Industrial Nanotechnology

18NTO408T - Industrial Nanotechnology
MODULE- I
Description of Topics
Nano electrical and electronic devices: advantages - Data storage
and memory - Micro and nanoelectromechanical systems - Lasers,
lighting and displays – Batteries - Fuel cells - Photovoltaic cells -
Electric double layer capacitors - Nanoparticle coatings for
electrical products
Introduction
Over the past few years, a little word with big potential has been rapidly insinuating itself
into the world's consciousness. That word is "nano." It has conjured up speculation about a
seismic shift in almost every aspect of science and engineering with implications for ethics,
economics, international relations, day-to-day life, and even humanity's conception of its place in
the universe. Visionaries tout it as the panacea for all our woes. Alarmists see it as the next step
in biological and chemical warfare or, in extreme cases, as the opportunity for people to create
the species that will ultimately replace humanity.
When Neil Armstrong stepped onto the moon, he called it a small step for man and a
giant leap for mankind. Nano may represent another giant leap for mankind, but with a step so
small that it makes Neil Armstrong look the size of a solar system. The prefix "nano" means one
billionth. One nanometer (abbreviated as 1 nm) is 1/1,000,000,000 of a meter, which is close to
1/1,000,000,000 of a yard. To get a sense of the nano scale, a human hair measures 50,000
nanometers across, a bacterial cell measures a few hundred nanometers across, and the smallest
features that are commonly etched on a commercial microchip as of February 2002 are around
130 nanometers across. The smallest things seeable with the unaided human eye are 10,000
nanometers across. Just ten hydrogen atoms in a line make up one nanometer.
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Miniaturization of Nano Electrical and Electronic Devices
At present, development in electronic devices means a race for a constant decrease in the
order of dimension. The general public is well aware of the fact that we live in the age of
microelectronics, an expression which is derived from the size (1 μm) of a device‟s active zone,
e.g., the channel length of a field effect transistor or the thickness of a gate dielectric. However,
there are convincing indications that we are entering another era, namely the age of
nanotechnology. The expression “nanotechnology” is again derived from the typical geometrical
dimension of an electronic device, which is the nanometer and which is one billionth (10-9
) of a
meter. 30,000 nm are approximately equal to the thickness of a human hair.
Moore’s Law
Fundamental Concepts In 1965 Gordon Moore observed that silicon transistors were
undergoing a continual process of scaling downward, an observation which was later codified as
Moore's law. Since his observation transistor minimum feature sizes have decreased from 10
micrometers to the 28-22 nm range in 2011. The field of nanoelectronics aims to enable the
continued realization of this law by using new methods and materials to build electronic devices
with feature sizes on the nanoscale. The volume of an object decreases as the third power of its
linear dimensions, but the surface area only decreases as its second power. This somewhat subtle
and unavoidable principle has huge ramifications.
From the industrial point of view, it is of great interest to know which geometrical
dimension can be expected in a given year, but the answer does not only concern manufacturers
of process equipment. In reality, these dimensions affect almost all electrical parameters like
amplification, transconductance, frequency limits, power consumption, leakage currents, etc. In
fact, these data have a great effect even on the consumer. At first glance, this appears to be an
impossible prediction of the future. However, when collecting these data from the past and
extrapolating them into the future we find a dependency as shown in Figure. This observation
was first made by Moore in 1965, and is hence known as Moore‟s law.
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Fig. Moore’s law (Reference book: Nanotechnology and Nanoelectronics Materials,
Devices, Measurement Techniques by W. R. Fahrner)
Nano electrical and electronic devices: advantages
There are several advantages of nanotechnology in electronics and electrical goods that
do give rise directly to environmental and human health concerns. This is the use of synthetically
produced nanoparticles in „nanomaterials‟ to make electronic components or surface coatings
for electrical goods. Nanomaterials are commonly defined as materials designed and produced to
have structural features with at least one dimension of 100 nanometers or less. In electronics, a
number of different nanomaterials are already being used commercially or are being used for
research and development purposes. Some of the most commonly used nanomaterials for
electronic and electrical equipment are carbon nanotubes and quantum dots and, in the case of
surface coatings, nanoparticles of silver.
Some of the existing or emerging uses of nanomaterials in electronics include:
➢
the use of carbon nanotubes in semiconductor chips.
➢
research into the use of a variety of nanomaterials in lighting technologies (light emitting
diodes or LEDs and organic light emitting diodes or OLEDs), with commercial use
expected in the near future.
➢
use of „quantum dots‟ in lasers, along with ongoing research into application of
other nanomaterials in laser technology.
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➢
a variety of nanomaterials used in lithium-ion batteries, or which are being researched
for this use.
➢
potential use of carbon nanotubes and other nanomaterials in fuel cells and by the solar
industry for use in photovoltaics.
➢
research into use of nanomaterials to produce lead-free solder, as well as
the development of solder-free assembly technology.
➢
In addition to the use of nanomaterials in electronics, some nanomaterials are also being
used as surface coatings in certain electrical goods, primarily because they have anti-
microbial properties. Products already marketed as having „anti-microbial‟ nanomaterial
coatings include refrigerators, vacuum cleaners, washing machines, mobile phones and
computer mice.
Data storage and memory
Electronic memory designs in the past have largely relied on the formation of transistors.
However, researches into crossbar switch based electronics have offered an alternative using
reconfigurable interconnections between vertical and horizontal wiring arrays to create ultra high
density memories. An example of such novel devices is based on spintronics. The dependence of
the resistance of a material (due to the spin of the electrons) on an external field is called
magnetoresistance. This effect can be significantly amplified (GMR - Giant Magneto-
Resistance) for nano sized objects, for example when two ferromagnetic layers are separated by
a nonmagnetic layer, which is several nanometers thick (e.g. Co-Cu-Co). The GMR effect has
led to a strong increase in the data storage density of hard disks and made the gigabyte range
possible. The so-called tunneling magnetoresistance (TMR) is very similar to GMR and based on
the spin dependent tunneling of electrons through adjacent ferromagnetic layers. Both GMR and
TMR effects can be used to create a non-volatile main memory for computers, such as the so-
called magnetic random access memory or MRAM.
Nano-RAM
Nano-RAM is a proprietary computer memory technology from the company Nantero. It
is a type of nonvolatile random access memory based on the position of carbon nanotubes
deposited on a chip-like substrate. In theory, the small size of the nanotubes allows for very high
density memories. Nantero also refers to it as NRAM.
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The NRAM acts as a resistive non-volatile random access memory (RAM) and can be
placed in two or more resistive modes depending on the resistive state of the CNT fabric. When
the CNTs are not in contact the resistance state of the fabric is high and represents an "off" or "0"
state. When the CNTs are brought into contact, the resistance state of the fabric is low and
represents an "on" or "1" state. NRAM acts as a memory because the two resistive states are very
stable. In the 0 state, the CNTs (or a portion of them) are not in contact and remain in a separated
state due to the stiffness of the CNTs resulting in a high resistance or low current measurement
state between the top and bottom electrodes. In the 1 state, the CNTs (or a portion of them) are in
contact and remain contacted due to Vander Waals forces between the CNTs, resulting in a low
resistance or high current measurement state between the top and bottom electrodes.
To switch the NRAM between states, a small voltage greater than the read voltage is
applied between top and bottom electrodes. If the NRAM is in the 0 state, the voltage applied
will cause an electrostatic attraction between the CNTs close each other causing a SET
operation. After the applied voltage is removed, the CNTs remain in a 1 or low resistance state
due to physical adhesion (Van der Waals force) with activation energy (Ea) of approximately
5eV. If the NRAM cell is in the 1 state, applying a voltage greater than the read voltage will
generate CNT phonon excitations with sufficient energy to separate the CNT junctions. This is
the phonon driven RESET operation. The CNTs remain in the OFF or high resistance state due
to the high mechanical stiffness (Young's Modulus 1 TPa) with an activation energy much
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greater than 5 eV. Figure 2 illustrates both states of an individual pair of CNTs involved in the
switch operation. Due to the high activation energy (> 5eV) required for switching between
states, the NRAM switch resists outside interference like radiation and operating temperature
that can erase or flip conventional memories like DRAM.
Resistive memory cells (ReRAM)
Resistive memory cells (ReRAM) are regarded as a promising solution for future
generations of computer memories. They will dramatically reduce the energy consumption of
modern IT systems while significantly increasing their performance. Unlike the building blocks
of conventional hard disk drives and memories, these novel memory cells are not purely passive
components but must be regarded as tiny batteries.
Figure 2: Carbon nanotube contact points
Conventional data memory works on the basis of electrons that are moved around and
stored. However, even by atomic standards, electrons are extremely small. It is very difficult to
control them, for example by means of relatively thick insulator walls, so that information will
not be lost over time. This does not only limit storage density, it also costs a great deal of energy.
For this reason, the nanoelectronic components that make use of ions, i.e. charged atoms, for
