Biology for Engineers, Unit-IV______.pdf

Brief biology for engineers explains how to design and construct biological systems to solve engineering problems, covering topics like cellular mechanisms, genetic engineering, biomechanics, and synthetic biology. It involves understanding fundamental biological processes to develop sustainable solutions in fields such as medicine, agriculture, and materials science, using engineering principles to modify and build living systems for new functions, notes the Engineering Biology Research Consortium (EBRC) and the Institute of Biological Engineering (IBE).

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UNIT -4
NATURE –BIO INSPIRED MATERIALS AND MECHANISMS

Syllabus: Nature-Bio inspired Materials and Mechanisms: Echolocation
(ultrasonography, sonars), Photosynthesis (photovoltaic cells, bionic leaf). Bird flying
(GPS and aircrafts), Lotus leaf effect (Super hydrophobic and self-cleaning surfaces),
Plant burrs (Velcro), Shark skin (Friction reducing swim suits), Kingfisher beak (Bullet
train). Human Blood substitutes - hemoglobin-based oxygen carriers (HBOCs) and per
fluorocarbons (PFCs).

Nature –Bio inspired materials and mechanisms
Echolocation:
Echolocation is a specialized process of orientation used by bats. Bats emit high frequency
sound waves while navigating, and process the echo that comes back from obstacles. This
method assists prey location and capture.
Bats are capable of avoiding obstacles that they encounter, even in complete darkness. This is
because they emit ultrasound (high frequency sound) and analyse the echo produced when the
sound hits objects on their path. This article describes the hunting flight of bats and how
echolocation is useful in prey capture. Prey capture without the aid of echolocation by some
bats is also described.

The Discovery of Echolocation:
During the year 1790, Lazzaro Spallanzani, an Italian naturalist, first observed that bats were
able to avoid obstacles while flying even in total darkness. He also found that despite the
surgical removal of eyes, bats could fly without bumping into obstacles. Later, Charles Jurine,
a Swiss zoologist, plugged the ears of bats and observed their inability to perform these correct
orientations. Spallanzani repeated these experiments and obtained similar results. Both of them
concluded that bats could 'see' through their ears! The French naturalist Cuvier disagreed

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with this statement. He explained that a sense of touch in the wing membrane caused the bats
to avoid obstacles. In 1920, Hartridge, a British physiologist put forward the hypothesis that
bats emit ultrasound and listen to the echoes of these sounds. After 18 years, the American
zoologist, Donald R Grifl'm along with Pierce, a physicist, used a microphone sensitive to
ultrasound and demonstrated that bats do emit trains of ultrasonic pulses while flying. They
showed that the number of sound pulses increased as bats approached obstacles on their flight
path. They also noticed that the bat's mouth was always open when the sounds were emitted.
Griffin continued the experiments and found that closing the mouth of the bat resulted in
disorientation. He established that bats emit sounds through their mouths. Hence, Griffin who
coined the term 'echolocation' in 1938. In 1958, he published his classic book, 'Listening in
the Dark' which documents many details about the discovery of echolocation. Echolocation is
one of the methods of orientation mainly used by the micro chiropteran or insectivorous bats.
While flying, these bats emit high frequency ultrasound. These sound pulses hit obstacles like
rocks, trees, walls etc. and their echoes are heard by bats. By analysing these echoes, bats are
able to find their way even deep into underground caves in which there are absolutely no light.

Ultrasonography
Ultrasonography uses high-frequency sound (ultrasound) waves to produce images of
internal organs and other tissues. A device called a transducer converts electrical current into
sound waves, which are sent into the body‘s tissues. Sound waves bounce off structures in
the body and are reflected back to the transducer, which converts the waves into electrical
signals. A computer converts the pattern of electrical signals into an image, which is
displayed on a monitor and recorded as a digital computer image. No x-rays are used, so
there is no radiation exposure during an ultrasonography.

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Fig. 4.1: Sonography of kidney

Procedures for Ultrasonography:
If certain parts of the abdomen are being examined, people may be asked to refrain from
eating and drinking for several hours before the test. For examination of female reproductive
organs, women may be asked to drink a large amount of fluid to fill their bladder.
Usually, the examiner places thick gel on the skin over the area to be examined to ensure
good
sound transmission. A handheld transducer is placed on the skin and moved over the area to
be evaluated.
To evaluate some body parts, the examiner inserts the transducer into the body—for
example, into the vagina to better image the uterus and ovaries or into the anus to image the
prostate gland.
The examiner sometimes attaches the transducer to a viewing tube called an endoscope and
passes it into the body. This procedure is called endoscopic ultrasonography. The endoscope
can be passed down the throat to view the heart (trans esophageal echocardiography) or
through the stomach to view the liver and other nearby organs. After the test, most people
can resume their usual activities immediately.

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Ultrasound images are acquired rapidly enough to show the motion of organs and structures
in the body in real time (as in a movie). For example, the motion of the beating heart can be
seen, even in a fetus.
Ultrasonography is effectively used to check for growths and foreign objects that are close to
the body‘s surface, such as those in the thyroid gland, breasts, testes, and limbs, as well as
some lymph nodes.
Ultrasonography is effectively used to image internal organs in the abdomen, pelvis, and
chest. However, because sound waves are blocked by gas (for example, in the lungs or
intestine) and by bone, ultrasonography of internal organs requires special skills. People who
have been specifically trained to do ultrasound examinations are called sonographers.
Uses of Ultrasonography: Ultrasonography is commonly used to evaluate :
Heart: For example, to detect abnormalities in the way the heart beats, structural
abnormalities such as defective heart valves, and abnormal enlargement of the heart‘s
chambers or walls (ultrasonography of the heart is called echocardiography)
Blood vessels: For example, to detect dilated and narrowed blood vessels
Gallbladder and biliary tract: For example, to detect gallstones and blockages in the bile
ducts
Liver, spleen, and pancreas: For example, to detect tumors and other disorders
Urinary tract: For example, to distinguish benign cysts from solid masses (which may be
cancer) in the kidneys or to detect blockages such as stones or other structural abnormalities
in the kidneys, ureters, or bladder
Female reproductive organs: For example, to detect tumors and inflammation in the
ovaries, fallopian tubes, or uterus
Pregnancy: For example, to evaluate the growth and development of the fetus and to detect
abnormalities of the placenta (such as a misplaced placenta, called placenta previa).

