11 - Smart Materials Flashcards

1
Q

What are smart materials? (2)

A
  • Are materials whose physical properties change in response to an input or change in the environemnt, such as electricity, pressure, temperature or light
  • Many products utilise smart materials often bringing benefits such as increased safety and/or ease of use
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2
Q

Examples of smart materials (6)

A
  • SMA, e.g. nitinol
  • Thermochromic pigment
  • Phosphorescent pigment
  • Photochromic pigment
  • Electroluminescent wire
  • Piezoelectric material
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3
Q

How do SMAs (shape memory alloys) , e.g nitinol work? (2)

A
  • It changes in response to a change in temperature or electrical input
  • e.g nitinol wire in dental braces changes length in response to a change in temperature
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4
Q

Uses of Shape memory alloys, e.g nitinol (4)

A
  • dental braces
  • self-closing windows
  • aeroplane wing flaps
  • bioengineering e.g stents, bone plates and screws
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5
Q

How does thermochromic pigment work?

A

it changes in response to temperature change

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6
Q

Uses of thermochromic pigment (5)

A
  • thermometers
  • colour change mugs and kettles
  • food packaging to indicate food is hot or cool for drinks
  • baby feeding spoons
  • battery charge indicator strips
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7
Q

How does phosphorescent pigment work?

A

Absorbs light energy during the day and ‘re-emits’ the light enrgy when its dark

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8
Q

Uses of phosphorescent pigment (2)

A
  • Fire exit signs
  • ‘glow in the dark’ products such as adhesive stars, masks, night lights, watch hands
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9
Q

How does photochromic pigment work?

A

changes colour with light intensity

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10
Q

Uses of photochromic pigment (3)

A
  • Welding goggles
  • Reactive spectacle lenses
  • Security markers that show under UV light
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11
Q

How does Electroluminescent wire work?

A

thin copper wire coated in a phosphorescent material which glows in response to an alternating current

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12
Q

Uses of electroluminescent wire (4)

A
  • glow bracelets
  • interweaving for clothing
  • home decoration
  • outdoor decorative lighting
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13
Q

How does piezoelectric material work? (2)

A
  • gives off a small electrical charge when deformed
  • increases in size (up to 4%) when an electrical current is passed through it
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14
Q

Uses of piezoelectric material (5)

A
  • airbag sensors in cars
  • lighters for barbecues
  • vibration damping in tennis racquets
  • musical greeting cards
  • pressure sensors
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15
Q

What makes thermochromatic film suitable for thermometers? (4)

A
  • It changes colour in response to temperature change
  • The colour change, such as red for hot, makes it easier to read than small numbers or lines as used on traditional thermometers
  • It is a non-toxic material, therefore much safer to use than mercury thermometers e.g for taking the temperature of a young child
  • It can be incorporated into a film strip, making it flexible enough to go on to a forehead when taking a temperature reading
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16
Q

Why are shape memory alloys (SMAs) suitable for their uses? (3)

A
  • They respond to a change in temperature e.g triggers for fire alarm systems, sprinkler systems, hot water valves in showers, industrial greenhouse windows
  • They repair malformed or damaged products e.g spectacle frames which have been distorted can return to their original shape when heated to the transition temperature
  • Responding with movement to a electrical signal e.g artificial muscles in robot arms and electric door locks
17
Q

Properties of shape memory alloys (SMAs) (3)

A
  • Very elastic
  • High ductility
  • Corrosion resistant
18
Q

How are SMAs suitable for dental braces?

A

Can be designed to change at body temperature; when the braces are placed in the mouth, the wire maintains a constant tension

19
Q

Exam tip - Answer structure (4)

A

1 - include original state

2 - what input is used e,g colour, heat etc

3- how this makes the material change

4 - what changes take place