11 - Smart Materials

Question 1

What are smart materials? (2)

Answer 1

• 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

Question 2

Examples of smart materials (6)

Answer 2

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

Question 3

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

Answer 3

• 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

Question 4

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

Answer 4

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

Question 5

How does thermochromic pigment work?

Answer 5

it changes in response to temperature change

Question 6

Uses of thermochromic pigment (5)

Answer 6

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

Question 7

How does phosphorescent pigment work?

Answer 7

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

Question 8

Uses of phosphorescent pigment (2)

Answer 8

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

Question 9

How does photochromic pigment work?

Answer 9

changes colour with light intensity

Question 10

Uses of photochromic pigment (3)

Answer 10

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

Question 11

How does Electroluminescent wire work?

Answer 11

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

Question 12

Uses of electroluminescent wire (4)

Answer 12

• glow bracelets
• interweaving for clothing
• home decoration
• outdoor decorative lighting

Question 13

How does piezoelectric material work? (2)

Answer 13

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

Question 14

Uses of piezoelectric material (5)

Answer 14

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

Question 15

What makes thermochromatic film suitable for thermometers? (4)

Answer 15

• 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

Question 16

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

Answer 16

• 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

Question 17

Properties of shape memory alloys (SMAs) (3)

Answer 17

• Very elastic
• High ductility
• Corrosion resistant

Question 18

How are SMAs suitable for dental braces?

Answer 18

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

Question 19

Exam tip - Answer structure (4)

Answer 19

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