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Variations of Ultrasonography:
Ultrasonography can also be used to guide doctors when they remove a sample of tissue for a
biopsy. Ultrasonography can show the position of the biopsy instrument, as well as the area
to be biopsied (such as a mass). Thus, doctors can see where to insert the instrument and can
guide it directly to its target.
Ultrasound information can be displayed in several ways:
A-mode: As spikes on a graph (used to scan the eye)
B-mode: As a 2-dimensional anatomic images (used during pregnancy to evaluate the
developing fetus or to evaluate internal organs)
M-mode: As waves displayed continuously to show moving structures (used to evaluate the
fetus's heartbeat or to evaluate heart valve disorders)
B-mode ultrasonography is most commonly done.
Doppler ultrasonography:
Doppler ultrasonography uses changes that occur in the frequency of sound waves when they
are reflected from a moving object (called the Doppler effect). In medical imaging, the
moving objects are red blood cells in the blood. Thus, Doppler ultrasonography can be used
to evaluate
 Whether blood is flowing through blood vessels
 How fast it flows
 Which direction it flows in Doppler ultrasonography is used
 To evaluate how well the heart is functioning (as part of echocardiography)
 To detect blocked blood vessels, especially in leg veins, as in deep vein thrombosis,

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when veins are blocked by a blood clot
 To detect narrowed arteries, especially the carotid arteries in the neck, which carry
blood to the brain.
Spectral Doppler ultrasonography: This procedure shows blood flow information as a
graph. It can be used to assess how much of a blood vessel is blocked.

Duplex Doppler ultrasonography: This procedure combines spectral and B-mode
ultrasonography.

Color Doppler ultrasonography: For this test, color is superimposed on the shades-of-gray
image of blood flow produced by Doppler ultrasonography. The color indicates direction of
blood flow. Red may be used to indicate flow toward the transducer, and blue may be used to
indicate flow away from the transducer. The brightness of the color indicates how fast the
blood is flowing.
Color Doppler ultrasonography can help assess the risk of stroke because it helps doctors
identify and evaluate narrowing or blockage of arteries in the neck and head. The procedure
is useful for evaluating people who have had a transient ischemic attack or stroke and people
who have risk factors for atherosclerosis but no symptoms. Color Doppler ultrasonography is
also used to assess blood flow to internal organs and tumors.
Disadvantages of Ultrasonography:
Diagnostic ultrasound is a safe procedure that uses low-power sound waves. There are no
known risks. Ultrasound is a valuable tool, but it has limitations. Sound waves don't travel well
through air or bone, so ultrasound isn't effective at imaging body parts that have gas in them or
are hidden by bone, such as the lungs or head. Ultrasound may also be unable to see objects
that are located very deep in the human body. To view these areas, your health care provider
may order other imaging tests, such as CT or MRI scans or X-rays.

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Sonar technology:
Sonar (sound navigation and ranging) is a technology that uses acoustical waves to sense the
location of objects in the ocean. The simplest sonar devices send out a sound pulse from
a transducer, and then precisely measure the time it takes for the sound pulses to
be reflected back to the transducer. The distance to an object can be calculated using this time
difference and the speed of sound in the water (approximately 1,500 meters per second). More
sophisticated sonar systems can provide additional direction and range information. Sonar was
developed during World War I as an aid in finding both submarines and icebergs. Major
improvements were made on this technology during World War II, and eventually scientists
adapted the highly sensitive equipment for use in oceanographic research.
There are two types of sonar: active and passive. Passive sonar is a listening device only;
sound waves produced by another source are received and changed into electrical signals for
display on a monitor. Active sonar, on the other hand, sends out sound waves in pulses;
scientists then measure the time it takes these pulses to travel through the water, reflect off of
an object, and return to the ship. Because scientists know how fast sound travels through water,
they can easily calculate the distance between their ship and the object they are interested in,
such as a ship or animal. They can also use the return echo to identify the object that the sound
reflected off of. Whales, dolphins, and bats use echolocation, a natural type of sonar, in order
to identify and locate their prey. These animals emit ―clicks,‖ sounds that are reflected back
when they hit an object.
Principle of Sonar: It uses echoes in to determine the sea-depth and locating the presence
of objects underwater.
Working of Sonar: i) It consists of a transmitter and a detector and is installed in a ship or a
boat. ii) The transmitter on SONAR produces and transmits powerful ultrasonic waves. iii) The
ultrasonic waves travel through the water and after striking the target the beam is reflected
from the seabed and is received by an underwater detector (mounted on the ship). iv) The
detector then converts the waves into electrical signals which are properly interpreted. v) The

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time interval between transmission and reception of the signal is also noted (Fig 3).

Fig. 4.2: The working model of Sonar using a ship
Photosynthesis
Introduction: All organisms, including humans, need energy to fuel the metabolic reactions of
growth, development, and reproduction. But organisms can't use light energy directly for their
metabolic needs. Instead, it must first be converted into chemical energy through the process of
photosynthesis.
What is photosynthesis?
Photosynthesis is the process in which light energy is converted to chemical energy in the
form of sugars. In a process driven by light energy, glucose molecules (or other sugars) are
constructed from water and carbon dioxide, and oxygen is released as a by-product. The
glucose molecules provide organisms with two crucial resources: energy and fixed organic
carbon.
 Energy. The glucose molecules serve as fuel for cells: their chemical energy can be harvested

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through processes like cellular respiration and fermentation, which generate adenosine
triphosphate-ATP, a small, energy-carrying molecule—for the cell‘s immediate energy needs.
 Fixed carbon. Carbon from carbon dioxide—inorganic carbon—can be incorporated into
organic molecules; this process is called carbon fixation, and the carbon in organic molecules
is also known as fixed carbon. The carbon that's fixed and incorporated into sugars during
photosynthesis can be used to build other types of organic molecules needed by cells.

