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Nanotechnology
in
Mechanical Engineering
and
Manufacturing Engineering
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Outline of YOUR Presentation
Lecture
In-class group activities
Video Clips
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Course Outline
Introduction to
Nano-Technology in Engineering
Basic concepts
Length and time scales
Nano-structured materials
- Nanocomposites
- Nanotubes and nanowire
Applications and Examples
Nano-Mechanics
Nanoscale Thermal and FlowPhenomena
Experimental Techniques
Modeling and Simulation
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
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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
6 x = 10µm x = 250µm x = 500µm x = 750µm x = 1000
µm
Diesel Engine Simulation Model
Fuel Cell Design and Development
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:
NanoMaterials
-Micromechanics:
Macro-mechanic:
Continuum substance
Quantum and Molecular Mechanics
All substances are composed molecules or atoms inrandom motion.
For a system consisting ofcubeof 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.
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Microscopic Vs Macroscopic
Approach -1:Microscopic viewpointbased 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 thecontinuum 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 orcontinuum.
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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 asWhere 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.
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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 sensor s area. Unit: Pascal (Pa) or
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.
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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 includenanotubes,nanofibers,fullerenes, dendrimers,nanowiresand may be made of ceramics, metal, nonmetal, metal oxide, organic or inorganic.
At thissmall scalelevel, the physical, chemical and biological properties of materialsdiffer significantly from the fundamental properties atbulk level.
Manyforces or effectssuch inter-molecular forces, surface tension, electromagnetic, electrostatic, capillary becomes significantly more dominant than gravity.
Nanomaterial can bephysically and chemically
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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.
Nanotechnology in Mechanical
Engineering
New Basic Concepts
Nano-Mechanics Nano-Scale
Heat Transfer
Nano-fluidics
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Applications
Structural materials
Nano devices and sensors
Coolants and heat spreaders
Lubrication Engine emission reduction
Fuel cell nanoporous
electrode/membranes/nanocatalyst
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
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Length Scales
Two regimes:
I. Classical microscale size-effect domain Useful for microscale heat transfer in micron-size environment.
Where
characteristic device dimension
mean free path length of the substance
II. Quantum nanoscale size-effect domain More relevant to nanoscale heat transfer
Where
characteristic wave length of the electrons or phonons
This length scale will provide the guidelines for
analysis method- both theoretical and
experimental methods:
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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 < 0.01: Continuum approach with traditional Navier-Stokes and no-slip boundary conditions are valid.
0.01<Kn<0.1: Slip flow regime and N-S with slip boundary conditions are applicable
0.1<Kn<10: Transition regime–Continuum approach completely
breaks–Molecular Dynamic Simulation
Kn > 10 : Free molecular regime–The collision less Boltzman
equation is applicable.
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Time Scales
Relaxation timefor different collision process: Relaxation time forphonon-electron
interaction:
Relaxation time forelectron-electron
interaction:
Relaxation time forphonon-phonon
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Nanotechnology: Modeling
Methods
Quantum Mechanics
Atomistic simulation
Molecular Mechanics/Dynamics
Nanomechanics
Nanoheat transfer and Nanofluidics
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
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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 areScanning-probe microscopes, atomic force microscopes,atomic layer deposition devicesandnanolithography 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.
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Carbon -Nanotubes
Carbon nanotubes are hollow cylinders made up of carbon atoms. Thediameterof carbon nanotube is few nanometersand 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.
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
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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.31
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.Nanostructured 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.
The size affected properties are color, thermal conductivity, mechanical, electrical, magnetic etc.
Nanophase metals show increase in hardness and modulusof 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.
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Nanofluids
Nanofluidsare 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
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
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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..38
National Nanotechnology Initiative
in Medicine
Improved imaging (See: www.3DImaging.com)
Treatment of Disease
Superior Implant
Drug delivery system and treatment using
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-Nano-particles delivers treatment to targeted area or targeted tumors
- Release drugs or release radiation to heat up and destroy tumors or cancer cells
- 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.
Self Powered Nanodevices and
Nanogenerators
Nanosize devices or machined need nano-size power generator callnanogeneratorswithout 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
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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 manypower 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 - Autonomousstrain sensorsfor structures such as bridges - Environmental sensors for detecting toxins
- Energy sensorsfor nano-robotics
- Microelectromecanical systems (MEMS) or nanoelectromechanical system (NEMS)
- A pacemaker s battery could be charged without requiring any replacement
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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.
Conversion of Mechanical Energy to Electricity
in a Nanosystem
Rectangular electrode with ridged underside.
Moves side to side in response to external motion of the Array of
nanowires (Zinc Oxide) with piezoelectric and semiconductor properties
Gravity do not play any role for motion in nanoscale.
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Example: Thermo Electric Nano-generator
Thermoelectric generator relies on theSeebeck Effect where anelectric potentialexists 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 inSeiko 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.
