1.2 Performance characteristics of materials - Smart Materials Flashcards
What are smart materials? (2)
- 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
Examples of smart materials (6)
- SMA, e.g. nitinol
- Thermochromic pigment
- Phosphorescent pigment
- Photochromic pigment
- Electroluminescent wire
- Piezoelectric material
How do SMAs (shape memory alloys) , e.g nitinol work? (2)
- 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
Uses of Shape memory alloys, e.g nitinol (4)
- dental braces
- self-closing windows
- aeroplane wing flaps
- bioengineering e.g stents, bone plates and screws
How does thermochromic pigment work?
it changes in response to temperature change
Uses of thermochromic pigment (5)
- thermometers
- colour change mugs and kettles
- food packaging to indicate food is hot or cool for drinks
- baby feeding spoons
- battery charge indicator strips
How does phosphorescent pigment work?
Absorbs light energy during the day and ‘re-emits’ the light enrgy when its dark
Uses of phosphorescent pigment (2)
- Fire exit signs
- ‘glow in the dark’ products such as adhesive stars, masks, night lights, watch hands
How does photochromic pigment work?
changes colour with light intensity
Uses of photochromic pigment (3)
- Welding goggles
- Reactive spectacle lenses
- Security markers that show under UV light
How does Electroluminescent wire work?
thin copper wire coated in a phosphorescent material which glows in response to an alternating current
How does piezoelectric material work? (2)
- gives off a small electrical charge when deformed
- increases in size (up to 4%) when an electrical current is passed through it
Uses of electroluminescent wire (4)
- glow bracelets
- interweaving for clothing
- home decoration
- outdoor decorative lighting
Uses of piezoelectric material (5)
- airbag sensors in cars
- lighters for barbecues
- vibration damping in tennis racquets
- musical greeting cards
- pressure sensors
What makes thermochromatic film suitable for thermometers? (4)
- 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
