urban. Now a third revolution
is underway way. Manufacturing is going
digital, and a number of remarkable technologies
are converging. Clever softward and
more dexterous robots, new processes, a range
of web based services, and particularly important for
all these developments– novel and better materials. Living in the area of
emerging hyperconnectivity, we are on the cusp of the
fourth Industrial Revolution, or Industry 4.0. It is quite different than the
three industrial revolutions that preceded it,
because it is supposed to challenge even
our ideas about what it means to be human. The fourth Industrial Revolution
describes exponential changes to the way we live, work,
and relate to one another due to adoption of cyber
physical systems, the internet of things, and
the internet of systems. Implementation of smart
technologies in our factories and workplaces,
connecting machines that will interact
with each other, visualize the entire
production chain, and make decisions
autonomously– this revolution will impact all disciplines,
industries, and economies. And again, it requires
new, better materials. In parallel with
these developments, there have been
efforts to develop a global understanding of
the functioning of the earth as a system. The effort necessitated
linking knowledge, and unifying methodologies, and
conceptual frameworks from both the physical and biological
research domains, and will inevitably result in
a highly integrated science and technology realm. One of the motivations
for this development is the growing impact of humans
on the Earth’s system and, more importantly, the necessity
to provide solutions while also
recognizing the impact of the relevant social
drivers and their consequences for the changes
that are occurring. Materials are derived
from natural resources, and material
sufficiency has become as important as energy
efficiency with efforts towards a circular
materialist economy, where the materials are
reused and to drawdown from the natural resources base. One of the critical
components in transferring an idea to application
is that of the design. The design is the process
of translating an idea into detailed information
from which a product can be manufactured. The starting point in
design is a market need, and the end point is the full
specification of a solution that fills the needs. While many aspects of
the natural principles are beyond our understanding,
a significant progress has been made in elucidating
the underlying principles. In a highly
interdisciplinary exercise, much real scientists
and engineers work together to reverse
engineer these principles. Making biomimetic
materials and systems requires not only understanding
of the basic principles, but also modeling,
graphic simulation, fabrication of the
materials and systems, and ultimately physical
implementation of the resulting technology. But let’s go back in time. Perhaps the most famous
story related to biomimetics is that of the Swiss
inventor, George de Mestral. In 1941, de Mestral
was on a hunting trip and noticed that both his pants
and his Irish pointers hair were covered in the burs
from a burdock plant. Being curious from
a very early age, de Mestral decided to study
the burs under microscope, more out of curiosity
than because of a business opportunity. What de Mestral
saw were thousands of tiny hooks that
efficiently bound themselves to nearly any fabric. Being inspired by
science, de Mestral realized that, if
he could create a synthetic form of this fabric,
it would allow for a new way to fasten things, a middle
ground between buttons, zippers, and simply
sewing stuff together. His idea was to take the
hooks he had seen in the burs and combine them with
simple loops of fabric. The tiny hooks would
catch in the loops, and things would
just come together. In 1958, he was granted a
patent for his invention for what would later
become known as Velcro. The principles of operation
of all biomimetic materials rely on capturing the
essence of biogenic systems in an attempt to emulate
their functionality by intentional modulation
of their structure and composition. The hierarchical and
mechanistic traits that enable responses
to environmental stimuli are central to advancement
of the biomimetic science as they inspire the design
of durable artificial architectures. Some of the principles
can be harnessed to make miniature devices
that can fly like a dragonfly, adhere to walls like a gecko,
adapt in texture, pattern, and shape of the
surroundings like octopus, process complex three
dimensional images in real time, recycle power for
operation and locomotion, self replicate or self repair, grow
using surrounding resources, or generate and store energy. Plants, for instance,
have prevailed and adapted to different climates by
continually perfecting energy conserving mechanisms
for dispersal that utilize spatial temporal
gradients in temperature, light, pressure, and humidity. Some futuristic
applications can also be envisaged, such
as those that mimic the motility of a tumbleweed. Sophisticated robotic
tumbleweed-like devices could use the wind to
operate on their own for years, traversing thousands
of miles of desertscape, using only the way
to send information on the desert conditions. Since Mars has its
own wind, which you can hear on
this slide, making a Rover that has the
structure of a tumbleweed is an attractive idea to
design a vehicle which can travel great distances
with minimal power. As a second example,
this tumbleweed inspired prototypical mine detonator
on the last picture here is composed almost entirely
