Fluctuations induced transition of localization of granular objects caused by degrees of crowding

Highlights: • Confined large and multiple small granular particles are studied under vibration. • At higher densities, large particles shift from cavity boundary to cavity interior. • This universal behavior is induced by the size disparity of the mixture. • A simple entropic model is developed to elucidate experimental observations. Fluctuations are ubiquitous in both microscopic and macroscopic systems, and an investigation of confined particles under fluctuations is relevant to how living cells on the earth maintain their lives. Inspired by biological cells, we conduct the experiment through a very simple fluctuating system containing one or several large spherical granular particles and multiple smaller ones confined on a cylindrical dish under vertical vibration. We find a universal behavior that large particles preferentially locate in cavity interior due to the fact that large particles are depleted from the cavity wall by small spheres under vertical vibration in the actual experiment. This universal behavior can be understood from the standpoint of entropy.