Drag-out of bubbles by a plate withdrawn from a liquid bath

We report work on a new aspect of the classic Landau--Levich problem of liquid drag-out by a moving plate, namely, interaction of bubbles with the coating flow. Due to the cheerios effect, bubbles present in a liquid bath may gather at menisci such as those caused by a partially-submerged plate. Our experiments show that a critical withdrawal speed exists. Below this speed, bubbles are in stable equilibrium and remain stationary in the lab frame as the plate is withdrawn. Above the critical speed, no stable equilibrium exists and bubbles are drawn up onto the plate, with obvious consequences for the uniformity of the resulting coating. We examine the dependence of the critical speed on fluid properties.