storing data. Ions are some thousands of times heavier that electrons and are therefore much
easier to 'hold down'. In this way, the individual storage elements can almost be reduced to
atomic dimensions, which enormously improve the storage density. In resistive switching
memory cells (ReRAMs), ions behave on the nanometre scale in a similar manner to a battery.
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The cells have two electrodes, for example made of silver and platinum, at which the ions
dissolve and then precipitate again. This changes the electrical resistance, which can be exploited
for data storage. Furthermore, the reduction and oxidation processes also have another effect.
They generate electric voltage. ReRAM cells are therefore not purely passive systems – they are
also active electrochemical components (Figure 3). Consequently, they can be regarded as tiny
batteries whose properties provide the key to the correct modelling and development of future
data storage.
Figure 3: Configuration of a resistive storage cell (ReRAM) (An electric voltage is built up
between the two electrodes so that the storage cells can be regarded as tiny batteries.
Filaments formed by deposits during operation may modify the battery's properties).
Beyond these are several exploratory storage media:
• MRAM: a nonvolatile storage in which a transistor accesses a stack of magnetic
materials. The conductivity of the stack is changed by the parallel or anti-parallel alignment of
magnetic domains in adjacent layers. MRAMs have been demonstrated with a capacity of 4 Mb.
(1 transistor and 1 resistor/bit)
• Ferromagnetic FET: A magnetic semiconductor affects the conduction of electrons due
to spin effects. Individual devices have been demonstrated at low temperature. (1 transistor/bit)
• Phase Change Memory: Resistance of a chalcopyrite material is programmed through
temperature, with access through a transistor. (1 transistor and 1 resistor/bit)
• Macromolecular Memory: Electrical resistance of a molecular material is programmed
and read through a transistor. (1 transistor and 1 resistor/bit).
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Single Molecule Memory: Electrical resistance of a single molecule is programmed and
read through a transistor. (1 transistor and 1 resistor/bit).
• Nanodots and Defects: Charge is stored on a nanoscale assembly of atoms and defects.
The amount of stored charge changes the conduction of a transistor. (1 transistor/bit)
• Volume Holographic Storage: Information is stored as a modulation in the refractive
index of an optical medium, and accessed through sensitive optical detection.
• Spectral Hole-Burning and/or Spectral Holography: Optical saturation of select
frequency components of an inhomogeneously broadened absorption line indicates the state of
each bit of information. Lasers are used to sense or change the saturation state.
Micro and nanoelectromechanical systems
Microelectromechanical systems
Microelectromechanical systems (MEMS, also written as micro-electro-
mechanical, MicroElectroMechanical or microelectronic and microelectromechanical systems
and the related micromechatronics) is the technology of microscopic devices, particularly those
with moving parts. It merges at the nano-scale into nanoelectromechanical systems (NEMS) and
nanotechnology. MEMS are also referred to as micromachines in Japan, or micro systems
technology (MST) in Europe.
MEMS are made up of components between 1 and 100 micrometres in size (i.e. 0.001 to
0.1 mm), and MEMS devices generally range in size from 20 micrometres to a millimetre (i.e.
0.02 to 1.0 mm), although components arranged in arrays (e.g., Digital micromirror devices) can
be more than 1000mm2
. They usually consist of a central unit that processes data (the
microprocessor) and several components that interact with the surroundings such as
microsensors.[1]
Because of the large surface area to volume ratio of MEMS, forces produced by
ambient electromagnetism (e.g., electrostatic charges and magnetic moments), and fluid
dynamics (e.g., surface tension and viscosity) are more important design considerations than
with larger scale mechanical devices. MEMS technology is distinguished from molecular
nanotechnology or molecular electronics in that the latter must also consider surface chemistry.
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Materials for MEMS manufacturing
The fabrication of MEMS evolved from the process technology in semiconductor device
fabrication, i.e. the basic techniques are deposition of material layers, patterning by
photolithography and etching to produce the required shapes.
Silicon
Silicon is the material used to create most integrated circuits used in consumer electronics
in the modern industry. The economies of scale, ready availability of inexpensive high-quality
materials, and ability to incorporate electronic functionality make silicon attractive for a wide
variety of MEMS applications. Silicon also has significant advantages engendered through its
material properties. In single crystal form, silicon is an almost perfect Hookean material,
meaning that when it is flexed there is virtually no hysteresis and hence almost no energy
dissipation. As well as making for highly repeatable motion, this also makes silicon very reliable
as it suffers very little fatigue and can have service lifetimes in the range of billions to trillions of
cycles without breaking.
Polymers
Even though the electronics industry provides an economy of scale for the silicon
industry, crystalline silicon is still a complex and relatively expensive material to produce.
Polymers on the other hand can be produced in huge volumes, with a great variety of material
characteristics. MEMS devices can be made from polymers by processes such as injection
molding, embossing (or) stereo lithography and are especially well suited to microfluidic
applications such as disposable blood testing cartridges.
Metals
Metals can also be used to create MEMS elements. While metals do not have some of the
advantages displayed by silicon in terms of mechanical properties, when used within their
limitations, metals can exhibit very high degrees of reliability. Metals can be deposited by
electroplating, evaporation, and sputtering processes. Commonly used metals include gold,
nickel, aluminium, copper, chromium, titanium, tungsten, platinum, and silver.
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Ceramics
The nitrides of silicon, aluminium and titanium as well as silicon carbide and
other ceramics are increasingly applied in MEMS fabrication due to advantageous combinations
of material properties. AlN crystallizes in the wurtzite structure and thus
shows pyroelectric and piezoelectric properties enabling sensors, for instance, with sensitivity to
normal and shear forces. TiN, on the other hand, exhibits a high electrical conductivity and large
elastic modulus, making it possible to implement electrostatic MEMS actuation schemes with
ultrathin membranes.[7]
Moreover, the high resistance of TiN against biocorrosion qualifies the
material for applications in biogenic environments and in biosensors.
MEMS basic processes
Deposition processes
One of the basic building blocks in MEMS processing is the ability to deposit thin films
of material with a thickness anywhere between a few nanometres to about 100 micrometres.
There are two types of deposition processes, as follows.
Physical deposition
Physical vapor deposition ("PVD") consists of a process in which a material is removed
from a target, and deposited on a surface. Techniques to do this include the process of sputtering,
in which an ion beam liberates atoms from a target, allowing them to move through the
intervening space and deposit on the desired substrate, and evaporation, in which a material is
evaporated from a target using either heat (thermal evaporation) or an electron beam (e-beam
evaporation) in a vacuum system.
Chemical deposition
Chemical deposition techniques include chemical vapor deposition ("CVD"), in which a
stream of source gas reacts on the substrate to grow the material desired. This can be further
divided into categories depending on the details of the technique, for example, LPCVD (Low
Pressure chemical vapor deposition) and PECVD (Plasma-enhanced chemical vapor deposition).
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Oxide films can also be grown by the technique of thermal oxidation, in which the (typically
silicon) wafer is exposed to oxygen and/or steam, to grow a thin surface layer of silicon dioxide.
Patterning
Patterning in MEMS is the transfer of a pattern into a material.
Lithography
Lithography in MEMS context is typically the transfer of a pattern into a photosensitive
material by selective exposure to a radiation source such as light. A photosensitive material is a
material that experiences a change in its physical properties when exposed to a radiation source.
If a photosensitive material is selectively exposed to radiation (e.g. by masking some of the
radiation) the pattern of the radiation on the material is transferred to the material exposed, as the
properties of the exposed and unexposed regions differs. This exposed region can then be
removed or treated providing a mask for the underlying substrate. Photolithography is typically
used with metal or other thin film deposition, wet and dry etching.
MEMS microphones
Basic principle
The application of MEMS (microelectro-mechanical systems) technology to microphones
has led to the development of small microphones with very high performance. MEMS
microphones offer high SNR, low power consumption, good sensitivity, and are available in very
small packages that are fully compatible with surface mount assembly processes. MEMS
microphones exhibit almost no change in performance after reflow soldering and have excellent
temperature characteristics.
Figure 4: Top port and bottom port MEMS microphones
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MEMS microphone acoustic sensors
MEMS microphones use acoustic sensors that are fabricated on semiconductor
production lines using silicon wafers and highly automated processes. Layers of different
materials are deposited on top of a silicon wafer and then the unwanted material is then etched
away, creating a moveable membrane and a fixed backplate over a cavity in the base wafer. The
sensor backplate is a stiff perforated structure that allows air to move easily through it, while the
membrane is a thin solid structure that flexes in response to the change in air pressure caused by
sound waves.
Figure 5: Cross-section diagram of a MEMS microphone sensor
Figure 6:A typical MEMS microphone sensor viewed from above
Changes in air pressure created by sound waves cause the thin membrane to flex while
the thicker backplate remains stationary as the air moves through its perforations. The movement
of the membrane creates a change in the amount of capacitance between the membrane and the
backplate, which is translated into an electrical signal by the ASIC.