Fig. 4.3: The process of photosynthesis

In photosynthesis, solar energy is harvested and converted to chemical energy in the form of
glucose using water and carbon dioxide. Oxygen is released as a by-product.

The ecological importance of photosynthesis
Photosynthetic organisms, including plants, algae, and some bacteria, play a key ecological
role. They introduce chemical energy and fixed carbon into ecosystems by using light to
synthesize sugars. Since these organisms produce their own food—that is, fix their own
carbon—using light energy, they are called photoautotrophs (literally, self-feeders that use
light).
Humans, and other organisms that can‘t convert carbon dioxide to organic compounds

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themselves, are called heterotrophs, meaning different-feeders. Heterotrophs must get fixed
carbon by eating other organisms or their by-products. Animals, fungi, and many prokaryotes
and protists are heterotrophs.
Besides introducing fixed carbon and energy into ecosystems, photosynthesis also affects the
makeup of Earth‘s atmosphere. Most photosynthetic organisms generate oxygen gas as a by-
product, and the advent of photosynthesis—over 333 billion years ago, in bacteria resembling
modern cyanobacteria—forever changed life on Earth^11start superscript, 1, end superscript.
These bacteria gradually released oxygen into Earth‘s oxygen-poor atmosphere, and the
increase in oxygen concentration is thought to have influenced the evolution of aerobic life
forms—organisms that use oxygen for cellular respiration. If it hadn‘t been for those ancient
photo synthesizers, we, like many other species, wouldn't be here today!
Photosynthetic organisms also remove large quantities of carbon dioxide from the atmosphere
and use the carbon atoms to build organic molecules. Without Earth‘s abundance of plants and
algae to continually suck up carbon dioxide, the gas would build up in the atmosphere.
Although photosynthetic organisms remove some of the carbon dioxide produced by human
activities, rising atmospheric levels are trapping heat and causing the climate to change. Many
scientists believe that preserving forests and other expanses of vegetation is increasingly
important to combat this rise in carbon dioxide levels.

Leaves are sites of photosynthesis
Plants are the most common autotrophs in terrestrial—land—ecosystems. All green plant
tissues can photosynthesize, but in most plants, but the majority of photosynthesis usually
takes place in the leaves. The cells in a middle layer of leaf tissue called the mesophyll are the
primary site of photosynthesis.
Small pores called stomata—singular, stoma—are found on the surface of leaves in most
plants, and they let carbon dioxide diffuse into the mesophyll layer and oxygen diffuse out.

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Fig. 4.4: The sites of photosynthesis
Sites of Photosynthesis:
Each mesophyll cell contains organelles called chloroplasts, which are specialized to carry out
the reactions of photosynthesis. Within each chloroplast, disc-like structures
called thylakoids are arranged in piles like stacks of pancakes that are known as grana—
singular, granum. The membrane of each thylakoid contains green-colored pigments
called chlorophylls that absorb light. The fluid-filled space around the grana is called

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the stroma, and the space inside the thylakoid discs is known as the thylakoid space. Different
chemical reactions occur in the different parts of the chloroplast.
The light-dependent reactions and the Calvin cycle:
Photosynthesis in the leaves of plants involves many steps, but it can be divided into two
stages:
The light-dependent reactions and the Calvin cycle:
The light-dependent reactions take place in the thylakoid membrane and require a continuous
supply of light energy. Chlorophylls absorb this light energy, which is converted into chemical
energy through the formation of two compounds, ATP- an energy storage molecule
and NADPH- a reduced (electron-bearing) electron carrier. In this process, water molecules are
also converted to oxygen gas- the oxygen we breathe.
The Calvin cycle, also called the light-independent reactions, takes place in the stroma and
does not directly require light. Instead, the Calvin cycle uses ATP and NADPH from the light-
dependent reactions to fix carbon dioxide and produce three-carbon sugars- glyceraldehyde-3-
phosphate, or G3P, molecules- which join up to form glucose.

Fig. 4.5: Overview of Photosynthesis
Overall, the light-dependent reactions capture light energy and store it temporarily in the

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chemical forms of ATP and NADPH. There, ATP is broken down to release energy,
and NADPH donates its electrons to convert carbon dioxide molecules into sugars. In the end,
the energy that started out as light winds up trapped in the bonds of the sugars.
Photosynthesis vs. cellular respiration
At the level of the overall reactions, photosynthesis and cellular respiration are near-opposite
processes. They differ only in the form of energy absorbed or released, as shown in the
diagram below.

Fig. 4.6: The process of photosynthesis and cellular respiration
At the level of individual steps, photosynthesis isn't just cellular respiration run in reverse.
Instead, as we'll see the rest of this section, photosynthesis takes place in its own unique series
of steps. However, there are some notable similarities between photosynthesis and cellular
respiration.
For instance, photosynthesis and cellular respiration both involve a series of redox reactions
(reactions involving electron transfers). In cellular respiration, electrons flow from glucose to
oxygen, forming water and releasing energy. In photosynthesis, they go in the opposite
direction, starting in water and winding up in glucose—energy-requiring process powered by
light. Like cellular respiration, photosynthesis also uses an electron transport chain to make a
H
+
concentration gradient, which drives ATP synthesis by chemiosmosis.

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Photovoltaic cells
A photovoltaic (PV) cell is an energy harvesting technology, that converts solar energy into
useful electricity through a process called the photovoltaic effect. There are several
different types of PV cells which all use semiconductors to interact with
incoming photons from the Sun in order to generate an electric current.

