Smart materials

Smart materials

1. most material classifications based on what mat is made form

2. based on properties of the material

   • A smart material has a property that changes when its environment changes
     • which is reversible when the environment changes back to what it was
     • different environmental changes
       • temp
       • pressure
       • light
     • property changed depends on the material
       • colour
       • shape
       • conductivity
     • however most smart materials react to only one feature of the environment, and so one property will cahnge

3. thermochromic pigment

   • the heat from your hand, warms the paint, and it changes colour (with heat)
     • the paint will fade to its original colour when the pigment starts to cool down

4. Shape Memory Alloy

   • metal and a smart material
     • nitinol
     • when a metal is bent to more its elastic limit- its shape is changed
       • for a normal metal, this change is permanent unless you physically bend it back
         • for a smart memory alloy if the metal is heated above a certain temperature it will spring back to its original shape
           • this temperature is called its
             • transition temperature
               • it can often be reached by placing the object made from a shape memory alloy in a bowl of hot water
   • can be used to allow quick repair of damaged products
     • eg bent glasses can ke heated to above transition temp, and will spring back into shape
       • 'memoflex' spectacles
   • movement needed from an electrical signal
     • passing an electric current through a wire spring say, can heat it up above its transition temperature
       • making it return form being stretched out, to coiled up
         • moving whatever the end is attached to
           • this principle can be used to make electrical door locks and artificial muscles in robotic arms