of bamboo and biodegradable plastics with a skeletal
structure of spiky plungers that resembles a giant spherical
tumbleweed from another planet. Through evolution over
millions of years, nature introduced power
efficient solutions that use air or air currents. Mimicking these solutions could
improve our lives and the tools we use. Trees disperse their seeds by
using aerodynamic principles to passively travel
with aid of wind, and these principles
have been used in devices from boomerang to gliders,
to helicopter blades, to aircrafts, and drones. Maples, like many long
dispersal tree seeds, rely on wind, upward
currents, and gusts to spread their seeds
over long distances that can reach several kilometers. The wind seed of a
maple, called samara, autogyrates as it falls. The spiral motion is insensitive
to the initial conditions and is stabled against
wind disturbances. So last spring, I actually
collected some of these seeds here in front of
Radcliffe, and I would like to show you how this happens. So these are the seeds,
and if we throw them, they start to
rotate for a reason. The interesting point here
is, regardless how do you throw them in the air, they
always stabilize their motion and go into perfectly
steady descent. So if you throw them. So maple seeds
are able to rotate because of their
structure, because of their center of gravity,
which is determined by the position
of the heavy nut, is located at the base
of the wing shaped seed. It has been observed that,
despite their small size and slow velocities, these seeds
are able to generate with lift, being able to remain in
the air for longer times than other non-rotating seeds. A main puzzle here
has been to understand exactly how the seed settles
into their steady descent. This stable autorotation
of maple seeds or other similar
rotary seeds depends on the interplay between their
three dimensional inertial and aerodynamic
properties, which result in unexpected
high lift forces despite their small
size and slow velocity. The generation of so-called
stable leading edge vortex similar to that observed
in hovering insects, bats, and some birds has
been shown to be responsible for such
high lift force. Robotic models– seeds
that have been recently used to accurately
predict the presence of a strong tornado-like
vortex on top of the maple seed wings
that elevates the lift and increases their dispersal
distance from the tree. So these lessons
learned from the maples and other similar seeds
have been already used as technology in the design
of unmanned aerial vehicles, quadcopters, and drones. The maple seeds, for
example, were the inspiration for a new kind of
flying machine that could be useful for military
information gathering. Lockheed Martin’s intelligent
robotics laboratories developed an unmanned craft
to replicate the motion. The device, named
Samarai, has only two moving parts and a camera. It can be controlled
by remote control or by an app on a phone. Planet Earth has been
called the blue planet due to the abundant
water on its surface. Water is the most
abundant resource in the natural
environment, yet about 97% of the total water on
earth is sea water. The fresh water that is
directly available to humans makes up only
between 0.4% and 2%, and comes mainly from frozen
glaciers and polar ice caps, liquid groundwater,
or aerial humidity. In a recent global risks report,
water scarcity has been ranked has one of the highest
environmental and societal risks. It is estimated that 2/3
of the world population will experience
water stress by 2025. Approximately one billion
people live without access to clean water
resources in rural areas of African, Asian, and
Latin American countries, turning the issue of water
shortage and scarcity into a major global concern. Using an ensemble
of climate models and socioeconomic scenarios,
the World Resources Institute predicts that 33 countries
will face extremely high water stress by 2040. The businesses, farms, and
communities in Chile, Estonia, Namibia, and Botswana could face
especially significant increase in water stress by 2040,
and these countries will become more vulnerable
to water scarcity than they are today. 14 out of 33 most water
stressed countries in 2040 are in the Middle East. The region, already the least
water secure in the world, draws heavily upon groundwater
and desalinated seawater, and faces exceptional
water related challenges for the foreseeable future. With regional violence
and political turmoil commanding global
attention, the water issue may seem a tangential problem. However, looking into
the future and according to the US National
Intelligence Council, the water scarcity will put
key North African and Middle Eastern countries at greater
risk of instability and state failure, and will distract them
from foreign policy engagements with the US. I live in the Emirates,
and although this country is only about 45 years
old, the main cities here are an urban jungle– are very
similar to other metropolises like New York City or Shanghai. So if you drive only about
10 kilometers from here, you will encounter a very
different environment, the Arabian desert. And there is no
other place on Earth where the contrast between
the urban and the natural is so stark. It is the fourth largest
desert in the world and the largest in Asia. The climate here is hot and
dry, with only about 100 millimeter rainfall per year. Miles and miles of
nothing but sand and wind, yet the desert is
not a deserted place. In many regions, fog and
dew represent regularly occurring phenomena and