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Nanoelectromechanical systems (NEMS)
Nanoelectromechanical systems (NEMS) are a class of devices integrating electrical and
mechanical functionality on the nanoscale. NEMS form the logical next miniaturization step
from so-called microelectromechanical systems, or MEMS devices. NEMS typically integrate
transistor-like nanoelectronics with mechanical actuators, pumps, or motors, and may thereby
form physical, biological, and chemical sensors. The name derives from typical device
dimensions in the nanometer range, leading to low mass, high mechanical resonance frequencies,
potentially large quantum mechanical effects such as zero point motion, and a high surface-to-
volume ratio useful for surface-based sensing mechanisms.
Nanoelectromechanical systems (NEMS) are made of electromechanical devices that
have critical dimensions from hundreds to a few nanometers. By exploring nanoscale effects,
NEMS present interesting and unique characteristics, which deviate greatly from their pre-
decessor microelectromechanical systems (MEMS). For instance, NEMS-based devices can have
fundamental frequencies in microwave range (∼100 GHz) .
General Properties of NEMS:
Mechanical quality factors in the tens of
thousands Low-energy dissipation
Active mass in the femtogram range.
Power consumption in the order of 10
attowatts. Extreme high integration level.
Approaching 10
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elements per square centimeter.
All these distinguished properties of NEMS devices pave the way to applications such as
force sensors, chemical sensors, biological sensors, and ultrahigh- frequency resonators. The
interesting properties of the NEMS devices typically arise from the behavior of the active parts,
which, in most cases, are in the forms of cantilevers or doubly clamped beams with dimensions
at nanometer scale.
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MULTITERMINAL MECHANICAL DEVICES
The attributes of NEMS described in the next section make clear that we should be
envisioning applications for electromechanical devices with response times and operating
frequencies that are as fast as most of today‟s electron devices. Furthermore, multiterminal
electromechanical devices are possible for i.e. two-, three-, four-ports, etc. Transducers provide
input stimuli (i.e. signal forces), and read out a mechanical response (i.e. output displacement).
At additional control terminals, electrical signals either quasi-static can be applied, and
subsequently converted by the control transducers into quasi-static or time-varying forces to
perturb the properties of the mechanical element in a controlled, useful manner. The generic
picture of this scheme is shown in Figure 7. There is an important point to be made regarding the
"orthogonality" attainable between the input, output and (the possibly multiple) control port(s).
Different physical processes of electromechanical transduction available make it conceivable to
achieve highly independent interaction between these ports, i.e. to have each of these strongly
interacting with the mechanical element, but with only weak direct couplings to each other. For
time varying stimuli when frequency conversion is the goal, this orthogonality can be provided
by tuned (narrowband) transducer response to select input and output signals from control (e.g.
pump) signals.
Figure 7. Schematic representation of a three-terminal electromechanical device.
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NEMS Materials:
Carbon Nanotubes
Carbon nanotubes exist as a macromolecule of carbon, analogous to a sheet of graphite
rolled into a cylinder. They were discovered by Sumio Iijima in 1991 and are a subset of the
family of fullerene structures . The properties of the nanotubes depend on the atomic
arrangement (how sheets of graphite are rolled to form a cylinder), their diameter, and their
length. They are light, stiff, flexible, thermally stable, and chemically inert. They have the ability
to be either metallic or semiconducting depending on the “twist” of the tube, which is called
“chirality” or “helicity.” Nanotubes may exist as either single-walled or multiwalled structures.
Multiwalled carbon nanotubes (MWNTs) are simply composed of multiple concentric single-
walled carbon nanotubes (SWNTs). The spacing between the neighboring graphite layers in
MWNTs is ∼0.34 nm. These layers interactwith each other via van der Waals forces.
Fabrication Methods
The fabrication processes of NEMS devices can be categorized according to two
approaches. Top-down approaches, that evolved from manufacturing of MEMS structures, use
submicron lithographic techniques, such as electron-beam lithography, to fabricate structures
from bulk materials, either thin films or bulk substrates. Bottom-up approaches fabricate the
nanoscale devices by sequentially assembling of atoms and molecules as building blocks. Top-
down fabrication is size limited by facts such as the resolution of the electron-beam
lithography,etching-induced roughness, and synthesis constraints in epitaxially grown substrates.
Significant interest has been shown in the integration of nanoscale materials such as carbon
nanotubes and nanowires, fabricated by bottom-up approaches, to build nanodevices. Most of the
nanodevices reported so far in the literature are obtained by “hybrid” approaches, that is,
combination of bottom-up (self assembly) and top-down (lithographic) approaches. One of the
key and most challenging issues of building carbon nanotubes–based or nanowires-based NEMS
is the positioning of nanotubes or nanowires at the desired locations with high accuracy and high
throughput.
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Nanomanipulation
Manipulation of individual carbon nanotubes using piezo-driven manipulators inside
electron microscope chambers is one of the most commonly used methods to build NEMS and
structures for mechanical testing . In general, the manipulation and positioning of nanotubes is
accomplished in the following manner: (1) a source of nanotubes is positioned close to the
manipulator inside the microscope; (2) the manipulator probe is moved close to the nanotubes
under visual surveillance of the microscope monitor until a protruding nanotube is attracted to
the manipulator due to either van der Waals forces or electrostatic forces; (3) the free end of the
attracted nanotube is “spot welded” by the electron-beam-induced deposition (EBID) of
hydrocarbon or metals, like platinum from adequate precursor gases. Figure 8 shows a three-
dimensional nanomanipulator (Klocke Nanotechnik Co.) having the capability of moving in X,
Y,and Z directions with nanometer displacement resolution. The manipulation process of an
individual carbon nanotube is illustrated in Fig. 9(A)–9(C).
Figure 8. Klocke Nanotechnik nanomanipulator possessing nanometer resolution in the x, y, and z
axes.
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Figure 10. SEM images of the manipulation of carbon nanotubes using the three-
dimensional Klocke Nanotechnik nanomanipulator. (A) Manipulator probe is approaching
a protruding nanotube. The sample is dried nanotube solution on top of a TEM copper
grid. (B) Manipulator probe makes contact with the free end of the nanotube and the
nanotube is welded to the probe by EBID of platinum. (C) A single nanotube mounted to
the manipulator probe.
Electrostatic NEMS:
Electron windmill
As figure 11 shows, the nanomotor consists of a double-walled CNT (DWNT) formed
from an achiral outer tube clamped to external gold electrodes and a narrower chiral inner tube.
The central portion of the outer tube is removed using the electrical-breakdown technique to
expose the free-to-rotate, inner tube. The nanodrill also comprises an achiral outer nanotube
attached to a gold electrode but the inner tube is connected to a mercury bath.
Figure 11 : MWNT nanomotor (A) and nanodrill (B).
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Principle
Conventional nanotube nanomotors make use of static forces that include elastic,
electrostatic, friction and van der Waals forces. The electron windmill model makes use of a new
"electron-turbine" drive mechanism that obviates that need for metallic plates and gates that the
above nanoactuators require. When a DC voltage is applied between the electrodes, a "wind" of
electrons is produced from left to right. The incident electron flux in the outer achiral tube
initially possesses zero angular momentum, but acquires a finite angular momentum after
interacting with the inner chiral tube. By Newton's third law, this flux produces a tangential
force (hence a torque) on the inner nanotube causing it to rotate hence giving this model the
name – "electron windmill". For moderate voltages, the tangential force produced by the electron
wind is much greatly exceed the associated frictional forces.
Applications
Some of the main applications of the electron windmill include:
A voltage pulse could cause the inner element to rotate at a calculated angle hence
making the device behave as a switch or a nanoscale memory element.
Modification of the electron windmill to construct a nanofluidic pump by replacing the
electrical contacts with reservoirs of atoms or molecules under the influence of an
applied pressure difference.
Piezoelectric NEMS
Piezoelectric nanogenerator:
A piezoelectric nanogenerator is an energy harvesting device converting the external
kinetic energy into an electrical energy based on the energy conversion by nano-structured
piezoelectric material. Although its definition may include any types of energy harvesting
devices with nano-structure converting the various types of the ambient energy (e.g. solar power
and thermal energy), it is used in most of times to specifically indicate the kinetic energy
harvesting devices utilizing nano-scaled piezoelectric material after its first introduction in 2006.
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Although still in the early stage of the development, it has been regarded as a potential
breakthrough toward the further miniaturization of the conventional energy harvester, possibly
leading the facile integration with the other types of energy harvester converting the different
types of energy and the independent operation of mobile electronic devices with the reduced
concerns for the energy source, consequently.
Working Principle:
The working principle of nanogenerator will be explained for 2 different cases: the force
exerted perpendicular and parallel to the axis of the nanowire. The working principle for the first
case is explained by a vertically grown nanowire subjected to the laterally moving tip. When a
piezoelectric structure is subjected to the external force by the moving tip, the deformation
occurs throughout the structure. The piezoelectric effect will create the electrical field inside the
nanostructure; the stretched part with the positive strain will exhibit the positive electrical
