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.

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 of Austenite 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 (Nickel Titanium)
 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 Use Thickening)

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 as Total Volatile 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
 Quantum Tunneling 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
• Colin Thubron, 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
 Platelet TechnologyTM 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 if TPMS 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