A device for applying a bubble of a substance to a tissue surface, the device comprising a cannula, a distal tip at the distal end portion of the cannula, the distal tip having a bubble support surface and an exit port extending through the bubble support surface, an expansion fluid passageway extending through the cannula to the exit port, a source of an expansion fluid and an actuator therefor. In some arrangements, the distal tip can be configured to support a layer of the substance thereon over the distal port and the device can be configured such that the advancement of the expansion fluid from the fluid source through the exit port causes at least one bubble of the substance to form on the distal tip, wherein the at least a portion of the bubble can be transferred to the tissue surface to treat a defect on the tissue surface.