Smart material

Smart materials, also called intelligent or responsive materials, are designed materials that have one or more properties that can be significantly changed in a controlled fashion by external stimuli, such as stress, moisture, electric or magnetic fields, light, temperature, pH, or chemical compounds. Smart materials are the basis of many applications, including sensors and actuators, or artificial muscles, particularly as electroactive polymers (EAPs). Terms used to describe smart materials include shape memory material (SMM) and shape memory technology (SMT). There are a number of types of smart material, of which are already common. Some examples are as following: Piezoelectric materials are materials that produce a voltage when stress is applied. Since this effect also applies in a reverse manner, a voltage across the sample will produce stress within sample. Suitably designed structures made from these materials can, therefore, be made that bend, expand or contract when a voltage is applied. Shape-memory alloys and shape-memory polymers are materials in which large deformation can be induced and recovered through temperature changes or stress changes (pseudoelasticity). The shape memory effect results due to respectively martensitic phase change and induced elasticity at higher temperatures. Photovoltaic materials or optoelectronics convert light to electrical current. Electroactive polymers (EAPs) change their volume by voltage or electric fields. Magnetostrictive materials exhibit a change in shape under the influence of magnetic field and also exhibit a change in their magnetization under the influence of mechanical stress. Magnetic shape memory alloys are materials that change their shape in response to a significant change in the magnetic field. Smart inorganic polymers showing tunable and responsive properties. pH-sensitive polymers are materials that change in volume when the pH of the surrounding medium changes. Temperature-responsive polymers are materials which undergo changes upon temperature.