11 - 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
Uses of electroluminescent wire (4)
- glow bracelets
- interweaving for clothing
- home decoration
- outdoor decorative lighting
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 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
Why are shape memory alloys (SMAs) suitable for their uses? (3)
- 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
Properties of shape memory alloys (SMAs) (3)
- Very elastic
- High ductility
- Corrosion resistant
How are SMAs suitable for dental braces?
Can be designed to change at body temperature; when the braces are placed in the mouth, the wire maintains a constant tension
Exam tip - Answer structure (4)
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
