Mechanical-spring model on ZnO submicron rods for a steady response on vertically integrated nanogenerators at multiple harvesting frequencies

Abstract We have studied the uniaxial compression of ZnO submicron rods grown hydrothermally over Si/Cr/Au and Si/Al substrates such as mechanical springs. We used FEM simulations to find the oscillation frequency range at which the submicron rods deliver the steadiest piezopotential independently of the frequency they oscillate. A stationary and a harmonic spring-mass model were implemented for a single and multiple submicron rods. We measured dimensions and submicron rods/μm2 with our SEM/FIB image analysis. Nanoindentation was used to extract the spring constant and the Young's Modulus of the submicron rods. The steadiest piezopotentials (±3.72, ±5.16 μV) were obtained below 500 kHz. The methodology described can be helpful to design multi-frequency nanogerators.