have a substantial impact on the hydrology and ecology
of the local vegetation. Over several billion
years of evolution, the nature has helped desert
organisms evolve and survive in an extremely hostile
and arid environment by harmonizing the
structure and function, and by making use
of minimal resources to attain maximum performance. Can we learn something from
these amazing creatures? Meet the standard scarab beetle. I think Annie would
love this part. It thrives in the
Namib, a coastal desert in Southern Africa, one of the
most arid habitats on earth. With less than 13 millimeter
rainfall per year. The standard scarab beetle
is able to harvest water on its bumpy back
by a combination of hydrophilic,
or wetable, areas on a hydrophobic, or
non-wetable, background. So what happens is,
early in the morning, when the dew in
which fog settles over the dunes, the beetle
climbs the dune peaks and positions its body in a way
that facilitates dew formation. The water condenses on
the wetable regions, and once droplets
reach critical size, they slide down to
non-wetable regions, and the beetle slurps up
the water thus formed. Inspired by nature,
there are now extensive efforts being made
to utilize this as a design principle, and it has been
already successfully replicated for fog interception
to provide clean water to human settlements
in arid regions. These technologies rely upon
fog water droplet deposition onto nylon mesh
or Teflon fibers. These materials
allow condensation of droplets on their surfaces,
but resist complete wetting. Schemes of this kind have
been successfully implemented in desolate desert areas
in countries including South Africa,
Namibia, and Atacama desert in northern Chile. Several lizard
species and tortoises that live in arid areas
use similar principles to harvest moisture from
humidity fog, dew, or rain. Bodies of lizards, such as
the Australian thorny devil, Arabian [INAUDIBLE],, and
the Texas horned lizard, have independently
developed body surfaces that are covered with
honeycomb-like structures that render the surface super, super
wetable, super hydrophilic, and increase the condensation
of air humidity by about 100%. The water spreads and is
soaked into a capillary system in between scales,
which transports the water to the mouth,
where it is ingested. The combination of
super wetability, micro ornamentation, and
the semitubular capillaries allows for passive or
directed water transport for their survival. Do not mess with these guys,
especially the last one on the right. Indigenous plants found in
arid and semi-arid locations readily cope with an
insufficient access to fresh water. Fog episodes occur frequently
in many of these regions and help to augment
the water supplies for native botanic species
through dew and fog collection, as well as
water vapor absorption. In addition to the adaptive
characteristics that minimize the water
loss, some species appear to use fog as an
additional water supply by using spines that
fulfill multiple functions. The bunny ear cactus shown here
has an efficient fog collection system composed of
well distributed clusters of conical spines. Each spine has three
integrated parts that have different surface
structures and different roles in the fog collection process. The fog collection ability
of these and some other cacti is believed to be driven by
the gradients in free surface energy and the so-called
Laplace pressure. The surface wetting
properties are a combination of surface
chemistry and surface structures. Their underlying
benefits are manyfold and range from prevention
of settling of pathogens to ensuring floating
ability in aquatic plants, to facilitating the catching
of prey by carnivorous plants. In 1997, two German
scientists published the paper on the purity of sacred lotus
and described what later became known as the lotus effect. If you take a close look at
the surface of a lotus leaf, you’ll discover a double
layer of textures. Waxy microscopic
bumps are covered in nanoscale sized hairs which
strap a thin film of layer. When the rain droplets
touch the Lotus leaves, they remain spherical, which
allows the droplets to bounce around until they fall
off the leaf, which stays dry and clean. This self-healing effect can be
also found in other species– plant species, birds,
and even insects. This phenomenon has
aroused great interest for its potential
for applications in self-cleaning materials in
a number of different fields. A deeper knowledge on how these
services attain the property, which is now referred to
as superhydrophobicity, is key to reproducing
this natural effect in glasses for windows,
clothes, and other materials. A particularly important
application of this effect is in preparation of
self-cleaning superhydrophobic coatings for solar cells, which
could solve a major problem with increased efficiency
of solar cells over time, especially in arid regions,
which are also endowed with highest insulation. You will be surprised
to know that there are plants out there that do not
even require soil to survive. Perhaps you’re familiar with
the so-called air plants, such as the tillandsia,
which are biologically referred to as aerophytes. These peculiar plants
make good house plants due to their minimal water
and solar requirements. They obtain moisture
and nutrients from the air and rain. They usually grow
on other plants, but are not parasitic on
them, and some can even live on mobile sand dunes. So I did bring some of
these plants for you, and you will notice
something that is not characteristic
for other plants, which is the shape of the leaves. So they have very narrow