potential, whereas the compressed part with the negative strain will show the negative electrical
potential. This is due to the relative displacement of cations with respect to anions in its
crystalline structure. As a result, the tip of the nanowire will have an electrical potential
distribution on its surface, while the bottom of the nanowire is neutralized since it is grounded.
Figure 12. Piezoelectric nanogenerator
Note: Working principle of nanogenerator where an individual nanowire is subjected to the
force exerted perpendicular to the growing direction of nanowire. (a) An AFT tip is swept
through the tip of the nanowire. Only negatively charged portion will allow the current to
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flow through the interface. (b) The nanowire is integrated with the counter electrode with
AFT tip-like grating. As of (a), the electrons are transported from the compressed portion
of nanowire to the counter electrode because of Schottky contact.
Applications
Nanogenerator is expected to be applied for various applications where the periodic kinetic
energy exists, such as wind and ocean waves in a large scale to the muscle movement by the beat
of a heart or inhalation of lung in a small scale. The further feasible applications are as follows:
➢
Self-powered nano/micro devices. One of the feasible applications of nanogenerator is an
independent or a supplementary energy source to nano/micro devices consuming
relatively low amount of energy in a condition where the kinetic energy is supplied
continuously.
➢
Smart Wearable Systems. The outfit integrated or made of the textiles with the
piezoelectric fiber is one of the feasible applications of the nanogenerator. The kinetic
energy from the human body is converted to the electrical energy through the
piezoelectric fibers, and it can be possibly applied to supply the portable electronic
devices such as health-monitoring system attached with the Smart Wearable Systems.
The nanogenerator such as VING can be also easily integrated in the shoe employing the
walking motion of human body.
Piezoresistive NEMS
CNT Network Bio-Stress Sensors:
A single nanotube experiences a change in electrical resistance when experiencing stress
or strain. This piezoresistive effect changes the current flow through the nanotube, which can be
measured in order to accurately quantify the applied stress. A semi-random positioning of many
overlapping nanotubes forms an electrically conducting network composed of many
piezoresistive nanotubes. If the variance of the tube lengths and angles are known and
controllable during manufacture, an eigensystem approach can be used to determine the expected
current flow between any two points in the network. The tube network is embedded within
orthopedic plates, clamps, and screws and in bone grafts in order to determine the state of bone
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healing by measuring the effect of a load on the plate, clamp, screw, or other fixation device
attached to the bone. A healed bone will bear most of the load while a yet unhealed bone will
defer the load to the fixation device wherein the nanotube network may measure the change in
resistivity. Measurement is done wirelessly by electrical induction. This allows the doctor to
accurately assess patient healing and also allows the patient to know how much stress the
affected area may safely tolerate. Wolff's law indicates that bone responds positively to safe
amounts of stress, which may be necessary for proper healing.
Nanotechnology in Laser Industry
Multiphoton lithography
Multiphoton lithography (also known as direct laser lithography or direct laser writing) of
polymer templates has been known for years by the photonic crystal community. Similar to
standard photolithography techniques, structuring is accomplished by illuminating negative-tone
or positive-tone photoresists via light of a well-defined wavelength. The fundamental difference
is, however, the avoidance of reticles. Instead, two-photon absorption is utilized to induce a
dramatic change in the solubility of the resist for appropriate developers. Hence, multiphoton
lithography is a technique for creating small features in a photosensitive material, without the use
of complex optical systems or photomasks. This method relies on a multi-photon absorption
process in a material that is transparent at the wavelength of the laser used for creating the
pattern. By scanning and properly modulating the laser, a chemical change (usually
polymerization) occurs at the focal spot of the laser and can be controlled to create an arbitrary
three-dimensional periodic or non-periodic pattern. This method has been used for rapid
prototyping of structures with fine features.
Nanotechnology laser printing
Nanotechnology revolutionizes laser printing technology, allowing you to print high-
resolution data and colour images of unprecedented quality and microscopic dimensions. Using
this new technology, we reproduced a colour image of Mona Lisa which is less than one pixel on
an iPhone Retina display. The laser technology allows printing in a mind-blowing resolution of
127,000 DPI. In comparison, weekly or monthly magazines are normally printed in a resolution
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equivalent to 300 DPI. Printing the microscopic images requires a special nanoscale-structured
surface.
The structure consists of rows with small columns with a diameter of merely 100
nanometres each. This structured surface is then covered by 20 nanometres of aluminium. When
a laser pulse is transmitted from nanocolumn to nanocolumn, the nanocolumn is heated locally,
after which it melts and is deformed. The temperature can reach up to 1,500°C, but only for a
few nanoseconds, preventing the extreme heat from spreading. The intensity of the laser beam
determines which colours are printed on the surface, since the extent of column deformation
decides which colour is reflected. Low-intensity laser pulses lead to a minor deformation of the
nanocolumn, resulting in blue and purple colour tone reflections. Strong laser pulses create a
drastic deformation, which gives the reflection from the nanocolumn an orange and yellow
colour tone.
The new laser printing technology can also be used on a larger scale to personify
products such as mobile phones with unique decorations, names, etc. Foreign companies
producing parts for cars, such as instrument panels and buttons, are already taking a keen interest
in the technology as it can simplify the production. Today, the large number of different
instrument panels must be adapted to the various accessories that the car has, including
airconditioning, USB, cigarette lighters,etc.
Figure 13: printing a microscopic Mona Lisa. She is 50 micrometres long or about 10,000
times smaller than the real Mona Lisa in the Louvre in Paris.
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Nanotechnology in Lighting and Displays
Nanotechnology has influenced the lighting industry with respect to innovations in
materials, which improve performance of conductive modules, delivering more efficient devices
and bringing down operational costs. Using nanotechnology in the lighting industry may open
new paths for researchers for example flexible devices such as wearables or large area LED
lighting. In addition, the limitations of silicon materials offer potential opportunities for
nanomaterials. Carbon materials such as nanotubes, nanowires, nanoparticles, and graphene have
been observed as the key nanomaterials that are being explored on a large scale for utilization in
displays and lighting.
The Nanotech TechVision Opportunity Engine (TOE) provides intelligence on
technologies, products, processes, applications, and strategic insights on nanotechnology-related
innovations and their impact across various industries. Technology focus areas include
nanomaterials, nanocoatings, nanohealthcare, nanomedicine, and nanomanufacturing.
Miniaturization, a move toward lower power consumption, and the need for enhanced
features are driving innovations in the electronics sector. Technology focus areas include
semiconductor manufacturing and design, flexible electronics, 3D integration/IC, MEMS and
NEMS, solid state lighting, advanced displays, nanoelectronics, wearable electronics, brain
computer interface, advanced displays, near field communication, and next generation data
storage or memory.
Nanotechnology-based lighting and display systems: organic light-emitting diode (OLED)
Artificial lighting by means of electrical light sources plays a crucial role in everyday
life, both for interior as well as exterior lighting applications. It helps improve the safety, comfort
and performance on roads, in the apartment and at work. According to the International Energy
Agency, nearly 20 percent of conducted electricity worldwide is used for lighting purposes. In
Germany, 15 percent of consumed electricity is used for illumination. Lighting for commercial,
trade and service applications accounts for the lion‟s share (UBA 2009). The demand for
artificial light sources continues to rise, making the development of energy-conserving lighting
solutions especially important.
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Lighting has a major potential when it comes to the conservation of resources and climate
protection. The so-called solid-state emitters are promising in this regard. They help drastically
increase the energy efficiency of lighting. Aside from organic light-emitting diodes (OLEDs), the
development of novel, nanotechnology-based lighting technologies likewise includes OLEDs
combined with quantum dots, quantum dot-enhanced ILEDs or silicon-based ILEDs (SiLEDs).
Which of these lighting technologies will be playing a significant role in the future, and
especially what kinds of impacts they will have on the environment, remains to be seen. The fact
sheet at hand is focusing on the uses of OLEDs for lighting purposes. Their function is based on
nanotechnology-structured organic semiconductor materials. According to experts, this novel
lighting technology will revolutionise both interior and exterior lighting as well as the display
area (TVs, monitors, telephones) in the near future and in part replace existing systems.
Function and structure of an OLED
An OLED is a thin, flat luminous component with a thickness of usually less than 1
micrometre. It consists of at least one light-emitting layer (emitter layer) made of organic
semiconductor material, is generally built with several layers, each with a thickness of up to 100
nanometres (nm ), which are positioned between two electrodes (see Figure 14). One or both
electrodes of the OLED are transparent such that light can radiate toward one or both directions
and gives it a translucent appearance when switched off. Compared to ILEDs, OLEDs have the
advantage that the colour of the light can be customized to reflect the entire visible spectrum.
Figure 14: Schematic representation of the structure of an OLED
24

