In recent years, materials science has played a crucial role in driving groundbreaking developments in the field of technology. Smart materials that undergo changes in their properties due to external stimuli, such as light, heat, or humidity, have provided scientists with new perspectives on advancing high-end technologies. Intensive research has particularly focused on smart materials that can bend, flex, expand, or contract when subjected to external influences, with significant efforts over the past decade.
There are various types of smart materials, among which an intriguing category stands out: shape memory alloys. Shape memory alloys are materials that change shape under the influence of heat but revert to their original shapes when they return to their initial temperatures, hence "remembering" their original forms.
Transitions between the solid, liquid, and gas states of matter are well-known to all of us. However, in shape memory alloys, this change in material properties occurs within the solid-state without a phase transition. This change is attributed to shifts in the positions of atoms within the material's crystalline structure. For example, nitinol, an alloy of nickel and titanium, which was one of the first shape memory alloys discovered, becomes more flexible as its temperature decreases from high levels. This flexibility allows it to change shape when subjected to force. When the material is subsequently heated, the atoms in the nitinol's crystalline structure return to their original positions at high temperatures, restoring the material to its initial shape.
However, shape memory alloys tend to lose this property after undergoing numerous cycles of deformation. In other words, when subjected to external forces, these materials may not fully return to their original shapes. This is believed to be due to molecular-scale damage caused by the applied forces within the material's crystalline structure. For these materials to be widely adopted in technologies, they must retain the ability to return to their original shapes even after multiple shape changes.
In a study published in the May issue of the Science journal, scientists have developed a material composed of nickel, titanium, and copper that can undergo more than 10 million shape changes without sustaining any damage to its crystalline structure.
This breakthrough paves the way for combining the effective properties of smart metals with architectural applications. Integrating these effective properties of smart metals with architecture will open up new possibilities. For instance, in a project like the one we have designed, the use of smart metals in facade design will reduce the substantial energy required for climate control in countries with extremely high daytime temperatures, such as Dubai. This natural climate control will be achieved through the passive mechanical energy of the metals.
We will harness this energy through the responses of hexagonal-shaped metals in our design to changes in temperature. These metals undergo changes in their form based on differences in heat levels. When they reach a certain temperature threshold, they mechanically close, creating a shading effect on the building facade, using the energy obtained from the sun. This will prevent excessive heating of areas exposed to the sun while harmonizing the texture of the facade with open-form metals experiencing different temperature levels in the less sun-exposed areas. As the closed metals mechanically revert to their original form with the night air cooling, the building will take on a new appearance during the night, illuminated by light beams from the nighttime facade.
The use of smart metals in building construction technologies can potentially transform energy-intensive structures like skyscrapers into more eco-friendly buildings in the future.