Layers of a PV cell
A photovoltaic cell is comprised of many layers of materials, each with a specific purpose. The
most important layer of a photovoltaic cell is the specially treated semiconductor layer. It is
comprised of two distinct layers (p-type and n-type—see Figure 8), and is what actually
converts the Sun's energy into useful electricity through a process called the photovoltaic
effect (see below). On either side of the semiconductor is a layer of conducting material which
"collects" the electricity produced. Note that the backside or shaded side of the cell can afford
to be completely covered in the conductor, whereas the front or illuminated side must use the
conductors sparingly to avoid blocking too much of the Sun's radiation from reaching the
semiconductor. The final layer which is applied only to the illuminated side of the cell is the
anti-reflection coating. Since all semiconductors are naturally reflective, reflection loss can be
significant. The solution is to use one or several layers of an anti-reflection coating (similar to
those used for eyeglasses and cameras) to reduce the amount of solar radiation that is reflected
off the surface of the cell.









Fig. 4.7: Photovoltic cell

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Photovoltaic effect
Photovoltaic cells consist of two or more layers of semiconductors with one layer containing
positive charge and the other negative charge lined adjacent to each other.
Sunlight, consisting of small packets of energy termed as photons, strikes the cell, where it is
either reflected, transmitted or absorbed.
When the photons are absorbed by the negative layer of the photovoltaic cell, the energy of the
photon gets transferred to an electron in an atom of the cell. With the increase in energy, the
electron escapes the outer shell of the atom. The freed electron naturally migrates to the
positive layer creating a potential difference between the positive and the negative layer. When
the two layers are connected to an eternal circuit, the electron flows through the circuit,











Fig 4.8: Photovoltaic cells containing layers of semiconductors
Advantages of Photovoltaic Cells:
 Environmental Sustainability: Photovoltaic cells generate clean and green energy as
no harmful gases such as CO2, NO2 etc are emitted. Also, they produce no noise
pollution which makes them ideal for application in residential areas.
 Economically Viable: The operation and maintenance costs of cells are very low. The

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Cost of solar panels incurred is only the initial cost i.e., purchase and installation.
 Accessible: Solar panels are easy to set up and can be made accessible in remote
locations or sparsely inhabited areas at a lesser cost as compared to conventional
transmission lines. They are easy to install without any interference with the residential
lifestyle.
 Renewable: Energy is free and abundant in nature.
 Cost: Solar panels have no mechanically moving parts except in some highly advanced
sunlight tracking mechanical bases. Consequently, the solar panel price for
maintenance and repair is negligible.
Disadvantages of Photovoltaic Cells:
 The efficiency of solar panels is low compared to other renewable sources of energy.
 Energy from the sun is intermittent and unpredictable and can only be harnessed in the
presence of sunlight. Also, the power generated gets reduced during cloudy weather.
 Long-range transmission of solar energy is inefficient and difficult to carry.
 Photovoltaic panels are fragile and can be damaged relatively easily.
 Additional insurance costs are required to ensure a safeguard of the investments.

Bionic leaf:
One of the most promising developments in the search for renewable energy has been the
artificial leaf. The Artificial leaf, also known as the Bionic leaf, is a silicon-based device that
utilizes the sun and water to generate useable and environmentally beneficial fuels. When
exposed to sunlight; it carries out the same processes of photosynthesis by splitting water
molecules into hydrogen and oxygen to combine with CO 2 and form beneficial
sugars. Through the continual development of complex chemical models and theory
surrounding the artificial leaf, it‘s potential benefits to society can be explored and
implemented on a worldwide scale in the future.
The artificial leaf is a device that manipulates traditional photosynthesis to generate fuel from

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solar energy and water. Photosynthesis is an endothermic reaction as it consumes energy from
the sun, further converting it to functional chemical energy. Water molecules during
photosynthesis are photo-oxidised through the absorption of light energy through a green
pigment; chlorophyll, discharging oxygen and protons. Furthermore, the resulting protons are
then used for the generation of hydrogen. Carbon dioxide is then utilised from the surrounding
air to create intermediate glucose molecules that can be utilised for the growth of the plant by
consuming the previously formed protons and oxygen. Illustrated below in equation 1, is the
chemical equation for photosynthesis:






--------------Equation 1










Fig 4.9: Reaction in the Artificial leaf

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Two half reactions of oxidation and reduction occur during the photosynthetic reaction
transpiring with in the Artificial leaf. These half reactions are essential to producing fuels. By
mimicking the photosynthetic activity of a plant, it pairs the water splitting catalyst; the
oxygen-evolving-complex enzyme, with the bacteria Ralstonia eutropha. This consumes
hydrogen and converts the carbon dioxide in the atmosphere into efficient alcohol based fuels.
The artificial leaf also encompasses an energy absorbing photovoltaic panel made from
silicone that sources its energy from the sun. Both sides of this panel consist of a layer
of cobalt-phosphorus alloy catalysts to power the chemical reaction by utilizing solar energy to
promote the splitting of the water molecules into hydrogen and oxygen molecules. As a result,
a separation of protons and electrons is triggered, which are then apprehended on the chip and
recombined to form hydrogen gas that be stored for subsequent tests or utilized for the
instantaneous production of electricity. The configuration and progression of the artificial leaf
is illustrated In figure.
The formation of hydrogen gas is caused by a reduction of H
+
ions and occurs at the cathode.
Considered as the simplest solar fuel to synthesize, Hydrogen only required the relocation of
two electrons to two protons. However, the reduction of hydrogen must occur stepwise, with
formation of an intermediate hydride ion as a product of the reaction. This is reaction is
illustrated below by equation below









------------------- Equation2
Equation 2: Reduction of H
+
ions at the cathode to form H2
The oxidation of water molecules occurs at the anode. The previously referenced oxygen-
evolving complex performs this reaction by gathering electrons and distributing them to the
water molecules, resulting in the production of molecular oxygen and protons. This half
equation is expressed below in equation 3.








