Simple millimeter-scale robot using Pb(Zr, Ti) piezoelectric thin film actuator on titanium substrate

We have developed a piezoelectric-driven millimeter-scale robot with a simple structure. This millimeter-scale robot, which consists of a titanium (Ti) body and front/back legs integrated with a Pb(Zr, Ti)O3 (PZT) piezoelectric thin film actuator, is driven by using mechanical resonance. To simply fabricate the millimeter-scale robot, the PZT thin film was directly deposited on an H-shaped Ti substrate by radio frequency magnetron sputtering and the shape of the robot was completed by plastic deformation of the monolithic Ti substrate. We obtained the transverse piezoelectric coefficient d31 of the deposited PZT thin film was ?21.3 pm/V, which was sufficient for driving the fabricated millimeter-scale robot with a low driving voltage ≤10 V. We also evaluated the resonant characteristics of the fabricated robot and confirmed that the front/back legs of robot were oscillated in primary and secondary resonance modes at around 4.5 and 11 kHz, respectively. We demonstrated that the millimeter-scale robot with asymmetric structure in the front-back direction was controlled by changing driving voltage conditions and a bending angle formed by the front/back legs. The moving speed of the millimeter-scale robot was 13.6 cm/s by applying negative unipolar voltage of 10 Vpp at 10.6 kHz when the bending angle was set to 109°. We experimentally confirmed that the millimeter-scale robot can be driven forward and backward by optimizing the shape of the robot and mechanical resonant modes.