A photoelectrochemical method for determining the kinematics of moving particles using an array of individually addressable electrodes

We present the novel use of photoelectrochemistry to detect and monitor the trajectory of moving spheres. Using an array of individually addressable electrodes under illumination and potentiostatted so that a photocurrent is generated, the motion of a sphere is detected by means of measuring "dark" transients as the shadow cast by the moving sphere passes over each electrode. The method can used to determine the size and velocity of a single ball, or simultaneously track two spheres in collision.