Smart materials are materials that are manipulated to respond in a controllable and reversible way, modifying some of their properties as a result of external stimuli such as certain mechanical stress or a certain temperature, among others. Because of their responsiveness, smart materials are also known as responsive materials. These are usually translated as "active" materials although it would be more accurate to say "reactive" materials. [1]

Figure 1. Types of Smart material technology

Figure 1 shows A smart material is an object that holds a property that is susceptible to change with the introduction of an external stimulus. This change must be either tangible or visible for the material to qualify for ‘smart’ status. These changes can include:

• Electrical
• Chemical
• Thermal
• Mechanical
• Magnetic

The definition of smart materials has been expanded recently to include any materials that may not display a physical change, but do hold electronic functionality. [2]

Types of Smart Materials

Piezoelectrics:

Piezoelectric materials convert electrical energy to mechanical energy, and vice versa. They offer a wide range of utility and can be used as actuators (provide a voltage to create motion), sensors, such as many accelerometers, and energy harvesters since the charge generated from motion can be harvested and stored. Common applications for piezo materials are BBQ igniters and actuators for inkjet printer heads. Midé has successfully commercialized energy harvesters, haptic actuators, piezo valve actuators, and flow control devices.

Magnetostrictive:

Similar to piezoelectric materials that respond to changes in electrical fields, this class of materials responds to changes in magnetic fields and can perform as an actuator, or sensor if deformed. While they can work well, they exhibit a large hysteresis which must be compensated when using the material in sensor applications.

Shape Memory Polymers:

Shape Memory Polymers (SMP) are similar to Shape Memory Alloys except the obvious fact they are made from a polymer matrix. They possess much greater recoverable strains than the alloys, but typically under lower forces. Morphing structures has been the area of greatest use to date for SMP’s.

Electroactive Polymers:

There are many forms of electroactive polymers and many are still being refined. They have great potential as the flexibility of how they can be used provide advantages over some of the metals and ceramics mentioned above. Most typically applications include energy harvesting and sensing (see Stretchsense development kit) however some researchers are looking at high voltage, low current actuators.

Bi-Component Fibers:

Adaptive thermal insulation can enable smart clothing that can change its thermal properties based on the environment. Midé has developed bi-component fiber technology where two different materials are co-extruded together to enable shape change depending on ambient temperature.

References:

1. https://www.iberdrola.com/innovation/smart-materials-applications-examples
2. https://www.engineerlive.com/content/what-smart-material
3. https://www.mide.com/smart-materials

Cite this article:

Thanusri swetha J (2021), Types of Smart Material Technology, Anatechmaz, pp. 77