Hydroelastic Power and Thrust Generation Using Macro-Fiber Composite Piezoelectrics

Flexible piezoelectrics offer several advantages to use in energy harvesting and biomimetic locomotion. These advantages include ease of application, high power density, silent and effective operation over a range of frequencies as well as light weight. Piezoelectric materials exhibit the well-known direct and converse piezoelectric effects. The direct piezoelectric effect has received growing attention for low-power generation to use in wireless electronic applications while the converse piezoelectric effect constitutes an alternative to replace the conventional actuators used in biomimetic locomotion. In this paper, underwater thrust and electricity generation are investigated experimentally by focusing on biomimetic structures with macro-fiber composite piezoelectrics. Fish-like bimorph configurations with and without a passive caudal fin (tail) are fabricated and compared. The favorable effect of having a passive caudal fin on the frequency bandwidth is reported. The presence of a passive caudal fin is observed to bring the second bending mode close to the first one, yielding a wideband behavior in thrust generation. The same smart fish configuration is tested for underwater piezoelectric power generation in response to harmonic excitation from its head. Hydrodynamic loads resulting from base excitation yield considerably larger power output as compared to in-air base excitation at the same acceleration amplitude. This work also discusses the feasibility of thrust generation using the harvested energy toward enabling self-powered swimmer systems.