---------------------- Equation 3
Equation 3: Oxidation of water molecules at the anode
By combining the half equations that occur at the anode and the cathode, the overall reaction

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showing the materialisation of hydrogen fuel and oxygen occurring in the Artificial leaf is
represented by the equation below in figure 4:



---------------------- Equation 4
Equation 4: Formation of hydrogen and oxygen from water
In 2015, the original model of the artificial leaf with newly developed catalysts was tested.
This included the nickel-molybdenum-zinc alloy catalyst, which was used in preliminary
studies concerning the function of the artificial leaf under simple conditions and exhibited
increased stability over preceding catalyst designs. In laboratory studies, the authors; Dr. David
Nocera and Pamela Silver; demonstrated that a prototype version of the artificial leaf could
operate continuously for at least forty-five hours exclusive of drop-in functionality. This
prototype also allowed for the conversion efficiency of water to biomass to be approximately
1%; which is comparable to that of natural photosynthesis. Using this knowledge, the first fully
purposeful artificial leaf, dubbed the ‗Bionic Leaf 1.0‘ was developed in late 2015.
Bird flying:
Bird flight is the primary mode of locomotion used by most bird species in which birds take off
and fly. Flight assists birds with feeding, breeding, avoiding predators, and migrating.
Bird flight is one of the most complex forms of locomotion in the animal kingdom. Each facet
of this type of motion, including hovering, taking off, and landing, involves many complex
movements. As different bird species adapted over millions of years through evolution for
specific environments, prey, predators, and other needs, they developed specializations in their
wings and acquired different forms of flight.
GPS:
Global positioning system navigation (GPS) is the fastest growing type of navigation in
aviation. It is accomplished through the use of NAVSTAR satellites set and maintained in orbit
around the earth. Continuous coded transmissions from the satellites facilitate locating the
position of an aircraft equipped with a GPS receiver with extreme accuracy. GPS can be

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utilized on its own for end route navigation, or it can be integrated into other navigation
systems, such as VOR/RNAV, inertial reference, or flight management systems.

There are three segments of GPS: the space segment, the control segment, and the user
segment. Aircraft technicians are only involved with user segment equipment such as GPS
receivers, displays, and antennas. Twenty-four satellites (21 active, 3 spares) in six separate
plains of orbit 12, 625 feet above the planet comprise what is known as the space segment of
the GPS system. The satellites are positioned such that in any place on earth at any one time, at
least four will be a minimum of 15° above the horizon. Typically, between 5 and 8 satellites
are in view.
Two signals loaded with digitally coded information are transmitted from each satellite. The
L1 channel transmission on a1575.42 MHz carrier frequency is used in civilian aviation.
Satellite identification, position, and time are conveyed to the aircraft GPS receiver on this
digitally modulated signal along with status and other information. An L2 channel 1227.60
MHz transmission is used by the military.
The amount of time it takes for signals to reach the aircraft GPS receiver from transmitting
satellites is combined with each satellite‘s exact location to calculate the position of an aircraft.
The control segment of the GPS monitors each satellite to ensure its location and time are
precise. This control is accomplished with five ground-based receiving stations, a master
control station, and three transmitting antenna. The receiving stations forward status
information received from the satellites to the master control station. Calculations are made
and corrective instructions are sent to the satellites via the transmitters.

The user segment of the GPS is comprised of the thousands of receivers installed in aircraft as
well as every other receiver that uses the GPS transmissions. Specifically, for the aircraft
technician, the user section consists of a control panel/display, the GPS receiver circuitry, and
an antenna. The control, display and receiver are usually located in a single unit which also
may include VOR/ILS circuitry and a VHF communications transceiver. GPS intelligence is
integrated into the multifunctional displays of glass cockpit aircraft.

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GPS and Aircrafts:
Scientists have long known that birds navigate using the earth‘s magnetic field. Now, a new
study has found subtle mechanics in the brain of pigeons that allow them to find their way.
A team at Baylor College of Medicine in the U.S. identified a group of 53 cells in a pigeon‘s
brain that record detailed information on the Earth‘s magnetic field, a kind of internal global
positioning system (GPS).
Experiment:
Prof. Dickman and his colleague Le-Qing Wu set up an experiment in which pigeons were held
in a dark room and used a 3D coil system to cancel out the planet‘s natural geomagnetic field
and generate a tunable, artificial magnetic field inside the room. While they adjusted the
elevation angles and magnitude of their artificial magnetic field, they simultaneously recorded
the activity of the 53 neurons in the pigeons‘ brains which had already been identified as
candidates for such sensors.
So, they measured the electrical signals from each one as the field was changed and found that
every neuron had its characteristic response to the magnetic field, each giving a sort of 3-D
compass reading along the familiar north-south directions as well as pointing directly upward
or downward. In life, this could help the bird determine not only it's heading just as a compass
does, but would also reveal its approximate position, the researchers said.
Each cell also showed sensitivity to field strength, with the maximum sensitivity corresponding
to the strength of the Earth‘s natural field, they added. And like a compass, the neurons had
opposite responses to different field ―polarity‖, the magnetic north and south of a field, which
surprised the researchers most of all. Several hypotheses hold that birds‘ magnetic navigation
arises in cells that contain tiny chunks of metal in their noses or beaks, or possibly in an inner
ear organ.
However, the most widely held among them was thrown into question when researchers found
that purported compass cells in pigeon beaks were a type of white blood cell.

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Aircraft mechanism:
The fundamentals of bird flight are similar to those of aircraft, in which the aerodynamic forces
sustain flight lift, drag, and thrust. Lift force is produced by the action of airflow on the wing,
which is an airfoil. The airfoil is shaped such that the air provides a net upward force on the
wing, while the movement of air is directed downward. The additional net lift may come from
airflow around the bird's body in some species, especially during intermittent flight while the
wings are folded or semi-folded (cf. lifting body).
Aerodynamic drag is the force opposite to the direction of motion, and hence the source of
energy loss in flight. The drag force can be separated into two portions, lift-induced drag,
which is the inherent cost of the wing producing lift (this energy ends up primarily in the
wingtip vortices), and parasitic drag, including skin friction drag from the friction of air and
body surfaces and form drag from the bird's frontal area. The streamlining of the bird's body
and wings reduces these forces. Unlike aircraft, which have engines to produce thrust, birds
flap their wings with given flapping amplitude and frequency to generate thrust.
Lotus leaf effect:
The lotus leaf is well-known for having a highly water-repellent, or super hydrophobic,
surface, thus giving the name to the lotus effect. Water repellency has received much attention
in the development of self-cleaning materials, and it has been studied in both natural and
artificial systems.
Understanding of the Lotus Effect:
Super hydrophobic surfaces, which have existed for hundreds of millions of years, are now
back in fashion thanks to Nanotechnology and the Lotus Effect. It has long been known that
Lotus leaves, an aquatic plant of Asian origin, do not get wet. As a result, the rainwater takes
the form of spherical drops when it comes into contact with the surface of its leaves, which
allows it to slide freely taking all dirt with it and keeping the leaf clean and dry, as well as free
of bacterial colonies, despite living in polluted waters. This ―self-cleaning‖ effect, called the
Lotus effect, is also found in other plant species, birds and insects.