When switched on, voltage builds up between the electrodes which leads to a drift of the positive
charge (p-holes) and the negative charge (electrons) in the semi-conductor layers toward each
other. The charges accumulate in the emitter layer, creating an excited state when hitting each
other (exciton). Depending on the mechanism, this may be the direct excitation of a dyestuff
molecule (or) the dyestuff is excited by the energy released when the exciton decays. When the
excited state of the dyestuff changes back to the basic state, a light particle (photon) with a
defined wavelength is emitted. Two types of OLEDs are distinguished: the emitter layer consists
of polymers (PLED) or of small organic molecules (small molecular organic LED = SMOLED).
Materials used for OLED lighting
Component Material
Organic semi-
conductor/emitter layer
Cathode
Anode
Other layers, including
electron injection layer, hole
conducting layer
Carrier material/cover
Housing/holder/frame
Electronic components
Polymers (e.g. poly-p-phenylene vinylene, PPV) or molecules
(light emission); triarylamines, triphenylene derivatives, copper
phthalocyanine (hole conductor); tris(8-oxyquinoline)
aluminium complex (electron conductor); partly contained: rare
earth elements (e.g. europium), precious metals (platinum,
iridium)
Metal, e.g.: aluminium, barium, magnesium, calcium, ruthenium,
silver alloys, lithium fluoride
Transparent conductive oxides (TCOs), mainly Indium Tin
Oxide (ITO); alternatives: doped tin oxides, silver nanowire
Lithium fluoride, caesium fluoride or silver; PEDOT/PSS
(poly(3,4-ethylene dioxythiophene/ polystyrene sulfonate,
copper phthalocyanine)
Silicon, glass (e.g. borosilicate glass or normal soda-lime glass),
polymer foil, metal foil (aluminium, stainless steel), flexible
plastic
No detailed information / many possibilities
No detailed information
Batteries:
A lithium-ion battery (sometimes Li-ion battery or LIB) is a member of a family of
rechargeable battery types in which lithium ions move from the negative electrode to the positive
electrode during discharge and back when charging. Li-ion batteries use an intercalated lithium
compound as one electrode material, compared to the metallic lithium used in a non-rechargeable
lithium battery. The electrolyte, which allows for ionic movement, and the two electrodes are the
constituent components of a lithium-ion battery cell.
25

