Nanotechnology in Mechanical Engineering

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Nanotechnology in Mechanical Engineering
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Outline of the Presentation

• Lecture
• In-class group activities
• Video Clips
• Homework

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Course Outline

• Lecture - I
• Introduction to Nano-
• Technology in Engineering
• Basic concepts
• Length and time scales
• Nano-structured materials
• - Nanocomposites
• - Nanotubes and nanowire
• Applications and Examples

• Lecture II
• Nano-Mechanics
• Nanoscale Thermal
• and FlowPhenomena
• Experimental
• Techniques
• Modeling and
• Simulation

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Lecture Topics

• We will address some of the key issues of
  nano-technology in Mechanical Engineering.
• Some of the topics that will be addressed are
  nano-structured materials nanoparticles and
  nanofluids, nanodevices and sensors, and
  applications.

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Major Topics in Mechanical Engineering

• Mechanics
• Statics Deals with forces, Moments,
  equilibrium of a stationary body
• Dynamics Deals with body in motion -
  velocity, acceleration, torque, momentum,
  angular momentum.
• Structure and properties of material (Including
  strengths)
• Thermodynamics, power generation, alternate
  energy (power plants, solar, wind, geothermal,
  engines)

• Design of machines and
• structures
• Dynamics system, sensors
• and controls
• Robotics
• Computer-Aided Design
• (CAD/CAM)
• Computational Fluid
• Dynamics (CFD) and
• Finite Element Method
• Fabrication and
• Manufacturing processes

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Diesel Engine Simulation Model
Fuel Cell Design and Development
Flow in micro channel
No slip condition
Slip Conditions
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Length Scales in Sciences and Mechanics
Quantum Mechanics Deals with atoms - Molecular
Mechanics Molecular Networks - Nanomechanics
Nano-Materials - Micromechanics Macro-mechanic
Continuum substance
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Quantum and Molecular Mechanics

• All substances are composed molecules or atoms in
  random motion.
• For a system consisting of cube of 25-mm on each
  side and containing gas with atoms.
• To specify the position of each molecule, we need
  to three co-ordinates and three component
  velocities
• So, in order to describe the behavior of this
  system form atomic view point, we need to deal
  with at least
• equations.
• This is quite a computational task even with the
  most powerful (massively parallel multiple
  processors) computer available today.
• There are two approaches to handle this
  situations Microscopic or Macroscopic model

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Microscopic Vs Macroscopic

• Approach -1 Microscopic viewpoint based on
• kinetic theory and statistical mechanics
• On the basis of statistical considerations and
  probability theory, we deal with average values
  of all atoms or molecules and in connection with
  a model of the atom.
• Approach II Macroscopic view point
• Consider gross or average behavior of a number of
  molecules that can be handled based on the
  continuum assumption.
• We mainly deal with time averaged influence of
  many molecules.
• These macroscopic or average effects can be
  perceived by our senses and measured by
  instruments.
• This leads to our treatment of substance as an
  infinitely divisible substance or continuum.

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Breakdown of Continuum Model

• To show the limit of continuum or macroscopic
  model, let us consider the concept of density
• Density is defined as the mass
• per unit volume and expressed as
• Where is the smallest volume for which
  substance can be assumed as continuum.
• Volume smaller than this will lead to the fact
  that mass is not uniformly distributed, but
  rather concentrated in particles as molecules,
  atoms, electrons etc.
• Figure shows such variation in density as volume
  decreases below the continuum limit.

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Macroscopic Properties and Measurement

• Pressure
• Pressure is defined as the
• average normal-component
• of force per unit area and
• expressed as
• Where is the smallest volume for
  which substance can be assumed as continuum.

Pressure Measurement
For a pressure gauge, it is the average force
(rate of change of momentum) exerted by the
randomly moving atoms or molecules over the
sensors area.
Unit Pascal (Pa) or
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Introduction- Nanotechnology

• Nanoscale uses nanometer as the basic unit of
  measurement and it represents a billionth of a
  meter or one billionth of a part.
• Nanotechnology deals with nanosized particles and
  devices
• One- nm is about 3 to 5 atoms wide. This is very
  tiny when compared normal sizes encounter
  day-to-day.
• - For example this is 1/1000th the width of
  human
• hair.

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• Any physical substance or device with structural
  dimensions below 100 nm is called nanomaterial or
  nano-device.
• Nanotechnology rests on the technology that
  involves fabrication of material, devices and
  systems through direct control of matter at
  nanometer length scale or less than 100 nm.