leaves shaped like a trough, and this serves for
collection of water. There you go. So we can possibly learn
something from that and make a similar system
that can be efficient water collectors, especially based
on the shape of the leaves and the surface of these leaves. Going to the next slide,
nature has devised mechanism for active locomotion of
plants, typically observed with rapid movements
for prey and defense, or with very slow movements
during the growth. One of the frontiers of the
contemporary material science research is the design of
a new advanced activating materials which mimic the
motility and are capable of fast, reversible, and
controllable mechanical motion in response to external
stimuli, such as heat, light, magnetic field,
or electric field. The research efforts
in this field are driven by the potentials
for utility of such motion to perform mechanical work
which could have far reaching technological implications as
mechanically active elements– for example, in the future,
micro and nano robotics, which will be soft, organic,
and human-like. The remarkable ability of
geckos to climb vertical walls and ceilings has inspired
philosophers, scientists, artists, and layman
for over two millennia. Aristotle noted the
ability of geckos to run up and down
a tree in any way, even with their head downwards. Geckos use millions
of adhesive hairs on their toes to climb
vertical surfaces at speeds of over 1 meter
per second, which is about two miles per hour. Climbing presents a
significant challenge for an adhesive requiring both
strong and firm attachment, and easy and rapid removal. The attempts to mimic
the gecko toe pads is one of the endeavors
of the fascinating field of evolutionary
nanotechnology, which focuses on developing new
functional and smart materials by utilizing design
principles that have been developed throughout
the evolution in nature. The impressive adhesive
properties of the geckos toe pads have been attributed to
the nature [INAUDIBLE] design of hierarchical biological
structures realized with fine hairs on the
gecko’s feet, which results in an
unmatched demonstration of the power of adhesion. Gecko toes are now well studied,
and their sticky properties have inspired some
incredible technologies, such as stitch free
ways to seal wounds and sticky hand-held paddles
that may help soldiers scale walls someday. The fascination with the
mechanism of adhesion has resulted in several
attempts to develop and test new synthetic dry adhesive
materials inspired by the gecko toe pads. However, the ultimate goal of
creating a perfect mimic that would reach the performance
of natural gecko foot hairs has not accomplished yet, which
has even the brought dispute over the originally proposed
mechanisms of adhesion. To disseminate, some
plants have become capable of active migration
by reversibly changing their shape, and have
developed systems to disperse by creeping,
crawling, ratcheting, buckling, and slithering. Other plants have
developed mechanisms for passive motility, where
their seats can snap, buckle, or explode to disperse,
or burrow themselves in the soil in response to
periodic changes in humidity or temperature. Hydroresponsive
plants, for instance, utilize fluctuations
in aerial humidity to enhance seedling
survival and represent an alternative approach
to environmental energy transduction, because the
hydromotility does not require light or
heat and is driven by slow diffusion controlled
processes that elicit reactions on longer timescales. A multitude of
approaches to realization of biomimetic moving
devices has been advanced through the design
of single molecules, polymers, and composites, where external
stimulation by heat, light, humidity, or magnetic
or electric fields uses structural changes to
drive microscopic motility. When in arid conditions,
some grass [INAUDIBLE] commonly undergo torsional
motion for burial. For example, the [INAUDIBLE]
of grasses such as the needle and thread grass are
effective drillers that are capable
of self cultivation by propelling themselves
into the soil. Resurrection plants,
such as the spike moss, are famous for their ability
to survive extreme dehydration and dessication. During the dry
season, the branches curl inwards, forming
a dead looking ball. When dehydrated, the
plant can be uprooted and become tumbleweed that blows
along the ground with the wind. When moistened, the
plant is coming out of the dormant state induced
by the severe dehydration and opens up. In my lap, we have used
some of these principles to prepare materials which
are able to drill and burrow themselves into the surface in
response to periodic changes in humidity. In the example shown here,
we have prepared the material that mimics this behavior and
can open and close reversibly when it is exposed to water. It can also feel the
presence of a human and can move autonomously
by using only the gradient in aerial humidity. Such hydroscopic materials
have the advantage of long lasting reversible
activation in absence of light and without thermal or
photochemical degradation. Prospective applications
range from power generators and smart textiles to
artificial muscles and sensors. Some of the most
fascinating phenomena that have inspired
biomimetic research are related to the
ability of living systems to use or to generate light. Light is eternal, but ethereal. Light does not require
contact, and therefore provides means
for remote control to biological or
artificial systems. Light interacting
biological structures reflect the uniqueness of