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To explain the super hydrophobic behaviour of the Lotus leaves, biologists had to study the
chemical composition and topography of them. Basically, they found that the leaves had two
levels of structures that explained this behaviour: a microstructure level (of the size of microns
or thousands of a millimeter) consisting of surface lumps and a nanostructure level (of the
order of the millionth of a millimeter) formed by small hairs. Both systems are constituted by a
waxy coating, which together makes the surface of a lotus leaf repel water and does not get wet
(super hydrophobic surfaces).
This particular phenomenon, studied by Dettre and Johnson in 1964, inspired by the lotus
flower (scientific name of the Asian lotus: Nymphaea nelumbo), represents the plant's ability to
be super-hydrophobic, that is water repellent, and consequently self-cleaning, thanks to the
particular geometry of the leaf surface and to a covering by a thin layer of wax, which allows
the rain to wash away the dirt that accumulates on it.
3.6: Importance of Lotus Effect
The importance of the Lotus effect to create self-cleaning materials is clear, so much so that
biologists Neinhuis and Barthlott patented the idea under the name "Lotus-Effect". Since then,
the Lotus Effect has been studied by many botanists and physicists to better understand the
phenomenon and find possible technological applications. Unlike hydrophobicity (water
repulsion), which is a chemical property, super hydrophobicity is a fundamentally physical
property. The lotus effect is attributed to a surface that is covered with needle-shaped wax
tubes, and the remaining surface allows invasion of the water droplet and enlarges the
interaction with water. The difference between both properties depends strongly on the contact
angle between the surface and the water, so that if the contact angle ranges between 90 and 150
degrees, we get hydrophobic properties. On the other hand, with an angle of contact greater
than 150 degrees, this effect is amplified and becomes an impossible to wet surface, thus
obtaining super hydrophobic characteristics.

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Applications of Lotus Effect
The Lotus, an ancestral symbol of spirituality, is now a source of inspiration for innovative
technological applications, potentially applicable in innumerable sectors, including the
building sector, with the creation of roofs and paints capable of self-cleaning.
Some interesting applications of the Lotus effect could be the development of paints that
prevent corrosion of metallic materials. Such paints have excellent physical and structural
properties and the incomparable Lotus-Effect technology. This technology has the ability to
clean itself: the dirt slips away with the rain and the facade remains clean and dry for a long
time.
Another example of the biotechnology applied to this effect is the Rain Stop: a Nano
technological hydrophobic solution for glass and windshields. Once applied, the product
guarantees optimal visibility in all weather conditions, contributing to road safety.
Lotus Effect proposes Nanotechnology products with molecular activity and solutions with
high technological value in the field of protection, cleaning and maintenance of internal and
external supports such as glass, stainless steel, ceramic, wood, fabric and also bricks, tiles,
stone, cement as well as degreasers and lubricants for bicycles, motorcycles and cars and also
professional technical cloths.
Thus, the lotus effect is a particular capacity for self-cleaning, due to the high repellency of the
materials for water, as is the case with the leaves of the flower plant. The study that was done
on the lotus leaf inspired researchers and led to the design and production of useful substances
in different technological applications, from the transport sector to the biomedical one.
Naturally we try to reproduce the lotus effect in paints, tiles, fabrics, floors and other surfaces.
In conclusion, we will have to look more closely at what we have around us and let ourselves
be inspired.

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Plant burrs:
In traditional medicine, the fruits, seeds, roots, and leaves the Burdock plant have long been
used in tinctures, salves, and teas used to treat a wide range of ailments– including colds,
catarrh, gout, rheumatism, stomach ailments, and more. As a relative of wild thistle with
known anti-inflammatory properties, Burdock has also been used as a diuretic, a diaphoretic, a
laxative, and– in some cases– even an aphrodisiac.

In 1941 a Swiss engineer named George de Mestral was hunting in the Jura mountains in
Switzerland when he noticed small burrs from what was later identified as the Burdock plant
stuck to his pant legs and covering his dog‘s fur.
He and his dog had been traversing riverbanks where Burdock typically grows wild (it does
well in disturbed habitats where it can self-seed, and propagates its seeds through burrs that get
stuck and distributed by the fur of passing animals). De Mestral wondered how the tiny hooks
of the cockle-burs (the seed packets produced by Burdock, which are covered with stiff spines)
were sticking to him.
He took the specimen home and examined the tiny hooks at the ends of the burr‘s projections
under a microscope, and he observed an interlocking mechanism that inspired him to consider:
could a series of small-scale, interlocking hooks have a practical application in attire?
The burrs, after all, had clung to de Mestral‘s pant leg in a manner that seemed to defy gravity–
and they persisted even after his dog rolled around in the grass. De Mestral was inspired to
model the configuration for use in clothing.
In 1948, de Mestral patented his idea and, along with help from friends in the weaving
business, finally duplicated the hook and loop fastener inspired by the Burdock plant. The
result of his new invention was Velcro ® brand fasteners, a name that came from the French
words for velvet (―velours‖) and hook (―crochet‖).