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• Nanoparticles can be defined as building blocks
  of nanomaterials and nanotechnology.
• Nanoparticles include nanotubes, nanofibers,
  fullerenes, dendrimers, nanowires and may be
  made of ceramics, metal, nonmetal, metal oxide,
  organic or inorganic.
• At this small scale level, the physical, chemical
  and biological properties of materials differ
  significantly from the fundamental properties at
  bulk level.
• Many forces or effects such inter-molecular
  forces, surface tension, electromagnetic,
  electrostatic, capillary becomes significantly
  more dominant than gravity.
• Nanomaterial can be physically and chemically
  manipulated to alter the properties, and these
  properties can be measured using nanoscale
  sensors and gages.

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• A structure of the size of an atom represents one
  of the fundamental limit.
• Fabricating or making anything smaller require
  manipulation in atomic or molecular level and
  that is like changing one chemical form to other.
• Scientist and engineers have just started
  developing new techniques for making
  nanostructures.

The nanoscience is matured. The age of
nanofabrication is here. The age of
nanotechnology - that is the practical use of
nanostructure has just started.
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Nanotechnology in Mechanical Engineering
New Basic Concepts
Nano-Scale Heat Transfer
Nano-Mechanics
Nano-fluidics
Applications
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Applications

• Structural materials
• Nano devices and sensors
• Coolants and heat spreaders
• Lubrication
• Engine emission reduction
• Fuel cell nanoporous electrode/membranes/nanocat
  alyst
• Hydrogen storage medium
• Sustainable energy generation - Photovoltaic
  cells for power conversion
• Biological systems and biomedicine

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Basic Concepts

• Energy Carriers
• Phonon Quantized lattice vibration energy
  with wave nature of propagation
• - dominant in crystalline material
• Free Electrons
• - dominant in metals
• Photon Quantized electromagnetic energy with
  wave nature of propagation
• - energy carrier of radiative energy

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Length Scales

• Two regimes
• I. Classical microscale size-effect domain
  Useful for microscale heat transfer in
  micron-size environment.

Where
mean free path length of the substance
characteristic device dimension
II. Quantum nanoscale size-effect domain
More relevant to nanoscale heat transfer
Where
characteristic wave length of the
electrons
or phonons
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• This length scale will provide the guidelines for
  analysis method- both theoretical and
  experimental methods
• classical microscale domain or nanoscale
  size-effect domain.

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Flow in Nano-channels

• The Navier Stokes (N-S) equation of continuum
  model fails when the gradients of macroscopic
  variables become so steep that the length scale
  is of the order of average distance traveled by
  the molecules between collision.
• Knudsen number ( ) is typical parameter
  used to classify the length scale and flow
  regimes

Kn lt 0.01 Continuum approach with traditional
Navier-Stokes and no-slip boundary conditions
are valid. 0.01ltKnlt0.1 Slip flow regime and
N-S with slip boundary conditions are
applicable 0.1ltKnlt10 Transition regime
Continuum approach completely breaks
Molecular Dynamic Simulation Kn gt 10 Free
molecular regime The collision less Boltzman
equation is applicable.
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Time Scales

• Relaxation time for different collision process
• Relaxation time for phonon-electron
• interaction
• Relaxation time for electron-electron
• interaction
• Relaxation time for phonon-phonon
• interaction

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Nanotechnology Modeling Methods

• Quantum Mechanics
• Atomistic simulation
• Molecular Mechanics/Dynamics
• Nanomechanics
• Nanoheat transfer and Nanofluidics

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Models for Inter-molecules Force

• - Inter-molecular Potential
• Model
• - Inverse Power Law Model or
• Point Centre of Repulsion
  
• Model
• - Hard Sphere Model
• - Maxwell Model
• - Lennard-Jones Potential
• Model

• Inter-molecular Potential Model

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Nanotools

• Nanotools are required for manipulation of matter
  at nanoscale or atomic level.
• Certain devices which manipulate matter at atomic
  or molecular level are Scanning-probe
  microscopes, atomic force microscopes, atomic
  layer deposition devices and nanolithography
  tools.
• Nanolithography means creation of nanoscale
  structure by etching or printing.
• Nanotools comprises of fabrication techniques,
  analysis and metrology instruments, software for
  nanotechnology research and development.
• Softwares are utilized in nanolithography, 3-D
  printing, nanofluidics and chemical vapor
  deposition.