the nature’s optical design, but they also suggest
broad innovation in nature’s use of materials
and its manipulation of light. And if we can just have
the lights dimmed, please. This is our planet, and
if you look very closely, you might see a strange blue
glow off the coast of Florida– when Florida comes
into the picture. This bright blue
glow in the ocean is produced by a subgroup of
algae called dinoflagellates, which are the main
eukaryotic organisms that are capable of
generating cold light. So that would be somewhere here. You can see this glow. When their population
are dense, disturbance of the water during night causes
bright blue bioluminescent displays that have been
reported since at least 500 BC and are known to occur globally. Bioluminescence, the phenomenon
of biological generation of visible cold light by
the excitation of chemically produced excited
states, has been documented as the early as
Aristotle’s De Anima about 350 BC. It has inspired chemists,
writers, artists, and laymen for thousands of years. It is displayed by a number
of organisms, including certain species of bacteria,
insects, jellyfish, mushrooms, worms, and squid. There are about 70
biological families of lower organisms spanning
over 250 genera which are known to display bioluminescence. Only the family of beetles
known as fireflies, for example, contains five
genera in about 2,000 species. So in the bioluminescence
world, the core physical process of these natural phenomena
is energy of transduction by which living
organisms use enzymes to convert the chemical
bond energy of ground state reactants for electronic
excitation of the reaction products. The chem excited
products subsequently emit light in the visible
region of the spectrum, which is used to communicate signals. The bioluminescence is used
for communication, prey, or defense. So in the bioluminescence,
there are these creatures, such as the sea slugs,
which are the good ones. And there are the bad ones,
such as these dragon fish, and, of course, there
are the ugly ones. And this would be the ugly ones. The type locality of this
worm, called diplocardia longa, is a small town in
Georgia in the US. Its body fluids and
the sticky slime that the worm secretes when
stimulated emit a bluish glow. The nature of the
emitting chemical species, however, remains uncertain. Also, there are the
scary ones, as well. So this fish, known
as photoblepharon, using luminescent
bacteria under its eyes. You don’t want to meet
this guy in a dark alley, but it is scary because it’s
very really tiny and harmless. So the bioluminescence has
been utilized and provided an irreplaceable analytical
method with precision on a picomole range– this
is 10 to the minus 12– and evolved into one of the
first non-invasive methods for visualization of cell
and tissue organization. The bioanalytical techniques
based on bioluminescence have become some of the
most versatile and powerful analytical tools developed
in the 20th century. They are nowadays extensively
used for in vivo imaging, for monitoring of cell
proliferation, protein folding, and secretion, environmental
research, food quality control, and protein
and genetic engineering. The bioanalytical techniques
based on bioluminescence are sensitive, reliable,
quantitative, rapid, non-invasive, and generally
come with a high signal to noise ratio. However, some of the most
recent biomimetic applications in material science are focused
on the firefly lanterns, which help to very
efficiently uncouple the light from the body and to
deliver strong optical signals in sexual communication. The high transmission
nanostructures of the firefly
lantern cuticle have become biological inspiration
for highly efficient LED illumination. Such biologically inspired
LED lenses substantially increase the light transmission
over a visible range compared to conventional
anti-reflection coatings. One of the most
remarkable consequences of the orders and patterns that
are generated spontaneously is the so-called
structural color. The description of
these optical effects is as old as Robert Hooke’s
famous book, Micrographia, published in the
17th century, where he presents microscopic
images of brilliant feathers of peacocks and
ducks, and reports that the colors
of their feathers are destroyed by
a drop of water. When a matter is illuminated
with white light, we see color. Only the reflected light is
of a particular wavelength that is detectable by our eyes. There are two ways to eliminate
the remaining wavelengths– by absorption, as is
the case with colored materials such as
pigments, dyes, and metals, where the color is due
to the exchange of energy between the light and electrons. In the second case, the light
is reflected, scattered, and deflected, and it doesn’t
reach the eyes because of the physical phenomena that
happen on the specific surface structures. In nature, these
colors are enhanced by thin film and multi-layer
interference, diffraction ratings, light scattering,
or photonic crystals. So if you look at
these pictures, you see the different
structures in the blue region here than in the green region. And there is a further
degree of complexity, because if you zoom
in these structures, you will see even tinier
and finer structures that actually all contribute to
light without any pigmentation. Some insects and
butterfly species use similar complex
photonic band gap structures that prevent propagation
of a band of wavelengths through them, and thus cause
very strong color reflections. In butterflies such as
the blue morpho butterfly, the visibility of
