What are smart and modern materials, and how do their responsive properties enable new products?
Smart materials that respond to a change in their environment (shape memory alloys, thermochromic and photochromic pigments, quantum tunnelling composite, electroluminescent and piezoelectric materials) and modern materials developed through new processes.
A focused answer to WJEC A-Level Design and Technology Unit 3 smart and modern materials, covering materials that respond to their environment (shape memory alloys, thermochromic and photochromic pigments, quantum tunnelling composite, piezoelectric and electroluminescent materials) and modern materials such as precious metal clay and polymorph.
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What this dot point is asking
WJEC wants you to define a smart material, distinguish it from a modern material, and explain how named examples respond to a stimulus to improve a product. The exam reliably asks for a definition plus a worked product example, and the higher-mark questions ask you to discuss two materials and the functional benefit each brings. You need the stimulus, the response, and a real use for each material.
The answer
What makes a material "smart"
The contrast is with a passive material, which simply sits there. A smart material does something in response to its surroundings, which is why it can replace electronics or moving parts.
Key smart materials
- Shape memory alloy (SMA) - for example Nitinol. Deformed cold, it springs back to its set shape when heated past a transition temperature. Uses: flexible spectacle frames, self-expanding medical stents, thermostatic actuators.
- Thermochromic pigment - changes colour with temperature. Uses: kettle and baby-bottle hot-warnings, mood toys, battery test strips, novelty mugs.
- Photochromic pigment - darkens in ultraviolet light and clears indoors. Uses: reactive sunglasses lenses, security marking.
- Quantum tunnelling composite (QTC) - an insulator that conducts when compressed. Uses: pressure-sensitive switches, membrane controls, robotic touch sensing.
- Piezoelectric material - produces a voltage when stressed and flexes when a voltage is applied. Uses: gas igniters, microphones, impact and vibration sensors, fine actuators.
- Electroluminescent (EL) material - glows when a voltage is applied. Uses: flexible safety lighting, backlights, decorative EL wire.
Modern materials
Modern materials matter because they let designers do things that were not previously possible, such as model directly in a mouldable polymer or use a renewable bioplastic.
Examples in context
Example 1. A camping gas lighter. Squeezing the trigger stresses a piezoelectric crystal, generating a high voltage that jumps as a spark to ignite the gas, with no battery or flint. The whole product works on one smart-material effect.
Example 2. Reactive sunglasses. Photochromic pigment in the lens darkens in ultraviolet light outdoors and clears indoors, so one pair adapts to the conditions automatically, a function impossible with an ordinary tinted lens.
Try this
Q1. State the stimulus and the response for a shape memory alloy. [2 marks]
- Cue. Stimulus: heating above its transition temperature; response: returns to its pre-set remembered shape.
Q2. Give one product use of quantum tunnelling composite and explain why the material suits it. [2 marks]
- Cue. A pressure-sensitive switch or touch sensor; QTC changes from an insulator to a conductor when compressed, so pressure alone closes the circuit with no moving contacts.
Exam-style practice questions
Practice questions written in the style of WJEC exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
WJEC 20194 marksExplain what is meant by a smart material and describe one use of a shape memory alloy in a product.Show worked answer →
A smart material is one whose properties change in a controlled, reversible way in response to a change in its environment, such as temperature, light, stress, electric current or pH. The change is the useful function, and it happens without a person operating a mechanism.
A shape memory alloy (SMA), such as Nitinol (a nickel-titanium alloy), returns to a pre-set shape when heated above a transition temperature, even after being deformed cold. A common product use is in spectacle frames, where the SMA arms spring back to shape after being bent, so the glasses resist damage. Other uses include medical stents that expand at body temperature and thermostatic actuators.
Markers reward the definition (reversible property change in response to an environmental stimulus) and a correct, specific SMA product use with the mechanism (returns to its remembered shape on heating).
WJEC 20216 marksDiscuss how smart materials can improve the function of products, using two named examples.Show worked answer →
A good answer names two distinct smart materials and links each to an improved function.
Thermochromic pigment changes colour with temperature. Built into a kettle, baby bottle or battery test strip, it gives an instant visual warning that a surface is hot or a battery is charged, improving safety and usability with no extra electronics or moving parts.
Piezoelectric material generates a small voltage when stressed (and deforms when a voltage is applied). Used in a gas igniter, a striking action stresses the crystal and produces a spark, removing the need for matches; the same effect senses vibration in microphones and impact sensors.
A second strong pairing is a shape memory alloy for self-resetting frames or expanding medical stents, and electroluminescent wire for flexible low-power lighting. Markers reward two correct materials, the stimulus and response of each, and a clear functional benefit (safety, simplicity, new capability).
Related dot points
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A focused answer to WJEC A-Level Design and Technology Unit 3 composite materials and technical textiles, covering how composites combine a matrix and reinforcement (GRP, carbon fibre reinforced polymer, concrete, plywood) and how technical or performance textiles such as Gore-Tex, Kevlar and conductive fabrics are engineered for specific functions.
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A focused answer to WJEC A-Level Design and Technology Unit 3 electronic systems and programmable components, covering the input-process-output systems model, common input sensors and output devices, and how programmable microcontrollers make products more functional, flexible and reprogrammable.
- Classification of papers and boards, timbers, metals, polymers and textiles into families, and the criteria used to select a material for a given product and context.
A focused answer to WJEC A-Level Design and Technology Unit 1 classification and selection of materials, covering the main material families (papers and boards, timbers, metals, polymers and textiles), how each splits into sub-groups, and the criteria used to justify a material choice for a product.
- Physical and mechanical working properties of materials - strength, hardness, toughness, ductility, malleability, elasticity, plasticity, density, durability, electrical and thermal conductivity - and how they govern selection and processing.
A focused answer to WJEC A-Level Design and Technology Unit 1 working properties of materials, covering the physical properties (density, conductivity, durability) and mechanical properties (strength, hardness, toughness, ductility, malleability, elasticity, plasticity) and how each affects material selection and processing.
Sources & how we know this
- WJEC AS/A Level Design and Technology specification — WJEC (2017)