Which term describes materials that respond to external stimuli?

Smart materials are specifically designed to have properties that change in response to environmental conditions or external stimuli, such as changes in temperature, pressure, light, or electric and magnetic fields. These materials can adapt or respond actively to these changes, making them highly versatile for applications in various engineering fields, including aerospace, automotive, and medical technologies.

For instance, thermochromic materials change color at specific temperatures, while piezoelectric materials can generate an electric charge in response to mechanical stress. This unique ability to respond dynamically distinguishes smart materials from other types, emphasizing their role in innovative designs and technologies.

In contrast, composite materials consist of two or more constituent materials with different physical or chemical properties, aimed at achieving enhanced overall performance. Natural materials, derived from living organisms or geological processes, do not inherently possess the ability to respond actively to external stimuli. Conductive materials, while important in electrical applications, refer specifically to materials that allow the flow of electric current but do not imply any active response to changes in their environment. Thus, the term "smart materials" most accurately characterizes materials that react to external stimuli.