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The ensuing product festooned thousands of tiny plastic loops to the exterior wall of a piece of
fabric, which could be snag-fastened to the thousands of tiny hooks attached to a second piece
of cloth whose loops were oriented in the opposite direction. Nylon, when sewn under infrared
light, forms tough hooks for the burr side of the fastener. This is what happens on a
microscopic level when Burdock burrs (and their tiny hooks) get stuck on woven clothing
(which is a series of tiny thread loops).

Fig 4.10: Microscopic view of burr

Velcro:
The word ―Velcro‖ is derived from the French ―velour‖ (velvet) and ―crochet‖ (hooks),So
essentially ―hooked velvet‖. Velcro received a huge boost in popularity after being used by
NASA on parts of astronaut‘s space suits as well as used to allow astronaut‘s to store things
along the walls of their space craft. Because of this, similar to Tang, it is a common
misconception that Velcro was invented by or for NASA.
The company de Mestral started to sell his hook and loop fastener through, Velcro, has
forbidden its employees to use the term ―Velcro‖ due to the fact that their brand has become a
generalized trademark, like Xerox or ―Philips‖ screwdrivers. The employees are instead
instructed to call their product a ―hook and loop fastener‖; ―hook tape‖; or ―loop tape‖. de
Mestral‘s patent for Velcro expire in 1978, after he was unsuccessful in updating it.
Velcro hooks were later found to be able to be significantly strengthened by adding polyester

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to the nylon filaments. A two inch square piece of modern Velcro is strong enough to hang 175
pounds from. During the first ever human artificial heart transplant, Velcro was used to hold
together the heart during surgery. The Velcro used by NASA today is made with Teflon loops,
polyester hooks, and has a glass backing. They even use it in the astronaut‘s helmets where a
small strip functions as a nose scratcher. The U.S. army uses a near silent version of Velcro on
their soldier‘s uniforms. The version they use reduces the ripping noise by about 95% over
traditional Velcro.

Shark skin:
The science behind shark skin speed is fairly simple; when an object is moving under water,
water flowing at the surface of the object moves more slowly than water moving away from
that said object. On smooth surfaces, this contrast of water speed surrounding the object causes
the fast-moving water to break up in to many turbulent vorticles, which slows down the overall
speed of an object moving underwater. Shark skin reduces this speed discrepancy, which in
turn reduces turbulence and allows greater speed.
Under a microscope, shark skin is composed of many tiny, overlapping scales called dermal
denticles of little skin teeth. Each dermal denticle has microscopic grooves running along it
longitudinally, in alignment with water flow when the shark swims forward. These little
grooves speed up slower water by pulling faster water around the shark onto the sharks skin
and mixes it with the slower water, bringing up the average speed of water on the sharks skin.
Denticles also channel the flow of water and cut up sheets of water travelling over a sharks
skin and breaking it up into smaller, less turbulent vorticles. Ultimately, the dermal denticles
on shark skin averages out the speed of water surrounding it, causing less turbulence, so that
the shark can glide through water at a greater overall speed.

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Fig 4.11: Dermal dentcles
Applications: The study of shark skin and its unique composition has led to many scientific
breakthroughs. Most of which are categorized into advancements in transportation, medical
strategy and apparel design.

Transportation:
Yvonne Wilke, Volkmar Stenzel, and Manfred Peschka, scientists from the fraunhofer
Institute, a German research organization, developed a type of paint inspired by studying the
dermal denticles of shark skin that goes on as the outermost coating of airplanes, adding no
weight. The special shark skin paint coats can save up to 4.48 million tons of fuel per year.
Same paint is also used in ship construction, and used for coating for cars.

Medical field:
Because of rough texture, shark skin discourages parasitic growth like algae and barnacles.
Shark skin-inspired surfaces prevent bacteria and microorganisms from holding on to them for
long periods, ultimately resisting bacteria growth. Sharklet Technologies, a biotech startup that

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specializes in making germ-deflecting surfaces, has created a plastic sheet that can adhere to
hospital walls in order to prevent dangerous bacteria from reaching ill patients since it cannot
stick to or spread via the covered walls. One test in a California hospital proved that for three
weeks, Sharklet‘s plastic sheeting surface prevented microorganisms like E. coli and
Staphylococcus A from establishing colonies that were large enough to infect humans. The
plastic surface can cut bacteria by up to 99.99%, ultimately saving thousands of lives.

Fashion: It is typically made with acetate and rayon yarns, as well as with worsted wool and
various synthetic blends. The combination of the color of the yarns and the weaving pattern in
which the colored threads run diagonally to the white yarns results in the finish for which
sharkskin fabric is known. It has a smooth but crisp texture and a two-tone lustrous appearance.
Lightweight and wrinkle-free, sharkskin is ideal for curtains, tablecloths, and napkins.
Sharkskin fabric is popular for both men‘s and women‘s worsted suits, light winter jackets, and
coats. Sharkskin is commonly used as a liner in diving suits and wetsuits.
Shark skin inspired swimsuit called Speedo’s sharkskin swimsuits was developed and used in
the 2008 summer Olympics. However, According to Launder (Professor of Ichthyology), shark
skin only reduces drag when attached to a flexible surface. Human bodies are much less than
those of sharks, so a sharkskin swimsuit does not benefit a human swimmer in terms of drag
reduction.
Kingfisher beak:
The kingfishers have long, dagger-like bills. The bill is usually longer and more compressed in
species that hunt fish, and shorter and broader in species.
Relationship with humans:
Kingfishers are generally shy birds, but despite this, they feature heavily in human culture,
generally due to the large head supporting its powerful mouth, their bright plumage, or some
species' interesting behavior.
The beak that inspired a bullet train:
The method kingfishers use to catch fish seems simple enough. Once a kingfisher spies a fish

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(using special glare-reducing cells in its eyes), it leaves a perch and pluges into the water to
grab it in its beak. Fish; however have a defensive strategy that is hard to overcome.
Specialized receptors along a fish‘s body known as a lateral line, sense disturbances in the flow
of surrounding water. Any suddon movement of water such as a compression wave from a
diving bird and fish are gone with a flick of the tail.So how does a kingfisher hitting the water
surface at over 36 feet/sec, manage to grab a fish in its beak before the fish detects it and flees?

