A strange property discovered by scientists in rice turns it into a smart material

(Illustrative image of rice research)

This property helps scientists develop a new material that can be used in "flexible" robots.

Rice behaves unexpectedly under pressure. When compressed quickly, it weakens, while remaining strong under slow pressure. This property helps scientists develop a new material that can be used in "flexible" robots that automatically adjust their stiffness, as well as in protective equipment that responds to the speed of an impact.

According to SciTechDaily, citing the journal Matter, using this property, an international team led by the University of Birmingham created a new type of "meta-material," a structure engineered to exhibit behaviors not found in natural materials.

The researchers found that tightly packed rice grains respond very differently depending on the speed at which a force is applied. At high speeds, the material weakens through a process known as "velocity softening," a process not commonly seen in most materials. This occurs because the friction between grains decreases significantly with increasing speed, disrupting the internal force networks that normally bear the load.

Rice is a symbolic material.

A smart granular material.

To take advantage of this phenomenon, the research team combined rice grains with other materials, such as sand, which increase in strength under rapid loads. The result is a composite granular material capable of bending, warping, or stiffening depending on whether forces are applied gradually or suddenly, without the need for electronics, sensors, or automated control.

"Rice may be universally known as a staple food, but it is rarely associated with advanced engineering," says Dr. Mingchao Liu of the University of Birmingham. "The results of this study show that it could form the basis of a new class of functional materials."

Dr. Liu adds, “Instead of treating this phenomenon as an anomaly, we turned it into a design principle. This approach helped create a material that can bend, warp, or stiffen differently when subjected to slow movements compared to sudden impacts, without the need for electronics, sensors, or automated controls. Instead of dictating how the structure should respond, we let the laws of physics dictate that fast loads induce one behavior, and slow loads induce another.”

Advanced Systems

The study’s findings highlight how ordinary granular materials can be engineered into intelligently responsive systems based on their inherent mechanical properties. 

These super-speed-sensitive materials could lead to new developments in flexible robotics, enabling the creation of lighter, safer, and more adaptable machines than traditional metal designs. 

Such robots could work more efficiently alongside humans, operate in harsh environments, or perform delicate tasks like assisting in surgical procedures.

Because this material requires no electronics, power, or sensors, it could also be used in protective equipment that reacts instantly to impact speed. It is able to absorb energy or deform in a controlled manner under the influence of a sudden force, which helps to reduce the risk of injury.