Advanced Topic 1042 of 1102 Biochemistry, Environment & Industry

Smart Materials

Materials that respond to stimuli such as shape-memory alloys.

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In-depth explanation of Smart Materials

Smart materials change one of their properties in response to an external stimulus such as temperature, light, electric field, magnetic field or stress. Shape memory alloys, such as nitinol, return to a previous shape when heated because of a reversible martensite to austenite phase transformation. Piezoelectric materials such as quartz generate a voltage under stress and deform when a voltage is applied. Thermochromic, photochromic and electrochromic materials change colour, while hydrogels and self-healing polymers respond to moisture or damage. These materials are used in sensors, actuators and medical devices.

Going deeper: Smart Materials

Key ideas: Respond reversibly to a stimulus. Shape memory alloys (nitinol, nickel and titanium) revert by a phase change between martensite and austenite on heating. Piezoelectrics make voltage under stress (quartz). Photochromic glass darkens in UV via silver halide. Thermochromic, electrochromic and self-healing polymers are other types, as are hydrogels responding to pH.

Common mistakes and connections: Mistake: calling any advanced material smart; the key is a reversible, repeatable response to an external trigger. Nitinol recovers about 8 percent strain. Responses are limited in speed and fatigue life. Links to crystal structure, nanochemistry and biomaterials.

Visualization of Smart Materials

Nitinol transforms from martensite to austenite when heated because the entropy gain makes the free energy change negative above a transition temperature near room temperature. The interactive lesson shows this as a live animation or chart.

Worked example and use case

Photochromic lenses darken in bright sunlight because the dye molecules change structure when exposed to UV light.

Frequently asked questions about Smart Materials

What is Smart Materials?

Materials that respond to stimuli such as shape-memory alloys.

Is Smart Materials a beginner, intermediate or advanced topic?

Smart Materials is a advanced topic in Biochemistry, Environment & Industry. It builds on beginner and intermediate topics, so review those first if needed.

What should I learn before Smart Materials?

Study these earlier topics in Biochemistry, Environment & Industry first: Plastic Recycling, Microplastics, Composite Materials.

What comes after Smart Materials?

The next topics in Biochemistry, Environment & Industry are Biomaterials and Atmospheric Composition.

Can I practise Smart Materials with quizzes?

Yes. The interactive lesson includes a self-check question on Smart Materials, and the Biochemistry, Environment & Industry quiz draws on every topic in this area.

Where Smart Materials fits in Biochemistry, Environment & Industry

Smart Materials is topic 67 of 127 in Biochemistry, Environment & Industry.