This document discusses smart materials and provides examples. It defines smart materials as materials that can significantly change one or more properties in a controlled way due to external stimuli like stress, temperature, or electric fields. Examples given include piezoelectric materials that produce voltage when stressed, shape memory alloys that can remember their original shape, and pH sensitive polymers that change with pH levels. Applications described are uses in medical devices, aerospace, and more. Biomimetics and intelligent structures are also summarized briefly.

1. Dr. Jatinder Kapoor
Professor
Dept. of Mechanical
Engineering
GNDEC, Ludhiana
Smart Materials

2. What is a Smart Material?
 Smart materials are materials that have one or more
properties that can be significantly altered in a controlled
fashion by external stimuli, such as stress, temperature,
moisture, pH, electric or magnetic fields.
 The change in the material can also be reversible, as a change
in stimulus can bring the material back to its previous state.

3. What are the examples?
 Piezoelectric materials
 Shape memory alloys
 Magnetic shape memory alloys
 PH sensitive polymers
 Halochromic materials
 Chromogenic systems

4. What are Piezoelectric materials?
 Piezoelectric materials are materials that produce a
voltage when stress is applied. Since this effect also
applies in the reverse manner, a voltage across the
sample will produce stress within the sample. Suitably
designed structures made from these materials can
therefore be made that bend, expand or contract when a
voltage is applied.
 Buzzers are piezoelectric.

5. Shape Memory Alloys (SMAs)
 Metals that exhibit pseudo-elasticity and the “Shape Memory
Effect”
 The basic principle behind SMAs is that a solid state phase
change occurs in these materials.
 They switch between states ofAustenite and Martensite.
Shape memory alloys and shape memory polymers are
thermo responsive materials, where deformation can be
induced and recovered through temperature changes.


6. What are shape memory alloys?
 An example is NiTinolTM (NickelTitanium)
 Above its transformation temperature, Nitinol is
superelastic, able to withstand a large amount of
deformation when a load is applied and return to its
original shape when the load is removed. Below its
transformation temperature, it displays the shape
memory effect.When it is deformed it will remain in
that shape until heated above its transformation
temperature, at which time it will return to its original
shape.

7. Magnetic SMA
 Magnetic Shape Memory alloys are materials that change their
shape in response to a significant change in the magnetic field.

8. Example of SMA

9. Application of SMA
 Nitinol is used in medicine for stents:
A collapsed stent can be inserted into
a vein and heated (returning to its
original expanded shape) helping to
improve blood flow.Also, as a
replacement for sutures where
nitinol wire can be weaved through
two structures then allowed to
transform into it's pre-formed shape
which should hold the structures in
place.

10. Appplications of SMA
 Popular SMAs are NiTi, CuZnAl, and CuAlNi
 Applications include:
 Aeronautical
 Making flexible wings using shape memory wires
 Medicine
 Bone plates made of NiTi
 Bioengineering
 Muscle wires that can mimic human movement

11. Smart Gels
 A smart gel is a material that expands or contracts in response to
external stimuli.
 A smart gel consists of fluid that exists in a matrix of polymer(s).
 Stimulus can include
 Light
 Magnetic
 pH
 Temperature
 Electrical
 Mechanical
 Stimulus will alter the polymer that makes it more or less
hydrophillic.

12. Tanaka experiment
Modeled after T. Tanaka, Science 19 November 1999: Vol. 286. no. 5444, pp. 1543 - 1545

13. Applications of Smart Gels
 Medical
 Drug release
 Organ replacement
 Muscle replication
 Industrial
 Shake gels
 Shock absorbers

14. Rheological Materials
 Material that can change its physical state very quickly in
response to a stimulus
 Stimulus include
 Electrical
 Magnetic
 Ferromagnets
 Magnetic field aligns ferromagnetic molecules in order in order to
achieve solid state structure
o Nanoparticles reduce IUT effect (In UseThickening)

15. Example of Magnetic Field on
Rheological Material

16. Applications of Rheological Materials
 MR materials
 Structural Support
 Dampers to minimize vibrational shock from wind and seismic activity.
 Industrial
 Break fluids
 Shock absorbers

17. Magnetostrictive materials
 Material that stretches or shrinks when a magnetic field is
applied.
 Conversely, when a mechanical force is applied on the
material, a magnetic field is induced.
 Ferromagnets
 Magnetic field can be used to create an electric current

18. Applications of Magnetorestrictive
Materials
 More efficient fuel injection system
 Specific amounts of fuel
 Higher frequency

