Study Uncovers Unique Behavior of Rice Grains Under Pressure
Published on June 11, a new study reveals how densely packed rice grains respond to pressure in a way that depends entirely on how fast the force is applied. When compressed slowly, the material becomes stronger, but a sudden, high-speed impact actually weakens it due to a drop in friction between the grains.
Experiments showed that tightly packed rice grains exhibit a remarkable reaction to applied force. The key factor is the speed of that force: slow compression helps the grains hold their shape and maintain strength, while a rapid strike causes the material to lose stability. This effect is known as speed-dependent friction reduction, where the friction between individual rice grains plummets, and the internal force chains that normally bear the load collapse almost instantly.
Developing a New Metamaterial
Using these findings, engineers combined rice-based granular particles with other materials like sand to create a unique composite metamaterial. This new substance can bend, deform, or harden on its own depending on the situation—without needing any microchips, sensors, or batteries.
Dr. Mingchao Liu of the University of Birmingham explains: 'Instead of programming the structure electronically, we let the laws of physics make the decisions for the device: fast loads trigger one type of material behavior, while slow loads trigger a completely different one.'
This breakthrough opens up possibilities for soft robotics, medicine, and complex surgical procedures. The rice-based metamaterial is also ideal for making sports and military protective gear, highlighting its potential across a wide range of applications.
The research and development of this rice-grain metamaterial underscore how fundamental physical properties of materials can drive new technologies. Using natural substances like rice could pave the way for innovations in fields such as medicine and engineering. Further studies may lead to new uses in protective gear and adaptive systems that respond to changing loads without any electronic components.