Smart materials: The next generation in science and engineering

In recent years, fascinating developments in various areas of materials science have happened. Smart materials, also known as intelligent or stimuli-responsive materials, have attracted attention in science and engineering. Smart materials are divided into six different groups: shape memory materials, piezoelectric materials, magnetostrictive materials, electro-rheological and magneto-rheological fluids, and self-healing materials. Shape-memory and self-healing materials are the most popular and important kinds of smart materials. Shape-memory materials have the ability to react to certain stimuli, such as temperature, pH, light, magnetic fields, and electric fields, and transform from a temporary shape to their original shape after exposure to these stimuli. Shape-memory alloys and shape-memory polymers have attracted the most attention and are widely used among all kinds of shape-memory materials developed. The two most important properties of shape-memory alloys are shape memory and superelasticity. Shape-memory polymers are gaining popularity because of specific benefits such as their high shape recovery rate, light weight, low density, high strength-to-weight ratio, high shape deformability, and readily tailorable glass transition temperature. Self-healing materials have the ability to fully or partially repair their features and functionality after repeated damage. Self-healing materials are divided into two categories: intrinsic and extrinsic, as well as autonomous and non-autonomous. These materials have the potential to increase their lifetime while reducing maintenance costs. Smart materials have a wide range of applications, including aerospace, automotive, biomedicine, and construction. The goal of this paper is to provide an overview of smart materials.