19. Fullerenes
 A fullerene is any series of hollow
carbon molecules that form either a
closed cage, as in a buckyball, or a
cylinder, like a carbon nanotube.
 Most researched/utilized fullerene is
the carbon-60 molecule (truncated
icosaheedron)
 Three nanotubes can be made by
varying the chiral angle.
 Arm-chair
 Zig-zag
 Chiral
 Chiral angle determines conductivity

20. Applications of fullerenes
 Superconductors
 By doping fullerenes with three variable atoms, a
superconducting state can be achieved.
 Medical
 Atoms can be trapped in a buckyball, in order to create a
biological sponge.
 HIV protease inhibitor
 A buckyball can be inserted in the HIV protease active site in
order to stop replication.

21. PH sensitive polymers
 pH-sensitive polymers are materials which swell/collapse when
the pH of the surrounding media changes.
 The sensor is prepared by entrapping within a polymer matrix a
pH sensitive dye that responds, through visible colour changes (see
next slide) to spoilage volatile compounds that contribute to a
quantity known asTotalVolatile Basic Nitrogen (TVB-N).

22. PH sensitive polymers
 The sample is outside the package.The others are all inside.
www.dcu.ie/chemistry/asg/pacquita/

23. Halochromic Materials
 Halochromic materials are commonly materials that change their
colour as a result of changing acidity. One suggested application is
for paints that can change colour to indicate corrosion in the metal
underneath them.

24. Chromogenic systems
 Chromogenic systems change colour in response to electrical,
optical or thermal changes. These include electro chromic
materials, which change their colour or opacity on the application
of a voltage (e.g. liquid crystal displays), thermochromic materials
change in colour depending on their temperature, and
photochromic materials, which change colour in response to light
- for example, light sensitive sunglasses that darken when exposed
to bright sunlight.

25. Electrochromic
 Flip a switch and an
electrochromic window can
change from clear to fully
darkened or any level of tint in-
between.
 The action of an electric field
signals the change in the
window's optical and thermal
properties. Once the field is
reversed, the process is also
reversed. The windows operate
on a very low voltage -- one to
three volts -- and only use
energy to change their
condition, not to maintain any
particular state.

26. Thermochromic
 Kettles that change colour and signs that
glow-in-the-dark are two recent
examples of products becoming
‘smarter’ as a result of new materials.
Colour-changing thermochromic
pigments are now routinely made as inks
for paper and fabrics – and incorporated
into injection moulded plastics. A new
type of phosphorescent pigment, capable
of emitting light for up to 10 hours, has
opened up entirely new design
opportunities for instrumentation, low-
level lighting systems etc. Warm Cool
http://www.mutr.co.uk/catalog/index.php?cPath=79

27. Photochromic
 Photochromism is the reversible transformation of colour upon exposure to
light.This phenomenon is illustrated in sun glasses.

28. QTC
 QuantumTunneling Composites (or QTCs) are composite materials of metals and non-
conducting elastomeric binder, used as pressure sensors.
 As the name implies, they operate using quantum tunneling: without pressure, the
conductive elements are too far apart to conduct electricity; when pressure is applied, they
move closer and electrons can tunnel through the insulator.The effect is far more
pronounced than would be expected from classical (non-quantum) effects alone, as classical
electrical resistance is linear (proportional to distance), while quantum tunneling is
exponential with decreasing distance, allowing the resistance to change by a factor of up to
1012 between pressured and unpressured states.
 QTCs were discovered in 1996 and PeraTech Ltd was established to investigate them
further.
 http://www.mutr.co.uk/catalog/product_info.php?products_id=1144

29. QTC

30. QTC

31. Smart Grease
www.tep.co.uk

32. Smart materials
 smart materials have appropriate responses
 photochromic glass
• darkens in bright light
 low melting point wax in a fire sprinkler
• blocks the nozzle until it gets hot
 acoustic emission
• sounds emitted under high stress
 embedded optical fibres
• broken ends reflect light back
 microporous breathable fabrics

33. Waterproof clothing
(material or structure ?)
 Goretex®
 micro-porous expanded PTFE (Polytetrafluoroethylene )
discovered in 1969 by Bob Gore
 ~ 14 x 1012 micropores per m².
 each pore is about 700x larger than
a water vapour molecule
 water drop is 20,000x larger than a pore

34. Goretex:

35. Intelligent structures (IS)
 composites made at low temp
  can embed additional components
 control can decide on novel response

