2.8 ~ Performance characteristics of smart materials

Define smart material

Materials whose physical properties change in response to an input or change in environment, such as electricity, pressure, temperature or light

Shape memory alloy (SMA )

SMAs such as nitinol change shape in response to changes in temperature or electrical input. Once heated to a certain temp (transition temp), it will return to its original shape

Examples of smart materials

SMA (nitinol)Thermochromic pigment Phosphorescent pigment Photochromic pigment Electroluminescent wire Piezoelectric material

How do SMAs (e.g. nitinol) work?

Changes shape in response to a change in temperature or electrical input; e.g nitinol wire in a dental brace changes length in response to a change in temp

SMAs (e.g. nitinol) uses

Dental braces, self-closing windows, aeroplane wing flaps, bioengineering such as stents, bone plates and screws

How does thermochromic pigment work?

Changes colour in response to temperature change

Thermochromic pigment uses

Room thermometers, medical thermometers for children, bath water thermometers, colour-changing mugs and kettles, food packaging to indicate food is hot to eat 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 energy when it is dark

Phosphorescent pigment uses

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

Photochromic pigment uses

Welding goggles, reactive spectacle lenses, security markers that show up under UV light

How does electroluminescent wire work?

Thin copper wire coated in a phosphorescent material that glows in response to an alternating current

Electroluminescent wire uses: glow brace; interweaving for clothing; home decoration; outdoor decorative lighting

How does piezoelectric material work?

Gives off a small electrical charge when deformed. Increases in size (up to 4%) when an electrical current is passed through it

Piezoelectric material uses: Airbag sensors in cars, lighters for barbecues, vibration damping in tennis racquets, Musical greetings cards, pressure sensors