Robotic swimmer/pump based on an optimal wave generating mechanism

This paper describes a unique mechanism that generates longitudinally traveling waves as a means for fluid manipulation i.e., self-propulsion or pumping in low Reynolds number environments. Possible applications include small-scale micro-robotic swimmers or large-scale pumps for highly viscous fluids. The proposed mechanism generates axi-symmetrical transverse traveling waves along a cylindrical elastic membrane, and it is designed so that the required internal actuation torque on the input shaft is zero in the absence of friction. The paper also demonstrates that torque oscillations can be completely eliminated, even when motional friction exists and only a small constant torque is required to overcome friction. Since torque oscillations are associated with alternating stresses and fatigue, the proposed design increases the service life of the device and, moreover, considerably reduces the power consumption. It is demonstrated analytically and numerically that these properties are achieved by choosing a specific spatial rotational phase between successive cams, and by choosing a certain ratio between the number of wavelengths and cams along the device. A realistic macro-scale device that can be tuned to fulfil the optimal conditions is also described.