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Nanoparticles and Nanomaterials

• Nanoparticles
• Nanoparticles are significantly larger than
  individual atoms and molecules.
• Nanoparticles are not completely governed by
  either quantum chemistry or by laws of classical
  physics.
• Nanoparticles have high surface area per unit
  volume.
• When material size is reduced the number of atoms
  on the surface increases than number of atoms in
  the material itself. This surface structure
  dominates the properties related to it.
• Nanoparticles are made from chemically stable
  metals, metal oxides and carbon in different
  forms.

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Carbon -Nanotubes

• Carbon nanotubes are hollow cylinders made up of
  carbon atoms.
• The diameter of carbon nanotube is few nanometers
  and they can be several millimeters in length.
• Carbon nanotubes looks like rolled tubes of
  graphite and their walls are like hexagonal
  carbon rings and are formed in large bundles.
• Have high surface area per unit volume
• Carbon nanotubes are 100 times stronger than
  steel at one-sixth of the weight.
• Carbon nanotubes have the ability to sustain high
  temperature 2000 C.

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• There are four types of carbon
• nanotube Single Walled Carbon
• Nanotube (SWNT), Multi Walled
• Xarbon nanotube (MWNT), Fullerene
• and Torus.
• SWNTs are made up of single
• cylindrical grapheme layer
• MWNTs is made up of multiple
• Grapheme layers.
• SWNT possess important electric
• properties which MWNT does not.
• SWNT are excellent conductors, so finds its
  application in miniaturizing electronics
  components.

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Nanocomposites

• Formed by combining two or more nanomaterials to
  achieve better properties.
• Gives the best properties of each individual
  nanomaterial.
• Show increase in strength, modulus of elasticity
  and strain in failure.
• Interfacial characteristics, shape, structure and
  properties of individual nanomaterials decide the
  properties.
• Find use in high performance, lightweight, energy
  savings and environmental protection applications
• - buildings and structures, automobiles
• and aircrafts.

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• Examples of nanocomposites include nanowires
• and metal matrix composites.
• Classified into multilayered structures and
  inorganic or
• organic composites.
• Multilayered structures are formed from
  self-assembly of
• monolayers.
• Nanocomposites may provide heterostructures
  formed from
• various inorganic or organic layers, leading
  to multifunctional
• materials.
• Nanowires are made up of various materials and
  find its
• application in microelectronics for
  semiconductor devices.

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Nanostructured Materials

• All the properties of nanostructured are
  controlled by changes in atomic structure, in
  length scales, in sizes and in alloying
  components.
• Nanostructured materials are formed by
  controlling grain sizes and creating increased
  surface area per unit volume.
• Decrease in grain size causes increase in
  volumetric fraction of grain boundaries, which
  leads to changes in fundamental properties of
  materials.

Different behavior of atoms at surface has been
observed than atom at interior. Structural and
compositional differences between bulk material
and nanomaterial cause change in properties.
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• The size affected properties are color, thermal
  conductivity,
• mechanical, electrical, magnetic etc.
• Nanophase metals show increase in hardness and
  modulus
• of elasticity than bulk metals.
• Nanostructured materials are produced in the
  form of
• powders, thin films and in coatings.
• Synthesis of nanostructured materials take place
  by Top
• Down or Bottom- Up method.
• - In Top-Down method the bulk solid is
  decomposed into
• nanostructure.
• - In Bottom-Up method atoms or molecules
  are
• assembled into bulk solid.
• The future of nanostructured materials deal with
  controlling
• characteristics, processing into and from
  bulk material and
• in new manufacturing technologies.

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Nanofluids

• Nanofluids are engineered colloid formed with
  stable suspemsions of solid nano-particles in
  traditional base liquids.
• Base fluids Water, organic fluids, Glycol, oil,
  lubricants and other fluids
• Nanoparticle materials
• - Metal Oxides
• - Stable metals Au, cu
• - Carbon carbon nanotubes (SWNTs,
  MWNTs),
• diamond, graphite, fullerene,
  Amorphous Carbon
• - Polymers Teflon
• Nanoparticle size 1-100 nm

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Nanofluid Heat Transfer Enhancement

• Thermal conductivity enhancement
• - Reported breakthrough in substantially
  increase ( 20-30) in thermal conductivity of
  fluid by adding very small amounts (3-4) of
  suspended metallic or metallic oxides or
  nanotubes.
• Increased convective heat transfer
  characteristic for heat transfer fluids as
  coolant or heating fluid.
• -