36. Intelligent structures (IS)
 embed three elements of the system:
 sensors
 signal processing and control
 actuators

37. Sensors
 strain gauges
 microdieletric interdigitated sensors
 optical fibres
 piezoelectric crystals
 shape memory alloys
 sensitive semiconductor chip
 giant magnetoimpedance (GMI) wires

38. Optical Fibre Bragg Grating (OFBG)
Non-Destructive Testing of
Fibre-Reinforced Plastics
Composites
image from http://en.wikipedia.org/wiki/Image:Fbg.GIF

39. Signal processing
 issues with data fusion
for large sensor arrays

40. Actuators
 hydraulic, pneumatic and electric
 piezoelectric crystals
 shape changes when voltage applied
 shape memory materials
 shape changes at a specific temperature
 alloys = SMA .... polymers = SMP
 magneto-rheological (MR) fluids
 viscosity changes with magnetic field
 electro-rheological (ER) fluids
 viscosity changes with electric field

41. Magneto-rheological (MR) fluids
Electro-rheological (ER) fluids

42. Intelligent Structures: applications
 artificial hand
 SMA fingers controlled by
nerve (myoelectric) signals
 vibration damping
 apply electric field to ER fluid
 skyscraper windows
 acoustic emission warning system

43. Biomimetics
 also known as
 bionics
 biognosis
 synthetic biology
Biomimetic materials are materials developed
using inspiration from nature.This may be useful in the design
of composite materials. Natural structures have inspired and
innovated human creations. Notable examples of these natural
structures include: honeycomb structure of the beehive,
strength of spider silks, bird flight mechanics, and shark
skin water repellency

44. Biomimetics
 the concept of taking ideas from nature to implement in another
technology
 Chinese silk cultivation begins c.4000BC
• ColinThubron, Shadow of the Silk Road, Chatto &Windus, 2006.
 Daedalus' wings - early design failures
 gathering momentum due to the
ever increasing need for
sympathetic technology

45. Biomimetics
 Notable innovations
from understanding nature
 Velcro
 Gecko tape
 Lotus effect self-cleaning surfaces
 Drag reduction by shark skin
 PlateletTechnologyTM for pipe repair
 Smart-fabric
 ElekTex™
 Chobham armour vs nacre

46. Biomimetics
 Velcro
 small hooks enable seed-bearing burr
to cling to tiny loops in fabric

47. Gecko tape
image from
http://www.netcomposites.com/news.asp?3922
 geckos to hang single-toed from sheer walls and walk along
ceilings using fine hairs on feet
 University of California - Berkeley created an array of
synthetic micro-fibres
using very high friction
to support loads on smooth surfaces.

48. Biomimetics
 Lotus effect self-cleaning surfaces
 surface of leaf water droplet on leaf
 Image from http://library.thinkquest.org/27468/e/lotus.htm

49. Biomimetics: Lotus effect
 most efficient self-cleaning plant
= great sacred lotus
(Nelumbo nucifera)
 mimicked in paints and
other surface coatings
 pipe cleaning in oil refineries (Norway)
Images from
 http://library.thinkquest.org/27468/e/lotus.htm
 http://www.villalachouette.de/william/lotusv2.gif
 http://www.nees.uni-bonn.de/lotus/en/vergleich.html

50. Biomimetics
 drag reduction by shark skin
 special alignment and grooved structure
of tooth-like scales embedded in shark skin
decrease drag and thus
greatly increase swimming proficiency
 Airbus fuel consumption down 1½%
when “shark skin” coating applied to aircraft
o Image from http://www.pelagic.org/biology/scales.html

51. Smart-fabric
 pine-cone model
 adapts to changing temperatures
by opening when warm or shutting
tight if cold

52. ElekTex™
 looks and feels like a fabric
 capable of electronic x-y-z sensing
 fold it, scrunch it or wrap it
 lightweight, durable, flexible
 cost competitive
 cloth keyboards and keypads
 details: http://www.electrotextiles.com

53. Self-sensing tyres
 The use of tyre pressure management systems (TPMS) in the
automotive industry is growing, as car manufacturers strive
for the most efficient use of fuel in their vehicles. Millions
fewer batteries would be manufactured ifTPMS were
powered by vibrations in the rubber of the tyre itself, and the
same logic applies to many other types of sensor.
 Chris Bowen, from the University of Bath, said while energy
harvesting materials are unlikely to generate enough power
for an appliance such as a light, they could power a sensor.

54. Acknowledgements
 Various websites from which
images have been extracted