To characterize sliding behavior of water droplets with dynamic contact angles on hydrophobic, the instrument was developed. Sliding action of the droplet was classified into three motion categories: constant accelerated motion, constant velocity and stasis. The action of the sliding droplet was controlled by the interaction between solid and liquid surface. This interaction was expressed by the internal fluidity of the sliding droplet. The device with PIV facilitated the measurement of the sliding acceleration, shape variation and internal fluidity in the sliding droplet.
