Measuring Particle Diffusion with the Countoscope

Measuring Particle Diffusion with the CountoscopeA new method for studying the behavior of multiparticle systems relies on a simple "head count" of particles in imaginary boxes. By Michael SchirberO ne way to characterize the interactions in a bacterial colony or a polymer mixture is to trace the path of individual particles through the system, but such tracking can become difficult when the particles are indistinguishable.Researchers have developed a new method that extracts particle dynamics from a simple counting of particles in imaginary boxes of adjustable size [1].They demonstrated this "countoscope" strategy in experiments with small plastic spheres moving around in a liquid.The measured rate of diffusion was different for different sized boxes, which revealed particle clumping.The countoscope's ability to identify such collective behavior could one day help researchers understand the mechanisms that cause bacteria and other life forms to group together.Ball counts.Scientists often characterize interactions among microscopic particles, such as cells or polymers, by tracking individual particles in a large group.A new method takes a different approach in simply counting how many particles are in an imaginary box.The size of the box can be varied to study dynamics at different scales.