A self-propelled device for locomotion through a lumen, comprising a set of serially arranged inflatable chambers, adjacent chambers being fluidly connected, and a fluid source attached to one end of the set, such that the chambers inflate sequentially. The chambers are constructed of an elastic material and have a wall thickness and dimensions such that they have a characteristic with a non-monotonous relationship between the inflation pressure within the chamber and the chambers inflated size. The characteristic is such that after an initial inflation pressure peak, the non-monotonous relationship adopts a negative slope, such that the volume of the chamber increases more rapidly than the volume of fluid flowing into it, and the inflation pressure of the chamber falls. This effect causes the chamber to inflate and anchor rapidly, while essentially slowing down the inflation of the succeeding chamber until inflation of the first is complete.
