9. Smart Materials

Question 1

Define a Smart Material

Answer 1

a material that reacts to an external stimulus or input

Question 2

List the 7 types of external stimulus

Answer 2

heat
pressure
moisture
stress
pH level
light (including uv)
electricity

Question 3

What external stimulus does a thermochromic pigment react to?

Answer 3

Heat

Question 4

Thermochromic pigments are added to a variety of materials including fabrics, plastics, paint. Give an example of a product which uses thermochromics pigment?

Answer 4

baby bottles
fridge magnet
temp sensitive Coffee cups

Question 5

What external stimulus does a photochromic pigment react to?

Answer 5

uv light

Question 6

What everyday summer face wear could use a photochromic pigment?

Answer 6

photochromic sunglasses

Question 7

What external stimulus does a shape memory alloy react to?

Answer 7

heat or electricity

Question 8

Nitinol is shape memory alloy. What 2 metals make up this alloy?

Answer 8

Nickel

Titanium

Question 9

Give an example of a product which uses nitinol in medical science?

Answer 9

self expanding surgical stents in arteries and veins

braces for teeth

Question 10

What 2 external stimuli does a self healing material react to?

Answer 10

1. stress (forces) cause fractures which release resin to fill the cracks
2. moisture causes release of bacteria which fills crack with limestone

Question 11

Quantum tunnelling composites have the ability to act as an electrical insulator or a conductor. What external stimulus can cause this switch?

Answer 11

pressure on the material

eg lighting, harder you press the lighter it gets

Question 12

What external stimuli does a piezoelectric material react to?

Answer 12

pressure

Question 13

Airbags in cars use piezoelectric actuators. How do these work?

Answer 13

impact of crash - puts pressure on piezoelectric actuator - sends electrical current - deploys airbag

Question 14

What external stimuli does a litmus paper react to?

Answer 14

pH - acid or alkaline