Fig 4.12: The narrow and elongated beak of the kingfisher

The Strategy:
The secret is in the shape of the kingfisher‘s beak. A long and narrow cone, the kingfisher‘s
beak parts and enters the water without creating a compression wave below the surface or a noisy
splash above. The fine point of the conical beak presents little surface area or resistance to the
water upon entry, and the evenly and gradually enlarging cross-section of the beak keeps fluid
flowing smoothly around it as it penetrates further into the water column. This buys the bird
crucial milliseconds to reach the fish before the fish knows to flee. The length of the beak is
critical here: the longer it is, the more gradually the angle of the wedge expands. A shorter,
fatter, or rounder beak would increase the wedge angle, resulting in a splash, a compression
wave, and a fleeing fish.

The Potential:
Eiji Nakatsu, the chief engineer of the company operating Japan‘s fastest trains, wondered if
the kingfisher‘s beak might serve as a model for how to redesign trains not to create such a

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thunderous noise when leaving tunnels and breaking through the barrier of tunnel air and
outside-air. Sure enough, as his team tested different shapes for the front of the new train, the
train became quieter and more efficient as the geometry of its nose became more like the shape
of a kingfisher‘s beak, requiring 15% less energy while traveling even faster than before.

Human blood substitutes:
In blood, the primary role of red blood cells (RBCs) is to transport oxygen via highly regulated
mechanisms involving hemoglobin (Hb). Hb is a tetrameric porphyrin protein comprising of
two α- and two β-polypeptide chains, each containing an iron-containing heme group capable
of binding one oxygen molecule. In military as well as civilian traumatic exsanguinating
hemorrhage, rapid loss of RBCs can lead to suboptimal tissue oxygenation and subsequent
morbidity and mortality. In such cases, transfusion of whole blood or RBCs can significantly
improve survival. However, blood products including RBCs present issues of limited
availability and portability, need for type matching, pathogenic contamination risks, and short
shelf-life, causing substantial logistical. While robust research is being directed to resolve these
issues, parallel research efforts have emerged toward bioengineering of semisynthetic and
synthetic surrogates of RBCs, using various cross-linked, polymeric, and encapsulated forms
of Hb. These Hb-based oxygen carriers (HBOCs) can potentially provide therapeutic
oxygenation when blood or RBCs are not available. Several of these HBOCs have undergone
rigorous preclinical and clinical evaluation, but have not yet received clinical approval in the
USA for human use. While these designs are being optimized for clinical translations, several
new HBOC designs and molecules have been reported in recent years, with unique properties.

Hemoglobin-based oxygen carriers (HBOCs) AND Perflourocarbons (PFC):
The two major types of blood substitutes are volume expanders, which include solutions such
as saline that are used to replace lost plasma volume, and oxygen therapeutics, which are
agents designed to replace oxygen normally carried by the hemoglobin in red blood cells. Of
these two types of blood substitutes, the development of oxygen therapeutics has been the most

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challenging. One of the first groups of agents developed and tested were Perflourocarbons,
which effectively transport and deliver oxygen to tissues but cause complex side effects,
including flu like reactions, and are not metabolized by the body.

Other oxygen therapeutics include agents called hemoglobin-based oxygen carriers (HBOCs),
which are made by genetically or chemically engineering hemoglobin isolated from the red
blood cells of humans or bovines. HBOCs do not require refrigeration, are compatible with all
blood types, and efficiently distribute oxygen to tissues. A primary concern associated with
these agents is their potential to cause severe immune reactions.

Pharmaceutical companies attempted to develop HBOCs (also called oxygen therapeutics)
and PFCs starting in the 1980s and at first, seemed to have some success. However, the results of
most human clinical trials have been disappointing. A study published in 2008 in the Journal
of the American Medical Association summarized the results of 16 clinical trials on five
different blood substitutes administered to 3,500 patients.

Several chemically or genetically engineered hemoglobin-based oxygen carriers (HBOCs)
have been developed with diverse oxygen-binding properties, circulatory half-lives, and
oncotic properties. The purpose of these chemical/genetic alterations was to primarily serve
two functions: first, to stabilize the hemoglobin (Hb) molecule (which dimerizes readily in
dilute solutions) in tetrameric or polymeric form, and second, to improve Hb oxygen carrying
capabilities. However, no allowance in the design of these products has been made to
compensate for the red blood cells (RBCs) own protective mechanisms that prevent Hb
dimerization and heme iron oxidation. RBCs contain highly concentrated Hb (stabilized in the
tetrameric form) of and highly efficient enzymatic machinery that maintains Hb in the
functionally active ferrous form. Oxygen affinity, as reflected by P50 values (when Hb is half-
saturated with oxygen), varies among engineered HBOCs, ranging from as low as P50 of 4.0
mmHg to as high as 40 mmHg.

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Potential adverse effects caused by HBOCs:
HBOCs induced vasoconstriction and pro-coagulant activity, likely associated to NO
scavenging. Oxidative damages due to an increased quantity of free radicals, associated to
haeme iron oxidation.
Neurotoxicity. Cytokine release, vasculitis and thromobosis due to macrophage activation.
Those receiving blood substitutes had a threefold increase in the risk of heart attacks compared
with the control group given human donor blood. Several adverse effects like transient
hypertension, gastrointestinal, pancreatic/liver enzyme elevation and cardiac/renal injury are
reported in humans.

PFCs:
PFCs remain in the bloodstream for about 48 hours. Because of their oxygen-dissolving ability,
PFCs were the first group of artificial blood products studied by scientists. They are first-
generation blood substitutes. Unlike the red-colored HBOCs, PFCs are usually white.
However, since they do not mix with blood they must be emulsified before they can be given
to patients. PFCs are such good oxygen carriers that researchers are now trying to find out if
they can reduce swollen brain tissue in traumatic brain injury. PFC particles may cause flu-like
symptoms in some patients when they exhale these compounds.