up to one half mile is attributed to
photonic structures that are formed by discrete
multiple layers of cuticle and air. The butterflies use light
interacting structures on their wing scales
to produce color. The cuticle on their scales is
composed of transparent kited and air layered
structures with size from the nanoscale
to the micro scale. These multi-scale
structures cause light that hits the
surface of the wing to deflect and interfere. Cross rips that
protrude from the sides of the ridges on the wing scale
diffract incoming light waves, causing the waves to spread as
they traveled through spaces between the structures. The varying heights of
the wing scale ridges 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, thermal
regulations, and signaling. So before I go into the
last part of my talk, I would just like
to briefly introduce two last examples that come
from faculty who are now here at Harvard, where there
is a very active research in this biomimetic field. The first is a sessile
deep water sponge known as the Venus flower basket. It’s called Venus
flower basket because it has a couple of [INAUDIBLE] that
remain trapped there forever, for life. So this is a symbiotic organism. This impressive structure was
started by Jonah Eisenberg here at Harvard, and
all of it is essentially made of the fine fibers of
glass with diameter close to that of a human hair. It could withstand
enormous pressure at the seafloor due to
a specific hierarchical structure, which
embodies reinforcements at multiple levels. The second example comes from
the laboratory of [INAUDIBLE].. It explains how tendrils of
cucumbers and some other plants work. Once it is attached
to a solid surface, the tendril shortens into
a helix, pulling the plant, but rather than twisting in
only one direction, which is impossible without twisting
the plant on the other hand, the two halves of
the coil section curl up in opposite
directions, separated by an uncoiled stretch
so there is no net twist. In addition to being a
significant component of a bio inspired
architectural design, a portion of the
biomimetic research is proprietary to
specialized national defense labs that develop
stealth technologies and is not available to public. The stealth or low
observable technology covers a combination
of techniques that range from aircraft shaped
to special, low observable coatings that are used to make
personnel or military objects or vehicles less visible or
invisible to radar, infrared, sonar, and other direct
detection methods. The very early
stealth technologies involved the concept
of camouflage for reducing the
visual signature by making appearance
of an object blend into the
visual background. Increased capability of the
detection and interception technologies required
advanced materials that either deflect or
absorb electromagnetic waves from tracking devices. For example, central to the
design of the F-35 joint strike fighter design is
the application of composite materials such
as composites of fiber mats and polymers to reduce
observability and maintenance costs while avoiding
applications of stealth coatings. Future increases
in human welfare will be driven by the increased
understanding and mastery of the natural world, and the
materials the scientists are posed to expand the
frontiers of human knowledge by exploring these secrets,
but that globalization has a dark side, too. We are living in
an urban century, and demographic forecasts
indicate that world population will reach 9 billion
by 2050, which is an increase of 2
billion than at present. Being a phenomenon of physical
and cultural restructuring, the globalization will have
complicated and far reaching social, aesthetic,
economic, and physical, and political effects. Environmental challenges
facing the planet are complex, and their impact on the natural
world and on human society can be catastrophic. Climate change, loss
of natural resources, declining biodiversity,
deforestation, and desertification, changes
in the carbon, nitrogen, and phosphorus cycles, sea
level change, and pollution each pose enormous problems, both
regionally and globally, and indicate a dystopian future. So on this slide,
you can see some of the species that are already
extinct or close to extinction. These challenges are
intricately interwoven with issues of human health,
population, migration, water, food, and energy
security, and inevitably the potential for conflict. They require a broad
interdisciplinary approach to understand them and
to provide solutions. Many of these challenges
already have had or will have direct
impact locally. Our planet is now in the
midst of the sixth wave of mass extinction
of plants and animals in the past half billion years. We are experiencing the
worst state of species die offs since the loss of
dinosaurs 65 million years ago. It is estimated that
we are losing species 1,000 to 10,000 times the
background rate, which is 1 to 5 species per year. These slides that I
showed shows only a few of these species that are
close to extinction or extinct, and this is only a small
fraction of the species that we are aware of. There are many more
species, both small and big, that we lost forever
without us even knowing that they ever existed. So there are several
questions that I will pose at the end of my talk. Can we reverse this process? Can we prevent, slow
down destroying, or remedy nature while
continuing to increasingly explore its resources? And does humanity really
need a backup planet? Thank you. [APPLAUSE]

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