Figure 15. Schematic diagram of lithium-ion battery
1. During charging, lithium ions flow from the positive electrode to the negative electrode
through the electrolyte . Electrons also flow from the positive electrode to the negative electrode,
but take the longer path around the outer circuit. The electrons and ions combine at the negative
electrode and deposit lithium there.
2. When no more ions will flow, the battery is fully charged and ready to use.
3. During discharging, the ions flow back through the electrolyte from the negative electrode to
the positive electrode. Electrons flow from the negative electrode to the positive electrode
through the outer circuit, powering your laptop. When the ions and electrons combine at the
positive electrode, lithium is deposited there.
4. When all the ions have moved back, the battery is fully discharged and needs charging up
again. The three primary functional components of a lithium-ion battery are the positive and
negative electrodes and electrolyte. Generally, the negative electrode of a conventional lithium-
26

ion cell is made from carbon. The positive electrode is a metal oxide, and the electrolyte is a
lithium salt in an organic solvent. The electrochemical roles of the electrodes reverse between
anode and cathode, depending on the direction of current flow through the cell.
Lithium-ion batteries are becoming a common replacement for the lead acid batteries that have
been used historically for golf carts and utility vehicles. Instead of heavy lead plates and acid
electrolyte, the trend is to use lightweight lithium-ion battery packs that can provide the same
voltage as lead-acid batteries, so no modification to the vehicle's drive system is required.
Li-ion cells (as distinct from entire batteries) are available in various shapes, which can generally
be divided into four groups
Small cylindrical (solid body without terminals, such as those used in laptop batteries)
Large cylindrical (solid body with large threaded terminals)
Pouch (soft, flat body, such as those used in cell phones)
Prismatic (semi-hard plastic case with large threaded terminals, such as
vehicles' traction packs)
Advantages
✓
High energy density - potential for higher capacities.
✓
Does not need prolonged priming when new. One regular charge is all that's
needed. ✓
Relatively low self-discharge - self-discharge is less than half that of
nickel-based
batteries.
✓
Low Maintenance - no periodic discharge is needed; there is no memory.
✓
Specialty cells can provide very high current to applications such as power tools.
Limitations
Requires protection circuit to maintain voltage and current within safe limits.
Subject to aging, even if not in use - storage in a cool place at 40% charge reduces
the aging effect.
Transportation restrictions - shipment of larger quantities may be subject to regulatory
control. This restriction does not apply to personal carry-on batteries.
Expensive to manufacture
Not fully mature - metals and chemicals are changing on a continuing basis.
27

Applications:
LEV (Light Electric Vehicles)
EES (Energy Storage Systems)
Storage for solar panels
• Electric vehicles
Marine
Computers and Laptops
Nanomaterial Used Lithium Ion Batteries:
Using nanotechnology in the manufacture of batteries offers the following benefits:
Reducing the possibility of batteries catching fire by providing less flammable
electrode material.
Increasing the available power from a battery and decreasing the time required to
recharge a battery. These benefits are achieved by coating the surface of an electrode with
nanoparticles. This increases the surface area of the electrode thereby allowing more current to
flow between the electrode and the chemicals inside the battery. This technique could increase
the efficiency of hybrid vehicles by significantly reducing the weight of the batteries needed to
provide adequate power.
Increasing the shelf life of a battery by using nanomaterials to separate liquids in the
battery from the solid electrodes when there is no draw on the battery. This separation prevents
the low level discharge that occurs in a conventional battery, which increases the shelf life of the
battery dramatically.
Mechanism of Nano Batteries:
• Shortens the existing distance with in the electrode material.
• Accelerates the recharging and discharging rate.
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Advantages of Nano Batteries
silicon nanoparticles with graphene cages helps the silicon to remain in the graphene cage
without degrading the anode. A lithium ion battery that can recharge within 10 minutes using
silicon nanoparticles in the anode of the battery. The use of silicon nanoparticles, rather than
solid silicon, prevents the cracking of the electrode which occurs in solid silicon electrodes.
catalyst made from nitrogen-doped carbon-nanotubes, instead of platinum can store up to 10
times as much energy as lithium-ion batteries.
Electrodes made from carbon nanotubes grown on graphene with very high surface area and
very low electrical resistance. The graphene was first grewed on a metal substrate then grew
carbon nanotubes on the graphene sheet. Because the base of each nanotube is bonded, atom to
atom, to the graphene sheet the nanotube-graphene structure is essentially one large molecule
with a huge surface area.
Batteries with nanomaterials have four times the storage capacity of current lithium ion
batteries.
Graphene used on the surface of anodes make lithium-ion batteries to recharge about 10 times
faster than conventional Li-ion batteries.
Cathodes made of a nanocomposite designed to increase the energy density of Li-ion batteries.
29

Lithium ion batteries with electrodes made from nano-structured lithium titanate that
significantly improves the charge/discharge capability at sub freezing temperatures as well as
increasing the upper temperature limit at which the battery remains safe from thermal runaway
Fuel Cells:
A fuel cell is a device that converts the chemical energy from a fuel into electricity
through a chemical reaction of positively charged hydrogen ions with oxygen or another
oxidizing agent. Fuel cells operates much like a battery, except they don‟t require electrical
recharging.
Every fuel cell has two electrodes, one positive, called the anode, and one negative,
called the cathode. These are separated by an electrolyte barrier. Fuel goes to the anode side,
while oxygen (or just air) goes to the cathode side. When both of these chemicals hit the
electrolyte barrier, they react, split off their electrons, and create an electric current. A chemical
catalyst speeds up the reactions here.
The most important design features in a fuel cell are
➢
The electrolyte substance. The electrolyte substance usually defines the type of fuel cell.
➢
The fuel that is used. The most common fuel is hydrogen.
➢
The anode catalyst breaks down the fuel into electrons and ions. The anode catalyst is
usually made up of very fine platinum powder.
➢
The cathode catalyst turns the ions into the waste chemicals like water or carbon dioxide.
The cathode catalyst is often made up of nickel but it can also be a nanomaterial-based
catalyst.
A typical fuel cell produces a voltage from 0.6 V to 0.7 V at full rated load. Voltage decreases as
current increases, due to several factors:
➢
Activation loss
➢
Ohmic loss (voltage drop due to resistance of the cell components and interconnections)
➢
Mass transport loss (depletion of reactants at catalyst sites under high loads, causing rapid
loss of voltage)
30

To deliver the desired amount of energy, the fuel cells can be combined in series to yield higher
voltage, and in parallel to allow a higher current to be supplied. Such a design is called a fuel cell
stack. The cell surface area can also be increased, to allow higher current from each cell. Within
the stack, reactant gases must be distributed uniformly over each of the cells to maximize the
power output.
Benefits of fuel cells
✓
Fuel cells have a higher efficiency than diesel or gas engines.
✓
Most fuel cells operate silently, compared to internal combustion
engines. ✓
They are therefore ideally suited for use within buildings such as
hospitals. ✓
Fuel cells can eliminate pollution caused by burning fossil fuels;
for hydrogen
fuelled fuel cells, the only by-product at point of use are water.
✓
If the hydrogen comes from the electrolysis of water driven by
renewable energy, then usingfuel cells eliminates greenhouse gases over the whole cycle.
31

