Fig. 3: Characterizations of output displacement of PHRI.

a Output displacement at various driving voltages. b PHRI with different output deformation sizes. c Output displacement of different output deformation sizes. d–h Output displacements at different frequency driving voltages with via hole diameters of d 0.4, e 0.6, f 0.8, g 1.0, and h 1.2 mm. i Comparison of peak-to-peak output displacement for different via hole diameters at different frequency driving voltages