This disclosure concerns medical devices, such as catheters and implantable devices, having radially adjustable features. More particularly, the catheters and implantable devices can radially expand and contract to perform various functions within the body. Expansion and contraction can be performed by a radially adjustable structure mounted on the medical device. For example, a medical device can include an body configured for in vivo introduction, a strip attached to the body and rolled into a ring such that layers of the strip radially overlap each other, and at least one motor actuatable by electrical energy to move the radially overlapping layers of the strip relative to one another and change a diameter of the ring and the body.
