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Material Science

Smart materials

  • 3 things to know
  • AS 5

Overview

Shape-memory alloys in stents and staples, piezoelectric materials, quantum tunnelling composites, thermochromic, photochromic and electroluminescent materials, and choosing a smart material.

What you need to know

Answer each one before you reveal it.

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Key term

What is a smart material?

Key term

What are the defining features of a shape-memory alloy?

Key term

How is a shape-memory alloy used in a self-expanding stent?

Questions from this subtopic

Each one with the model answer underneath.

  1. 1

    What is a smart material?

    Model answer

    A smart material has one or more properties that change significantly in response to an external stimulus. The change is reversible and can be triggered by temperature, light, stress or voltage.

  2. 2

    What are the defining features of a shape-memory alloy?

    Model answer

    A shape-memory alloy can be deformed when cool and returns to its original shape when heated above a transition temperature. Nitinol, an alloy of nickel and titanium, is the commonest example.

  3. 3

    How is a shape-memory alloy used in a self-expanding stent?

    Model answer

    The nitinol stent is compressed and delivered through a narrow catheter into a blocked artery. Body warmth makes the stent expand to its remembered shape, holding the artery open.

  4. 4

    What are the defining features of a piezoelectric material?

    Model answer

    A piezoelectric material produces a potential difference when it is squeezed or bent. The material also changes shape slightly when a potential difference is applied.

  5. 5

    Give three uses of piezoelectric materials.

    Model answer

    Piezoelectric crystals produce the spark in gas lighters and detect pressure in sensors. Piezoelectric materials also generate and receive ultrasound in medical scanners.

  6. 6

    What are the defining features of a quantum tunnelling composite?

    Model answer

    A quantum tunnelling composite contains metal particles dispersed in an insulating polymer. The composite insulates when relaxed but conducts when compressed.

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