In everyday life, we use objects that possess specific properties enabling them to perform certain functions. For example, the softness of a pillow provides comfort, while the rigidity of a rolling pin enables even rolling. Once made, these objects cannot change their properties. A pillow will never become a rolling pin, nor will a rolling pin provide the comfort of a pillow.

But imagine an object that can change its properties from soft to rigid with a simple move. Such an object could be as soft as a pillow at one moment and as rigid as a rolling pin at another. This multifunctionality could significantly reduce the need for different resources, bringing a revolution to the sustainability of everyday technologies.

Advancement in Materials
My team and I are exploring reconfigurable mechanical metamaterials, which represent a new class of materials with adaptable internal structure. These materials have the unique ability to switch between three antagonistic states: floppy, rigid, and multistable. This means their properties can be altered as needed, allowing the material to be hard or soft, or even retain energy.

An object made from these metamaterials can become rigid to withstand external forces, adapt its shape like a floppy mechanism, or absorb energy like a multistable material. This capability makes it extremely useful for various applications.

Post-production Adaptation
A key component of these materials is the meta-joint that enables property change after fabrication. The change occurs by applying forces to specific points where edges join, forming a flexible joint. In one state, the block is rigid because the joint is not activated, while in another state, joint activation enables local rotation, making it flexible.

This reconfigurable block can be used to create structures with adaptable properties. For example, a beam can be rigid or flexible depending on the applied load. Additionally, blocks can be assembled in two dimensions to create different configurations, each with its characteristics: rigid, floppy, or multistable.

Practical Applications
These multifunctional materials can be applied in various sectors. Besides physical properties, geometric properties can also be adjusted. For instance, by reprogramming units, product size and shape can be changed.

One example is a multifunctional clothes hanger. By selectively activating joints, the hanger can fold to save space or expand to accommodate clothes of various sizes. This level of adaptability leads to more sustainable resource use.

An all-in-one class of metamaterials helps in creating multi-purpose products. The multifunctionality promises resource reduction, opens a sustainable path for future technologies, and contributes to achieving sustainability goals, thereby creating a greener and more resilient future.

Original:
Damiano Pasini
Professor of Mechanics and Materials at McGill University