✓
Fuel cells do not need conventional fuels such
as oil or gas and can therefore reduceeconomic
dependence on oil producing countries, creating greater energy security for the user nation.
✓
Since hydrogen can be produced anywhere where there is water and a
source of power, generation of fuel can be distributed and does not have to be grid-dependent.
Applications of fuel cells
Today categorises the use of fuel cells into three broad areas: portable power generation,
stationary power generation, and power for transportation.
Nanotechnology in Fuel Cells
The spacing between platinum nanoparticles affected the catalytic behavior and that by
controlling the packing density of the platinum nanoparticles they could reduce the amount of
platinum needed. The platinum was alloyed with copper and then removed the copper from the
surface of the film, which caused the platinum atoms to move closer to each other (reducing the
lattice space). It turns out that platinum with reduced lattice spacing is more a more effective
catalyst for breaking up oxygen molecules into oxygen ion. The difference is that the reduced
spacing changes the electronic structure of the platinum atoms so that the separated oxygen ions
more easily released, and allowed to react with the hydrogen ions passing through the proton
exchange membrane.
Another way to reduce the use of platinum for catalyst in fuel cell cathodes is being
developed. one nanometer thick layer of platinum and iron was deposited on spherical
nanoparticles of palladium generates 12 times more current than a catalyst using pure platinum,
and lasted ten times longer.
Benefits of Nanomaterials in Fuel Cells
The catalyst is made from a sheet of graphene coated with cobalt nanoparticles. If this
catalyst works out for production use with fuel cells it should be much less expensive than
platinum based catalysts.
A catalyst using platinum-cobalt nanoparticles produces 12 times more catalytic activity
than pure platinum. In order to achieve this performance the researchers annealed the
nanoparticles so they formed a crystalline lattice which reduced the spacing between platinum
atoms on the surface, increasing their reactivity.
32

Proton exchange membrane using a silicon layer with pores of about 5 nanometers in
diameter capped by a layer of porous silica uses in fuel to capture the hydrogen. The silica layer
is designed to insure that water stays in the nanopores. The water combines with the acid
molecules along the wall of the nanopores to form an acidic solution, providing an easy pathway
for hydrogen ions through the membrane. Evaluation of this membrane showed it to have much
better conductivity of hydrogen ions (100 times better conductivity was reported) in low
humidity conditions than the membrane normally used in fuel cells.
Hydrogen has a high bonding energy to carbon, and it is annealed and plasma treatment
was given to increase this bonding energy. Because graphene is only one atom thick it has the
highest surface area exposure of carbon per weight of any material. High hydrogen to carbon
bonding energy and high surface area exposure of carbon gives graphene has a good chance of
storing hydrogen. The researchers found that they could store14% by weight of hydrogen in
graphene.
33

Nanotechnology in Photovoltaic cells
Photovoltaics (PV) is a term which covers the conversion of light into electricity using
semiconducting materials that exhibit the photovoltaic effect, a phenomenon studied in physics,
photochemistry, and electrochemistry. A typical photovoltaic system employs solar panels, each
comprising a number of solar cells, which generate electrical power. PV installations may be
ground-mounted, rooftop mounted or wall mounted. The mount may be fixed, or use a solar
tracker to follow the sun across the sky. Solar PV has specific advantages as an energy source: its
operation generates no pollution and no greenhouse gas emissions once installed, it shows simple
scalability in respect of power needs and silicon has large availability in the Earth‟s crust. PV
systems have the major disadvantage that the power output is dependent on direct sunlight, so
about 10-25% is lost if a tracking system is not used, since the cell will not be directly facing the
sun at all times. Dust, clouds, and other things in the atmosphere also diminish the power output.
Another main issue is the concentration of the production in the hours corresponding to main
insolation, which don't usually match the peaks in demand in human activity cycles. Unless
current societal patterns of consumption and electrical networks mutually adjust to this scenario,
electricity still needs to be made up by other power sources, usually hydrocarbon.
The goals are to enhance understanding of conversion and storage phenomena at the
nanoscale, improve nanoscale characterization of electronic properties, and help enable
economical nonmanufacturing of robust devices. -The initiative has three major thrust areas
– improve photovoltaic solar electricity generation;
– improve solar thermal energy generation and conversion; and
– improve solar-to-fuel conversions.
The thermodynamic limit of 80% efficiency is well beyond the capabilities of current
photovoltaic technologies, whose laboratory performance currently approaches only 43%.
Nanomaterials even make it possible to raise light yield of traditional crystalline silicon solar
cells. By using cheaper, nanoscale materials than the current dominant technology (single-crystal
silicon, which uses a large amount of fossil fuels for production), the cost of solar cells could be
brought down.
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Solar Cells are arranging in large grouping called arrays these arrays consists of large no
of individual cells converts sunlight energy into electrical energy. Examples of semiconductor
materials employed in solar cells include silicon gallium arsenic etc.
Demerits of conventional solar cells
How can nanotechnology improve solar cells
Using nanoparticles in the manufacture of solar cells has the following benefits:
➢
Reduced manufacturing costs as a result of using a low temperature process similar to
printing instead of the high temperature vacuum deposition process typically used to
produce conventional cells made with crystalline semiconductor material.
35

➢
Reduced installation costs achieved by producing flexible rolls instead of rigid crystalline
panels. Cells made from semiconductor thin films will also have this characteristic.
➢
Currently available nanotechnology solar cells are not as efficient as traditional ones,
however their lower cost offsets this. In the long term nanotechnology versions should
both be lower cost and, using quantum dots, should be able to reach higher efficiency
levels than conventional ones.
Types of Solar cells:
To generate electricity from sun there are two main types of solar cells:
1. Single- Crystal Silicon (Traditional):
➢
It is wide spread
➢
It is expensive to manufacture
2. Dye sensitized (Nano)
➢
Newer less proven
➢
Inexpensive to manufacture
➢
Flexible
Solar Cells: Nanotechnology Applications under Development:
A honeycomb like structure of graphene in which the graphene sheets are held apart by
lithium carbonate. They have used this "3D graphene" to replace the platinum in a dye sensitized
solar cell and achieved 7.8 percent conversion of sunlight to electricity. A solar cell that uses a
36

copper indium selenide sulfide quantum dots are non-toxic as well as low cost. Solar cells made
from single molecule thick sheets of graphene and materials such as molybdenum diselenide.
They are predicting that this type of solar cells could produce up to 1000 times as much more
power for a given weigh of material than conventional solar cells. A solar cell using graphene
coated with zinc oxide nanowires will allow the production of low cost flexible solar cells at high
enough efficiency to be competitive.
Aerotaxy method is used to grow semiconducting nanowires on gold nanoparticles. Self-
assembly techniques is used to align the nanowires on a substrate; forming a solar cell or other
electrical devices. The gold nanoparticles replace the silicon substrate on which conventional
semiconductor based solar cells are built.
Combining carbon nanotubes and bucky balls with a polymer solar cells are produced.
While another group of researchers are only using nanotubes and bucky balls. A third research
group is also using nanotubes and buck balls along with graphene to build a solar cell.
Using light absorbing nanowires embedded in a flexible polymer film is another method
being developed to produce low cost flexible solar panels. Using light absorbing graphene sheets
to produce low cost solar panels organic solar cells that are self-repairing. Organic solar cells that
can be applied by spray painting, possibly turning the surface of a car into a solar cell. Solar cells
that can be installed as a coating on windows or other building materials, referred to as "Building
Integrated Photovoltaic's".
Electric double-layer capacitor
Electric double-layer capacitors (EDLC) are electrochemical capacitors which energy
storage predominant is achieved by double-layer capacitance. In the past, all electrochemical
capacitors were called "double-layer capacitors". However, since some years it is known that
double-layer capacitors together with pseudocapacitors are part of a new family of
electrochemical capacitors called supercapacitors, also known as ultracapacitors. Supercapacitors
do not have a conventional solid dielectric.
Principle of Electrical Double Layer Capacitor
Unlike a ceramic capacitor or aluminum electrolytic capacitor, the Electrical Double
Layer Capacitor (EDLC) contains no conventional dielectric. Instead, an electrolyte (solid or
liquid) is filled between two electrodes. In EDLC, an electrical condition called "electrical
37

