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Engineering > Smart Materials > Flashcards

Smart Materials Flashcards

1
Q

What are smart materials?

A

Materials whose properties respond to external stimuli (environmental and physical changes) without human intervention.
- They usually change one physical property

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2
Q

Examples of properties smart materials could change

A

usually one of

  • colour
  • viscosity
  • dimensions
  • electrical conductivity
  • stiffness
  • opacity
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3
Q

List potential stimuli for smart materials

A
  • light (eg UV)
  • temperature changes
  • physical pressure
  • electrical current
  • magnetic fields
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4
Q

How do smart materials adapt their properties?

A

Due to changes in the natural structure of the material

• within the material, atoms and molecules rearrange themselves to give unique properties

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5
Q

Defining characteristics of SMAs

A

Shape memory alloys
Materials that return to their original shape or form, usually when reheated
• Some change when exposed to a magnetic field or an electric current

Can be one-way or two-way

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6
Q

Materials that return to their original shape or form, usually when reheated

A

Shape memory alloys (SMA)

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7
Q

Compare the two types of SMAs

A

One-way:
- remembers its shape either above or below its memory temperature
the metal can be bent or stretched and will hold those shapes until heated above the transition temperature. Upon heating, the shape changes to its original. When the metal cools again, it will retain the shape, until deformed again.
Two-way:
- remembers two forms or shapes at two different temperatures

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8
Q

uses of SMAs

A
  • used in surgery eg stents that expand and contract based on body temperature
  • glasses frames that self-mend (fixed by optician)

Nitinol

  • used in robotics and prosthetics to create artificial movement
  • switchgear
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9
Q

Typical properties of SMAs

A
  • Light and strong
  • Biocompatible and resistant
  • Poor fatigue properties (can break under bending, twisting, and compression)
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10
Q

What is Nitinol?

A
  • alloy of titanium and nickel
  • properties of SMA and superelasticity
  • Nitinol wires/tubes can change their dimensions with temperature
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11
Q

What are QTCs?

A

quantum tunnelling composites

  • a material that is an insulator at normal conditions
  • when pressure is applied, it becomes an electrical conductor
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12
Q

Uses of QTCs

A
  • Sports clothing with music control
  • flexible keyboards
  • pressure sensors in buildings
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13
Q

How do QTCs work?

A

Consist of an insulator (polymer)
Particles of a conducting material are suspended within this
- when pressed together, can conduct
more pressure = less resistance

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14
Q

What are thermochromic materials?

A

change their colour depending on the temperature

- can come as an ink

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15
Q

uses of thermochromic materials

A
  • Temperature indicators/sensors (eg forehead thermometers)
  • Some clothing
  • Colour-changing novelty mugs/spoons
  • Battery power indicators
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16
Q

What are photochromic materials?

A

these pigments reversibly change colour when exposed to light (EM)
- can come as an ink

17
Q

Uses of photochromic materials

A
  • Photochromic glasses lenses that take on a dark tint in UV sunlight exposure
18
Q

What are viscoelastic materials?

A

Smart grease; motion-control gels

Controls the release of energy (uniformly) — controls motion

19
Q

Uses of viscoelastic materials

A
  • slowing down and regulate speed of a simple rubber band mechanism as it unwinds in a model plane.
  • damping for tall buildings that vibrate under wind/earthquakes
  • impact absorption: car bumpers
  • noise and vibration absorption in machinery
20
Q

Name for materials that conduct under physical pressure

A

QTC quantum tunnelling composites

21
Q

Name for motion-control gels

A

Smart grease (viscoelastic)

22
Q

Name for materials that change colour under light

A

Photochromic

23
Q

Name for materials that change colour under temperature

A

Thermochromic

24
Q

Name for materials that product electrical pulses under impact

A

Piezoelectric materials

25
Q

What are SMPs?

A

shape-memory polymers. return to their original shape when heated
- takes form of plastics and foams

26
Q

Examples of SMPs

A

Matresses
car bumpers that can repair after minor collisions
helmets
gum-shields

27
Q

What are electrochromic materials?

A

colour or opacity controlled by applying a voltage to the material eg frosted/clear glass

28
Q

Uses of electrochromic materials

A
  • Security screens
  • Blinds
  • Temperature control for energy-efficient buildings (control transmittence of near infrared light based on season)
29
Q

What are piezoelectric materials?

A

eg quartz

  • produces a small electrical impulse (voltage) when pressed or impacted
  • vibrates if passed an electric current
30
Q

Uses of piezoelectric materials

A
  • Spark generators for cookers
  • Sensors that check bridge integrity
  • Triggering airbag systems in cars
  • Alarms and speakers eg for toys (loud noise for not much power input)
31
Q

What are hydrochromic materials?

A

change colour with contact with water

good for sensors

32
Q

How could nanotechnology be used as a coating for surfaces?

A
  • Waterproofing
  • Low friction
  • Prevent dust sticking to glass
33
Q

How can nanotechnology be used with other materials?

A

to improve properties eg elasticity, stiffness

Engineering (5 decks)

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