Rice grains were the basis for an innovative discovery by scientists, who developed a new material capable of changing its behavior depending on the speed of pressure applied. This peculiar characteristic allows the creation of structures that react in different ways to slow movements and sudden impacts, without the use of sensors or electronics.
Despite being essential in the global diet, rice has demonstrated significant potential in materials engineering. Researchers have noticed atypical behavior in grains compacted under different forces, paving the way for advances in the area of smart materials.
The research revealed that rice’s strength varies with compression: it is stronger under gradual pressure, but surprisingly more brittle when compressed quickly. This phenomenon inspired the creation of an innovative material, which promises future applications in flexible robots with self-adjusting rigidity and in safety equipment that adapts to the force of a collision. The work was carried out by an international team, led by the University of Birmingham, and their results were published in the journal Matter.
Uncovering the particularity of rice under different pressures
Studies conducted by the team indicated that the way compacted rice grains react changes drastically depending on the speed of the force applied. In situations of more accelerated loading, a considerable reduction in the material’s resistance was observed.
This behavior, classified as “strain rate softening”, is rare in most compounds. Scientists explained that this phenomenon occurs due to the decrease in friction between rice grains when subjected to rapid forces. This results in the weakening of internal force networks that would normally provide load support. Based on this unique property, the research group was able to develop an unprecedented metamaterial, which is a structure designed to exhibit characteristics that are not found in nature.
The development of a metamaterial capable of self-tuning
To design the new compound, the researchers combined granular units derived from rice with other elements, such as sand, known to become more rigid under accelerated loads. The end result was a granular metamaterial that can react in different ways to slow movements and sudden impacts.
The material can bend, deform or stiffen in different ways, adapting to the situation without requiring electronics, sensors or active control systems. Dr Mingchao Liu from the University of Birmingham commented on the discovery, highlighting that although rice is a global staple, its association with advanced engineering is unusual, but his research demonstrates new potential for functional materials.
He explained that, rather than viewing the phenomenon as a mere curiosity, the team turned it into a design principle. This approach allowed the creation of a material that behaves differently under slow movements and fast impacts, without the need for electronic components. According to Liu, physics decides the reaction, with fast loads triggering one behavior and slow loads another. Scientists say the study highlights the ability to transform common granular materials into systems designed to respond intelligently through their own mechanical properties.
Possible uses of smart material in robots and protective items
Velocity-responsive metamaterial opens new perspectives for flexible robotics. Unlike robots made with traditional metals, future systems built with this type of material could be lighter, safer and adaptable for different functions.
These robots can be especially useful in collaboration with humans, operating in challenging environments, and performing delicate tasks such as assisting in surgical procedures. The material also presents possibilities for application in protective equipment. Due to its ability to react differently depending on the speed of the impact, it can absorb energy or deform in a controlled way during a collision, minimizing the risk of injury. It is crucial to highlight that these responses occur without the need for electronics, external energy or sensors, allowing the material itself to automatically adapt to changing conditions.
