In some examples, a catheter includes an elongated body and an expandable member at a distal portion of the elongated body and defining at least part of a distal tip of the catheter. The expandable member includes a flexible membrane and an expandable ring or partial ring located at a distal portion of the expandable member, wherein the expandable ring or partial ring is configured to expand radially outward in response to electrical energy applied to the expandable ring or partial ring.