double layer" which is formed between the electrodes and electrolyte works as the dielectric.
Capacitance is proportional to the surface area of the electrical double layer. Therefore using
activated carbon which has large surface area for electrodes enables EDLC to have high
capacitance.
Principle of Electrical Double Layer Capacitor
The mechanism of ion absorption and desorption to the electrical double layer contributes to
charge and discharge of EDLC. By applying voltage to the facing electrodes, ions are drawn to
the surface of the electrical double layer and EDLC is charged. Conversely, they move away
when discharging EDLC. This is how EDLC is charged and discharged.
Charge and Discharge of EDLC
38

Structure of EDLC
EDLC consists of electrodes, electrolyte (and electrolyte salt) , and the separator, which
prevents facing electrodes from contacting each other. Activated carbon powder is applied to the
electricity collector of the electrodes. The electrical double layer is formed on the surface where
each powder connects with an electrolyte.
Structure of EDLC
Activated carbon electrodes consist of a various amount of powder with holes on their respective
surfaces. The electrical double layer is formed on the surface where each powder contacts with
the electrolyte.
Electrode Structure
Nanotechnology in Electric double-layer capacitor
Nanoflowers Improve Ultracapacitors
A capacitor consists of two electrodes with opposite charges, often separated by an
insulator that keeps electrons from jumping directly between them. The researchers have
39

developed an electrode that can store twice as much charge as the activated-carbon electrodes
used in current ultracapacitors. The new electrode contains flower-shaped manganese oxide
nanoparticles deposited on vertically grown carbon nanotubes.
Nanoflower power: A transmission electron microscope image shows a flowerlike
manganese oxide nanoparticle deposited at the junction of crossed carbon nanotubes.
Used as an electrode material, this nanotube-manganese-oxide composite could
improve the energy-storage ability of ultracapacitors, which show promise as powerful,
long-lasting replacements for batteries.
The electrodes deliver five times as much power as activated-carbon electrodes. The
electrode‟s longevity also compares with that of activated-carbon electrodes. In a typical
ultracapacitor, two aluminum electrodes are suspended in an electrolyte. A voltage applied to the
electrodes separates the positive and negative ions in the electrolyte, which get attracted to the
oppositely charged electrodes. How much energy the ultracapacitor can store largely depends on
the electrodes‟ surface area: the more area, the more space to store charge. Coating the
electrodes with activated carbon increases their surface area, since a teaspoonful of the porous,
spongelike material has about the surface area of a football field. Ultracapacitors can store
millions of times more energy than the tiny capacitors used in electronic circuits. But their
performance still pales beside that of batteries, which store energy using chemical reactions.
Nanoparticle coatings for electrical products
Nanomaterials are being applied in more and more fields within engineering and
technology. One of the key benefits of nanomaterials is that their properties differ from bulk
material of the same composition. The properties of nanoparticles, for example, can be easily
40

altered by varying their size, shape, and chemical environment. Copper is found to be too soft for
some applications, and hence it is often combined with other metals to form numerous alloys
such as brass, which is a copper-zinc alloy. Copper nanoparticles are graded as highly flammable
solids, therefore they must be stored away from sources of ignition. They are also known to be
very toxic to aquatic life.
Copper Nanoparticle Applications in Eelectrical Conductivity:
Copper Nanoparticle Applications have great interest due to their optical, catalytic,
mechanical and electrical properties. Copper is a good alternative material for noble metals such
as Au and Ag as it is highly conductive and much more economical than them. Copper plays an
important role in electronic circuits because of its excellent electrical conductivity. Copper
Nanoparticle Applications are inexpensive and their properties can be controlled depending on
the synthesis method. Also in catalyst, the nanoparticles have a higher efficiency than particles.
Copper Nanoparticle Applications are synthesized through different techniques. The most
important methods for the synthesis of copper nanoparticles are chemical methods such as
chemical reduction, electrochemical techniques, photochemical reduction and thermal
decomposition. Copper nanoparticles can easily oxidize to form copper oxide.
Nanoparticle-coating makes coaxial cables lighter
Common coaxial cables could be made 50 percent lighter with a new nanotube-based
outer conductor developed by Rice University scientists. A coating that could replace the tin-
coated copper braid that transmits the signal and shields the cable from electromagnetic
interference. The metal braid is the heaviest component in modern coaxial data cables. Replacing
the outer conductor with flexible, high-performance coating would benefit airplanes and
spacecraft, in which the weight and strength of data-carrying cables are significant factors in
performance. Current coaxial cables have to use a thick metal braid to meet the mechanical
requirements and appropriate conductance.
Coaxial cables consist of four elements: a conductive copper core, an electrically
insulating polymer sheath, an outer conductor and a polymer jacket. The Rice lab replaced only
the outer conductor by coating sheathed cores with a solution of carbon nanotubes in
chlorosulfonic acid. Compared with other attempts to use carbon nanotubes in cables, this
41

method yields a more uniform conductor and has higher throughput. Replacing the braided metal
conductor with the nanotube coating eliminated 97 percent of the component's mass.
Figure: Replacing the braided outer conductor in coaxial data cables with a coat of
conductive carbon nanotubes saves significant weight
Reducing energy usage with nanoparticle-coatings
Thermochromic nano-coatings employed appropriately can help reduce energy usage and
generate savings. The coatings either absorb heat or permit its reflection, depending on their
temperature. The special properties of nano-composites only become apparent if the particles do
not clump so that an agglomeration is avoided. There is a possibility of developement a process
through which the nanoparticles are distributed uniformly in the polymer matrix. In addition,
integrating the nanoparticles in the plastic system provides extra safety. The binding forces
prevent the uncontrolled release of individual nanoparticles.
42

The process is highly adaptable and suited to processing quite varied nanomaterials. Additional
advantages are small amounts of substances can be bound in environmentally-friendly, water-
based systems of plastics that release hardly any volatile organic compounds. These coatings can
be applied directly without first requiring a primer coat. In addition, the layers prevent oxygen
from reaching the metal and thereby protect against corrosion.
Reduced energy usage through color change
The thermochromic coatings change color depending on their temperature. The coatings
thereby either absorb heat or become transparent and permit its reflection. Metal strip possesses
very special properties when coated in this way. If temperatures are below 30 °Celsius (about 86
°F), the black coating absorbs heat. If it is warmer, the color changes. The varnish, which has
now become transparent, allows the infrared radiation to be reflected. Strip and wire coated like
this are useful in architectural applications. They can be interwoven and used as exterior self-
regulating thermal cladding for walls and façades to help cool buildings passively and thereby
reduce operating costs. The researchers are continuing to work on additional nano-systems such
as coatings with luminescent properties, for instance.
Figure: Metal strip coated with thermochromic nanoparticles. At temperatures above 30°
Celsius (about 86 °F), the coating is transparent and the metal underneath reflects heat.
These kinds of effects are useful for safety markings and signage. The coatings can also
help clearly differentiate branded products from pirated copies, since pirates do not have these
kinds of luminescent nano-coatings at their disposal.
43

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