Granular materials made from soft inflatable particles

The mechanical behavior of granular materials emerges from the interplay between particle configurations and interparticle interactions. Properties such as rigidity and mechanical moduli can vary dramatically with particle friction, deformability, and packing configurations. To understand and control these behaviors, we have developed a 2D robotic granular platform in which the size of individual soft particles is tuned through internal pressure control. This setup allows us to continuously vary the packing fraction and particle interactions while directly measuring its mechanical response. Through these experiments, we identify a continuous rigidity transition that depends on particle size, deformation, and frictional interactions. By enabling control at the single-particle level, this system provides a pathway to design granular packings with predictable, tunable properties and opens new directions toward trainable granular metamaterials that adapt through local feedback.