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Nanofluids and Nanofludics

• Nanofluids have been investigated
• - to identify the specific transport
  mechanism
• - to identify critical parameters
• - to characterize flow characteristics in
  macro,
• micro and nano-channels
• - to quantify heat exchange performance,
• - to develop specific production,
  management
• and safety issues, and measurement and
• simulation techniques

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Nano-fluid Applications

• Energy conversion and energy storage system
• Electronics cooling techniques
• Thermal management of fuel cell energy systems
• Nuclear reactor coolants
• Combustion engine coolants
• Super conducting magnets
• Biological systems and biomedicine

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Nano-Biotechnology

• When the tools and processes of nanotechnology
  are applied towards biosystems, it is called
  nanobiotechnology.
• Due to characteristic length scale and unique
  properties,
• nanomaterials can find its application in
  biosystems.
• Nanocomposite materials can play great role in
  development of materials for biocompatible
  implant.
• Nano sensors and nanofluidcs have started
  playing an important role in diagnostic tests and
  drug delivering system for decease control.
• The long term aim of nano-biotechnology is to
  build tiny devices with biological tools
  incorporated into it diagonistic and treatment..

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National Nanotechnology Initiative in Medicine

• Improved imaging (See www.3DImaging.com)
• Treatment of Disease
• Superior Implant
• Drug delivery system and treatment using
  Denrimers, Nanoshells, Micro- and Nanofluidics
  and Plasmonics

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- In order to improve the durability and
bio-compatibility, the implant surfaces are
modified with nano-thin film coating (Carbon
nano-particles). - An artificial knee joint or
hip coated with nanoparticles bonds to the
adjacent bones more tightly.

• Nano-particles delivers treatment to targeted
  area or targeted tumors
• - Release drugs or release radiation to heat up
  and destroy tumors or cancer cells

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Self Powered Nanodevices and Nanogenerators

• Nanosize devices or machined need nano-size power
  generator call nanogenerators without the need of
  a battery.
• Power requirements of nanodevices or nanosystems
  are generally very small
• in the range of nanowatts to microwatts.
• Example Power source for a biosensor
• - Such devices may allow us to develop
  implantable biosensors that can continuously
  monitor humans blood sugar level

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• Waste energy in the form of vibrations or even
  the human pulse could power tiny devices.
• Arrays of piezoelectric could capture and
  transmit that waste energy to nanodevices
• There are many power sources in a human body
• - Mechanical energy, Heat energy,
  Vibration energy,
• Chemical energy
• A small fraction of this energy can be converted
  into electricity to power nano-bio devices.
• Nanogenerators can also be used for other
  applications
• - Autonomous strain sensors for structures
  such as bridges
• - Environmental sensors for detecting
  toxins
• - Energy sensors for nano-robotics
• - Microelectromecanical systems (MEMS) or
  
• nanoelectromechanical system (NEMS)
• - A pacemakers battery could be
  charged without
• requiring any replacement

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Nano-sensor and Nano-generator
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Example Piezoelectric Nanogenerator

• Piezoelectric Effect
• Some crystalline materials generates
  electrical voltage when mechanically stressed
• A Typical Vibration-based Piezoelectric
  Transducer
• - Uses a two-layered beam with one end fixed
  
• and other end mounted with a mass
• - Under the action of the gravity the beam is
  bent with
• upper-layer subjected to tension and
  lower-layer
• subjected to tension.

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Conversion of Mechanical Energy to Electricityin
a Nanosystem

Gravity do not play any role for motion in
nanoscale. Nanowire is flexed by moving a ridged
from side to side.
Array of nanowires (Zinc Oxide) with
piezoelectric and semiconductor properties
Rectangular electrode with ridged
underside. Moves side to side in response to
external motion of the structure
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Example Thermo Electric Nano-generator

• Thermoelectric generator relies on the Seebeck
  Effect where an electric potential exists at the
  junction of two dissimilar metals that are at
  different temperatures.
• The potential difference or the voltage produced
  is proportional to the temperature difference.
• - Already used in Seiko Thermic Wrist
  Watch

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Bio-Nano Generators

• Questions
• 1. How much and what different kind of
  energy
• does body produce?
• 2. How this energy source can be utilized
  to
• produce power.
• 3. What are the technological challenges?