A bi-stable buckled energy harvesting device actuated via torque arms

A bi-stable switching energy harvester made from a buckled steel structure mounted with uniaxially poled piezoelectric polyvinylidene fluoride and 3D printed polylactic acid components is constructed and tested. A data collection system and frequency sweeping program is built to drive the device using a custom compression rig fitted with an accelerometer. The energy harvester is tested with the center beam compressed to different degrees of buckling, as well as in its unloaded state. Root mean square (RMS) accelerations are applied to the device in the range of 0.1–0.9grms by 0.2 g steps. The device is driven with a frequency between 16 and 40 Hz (by 0.5 Hz) in both forwards and backwards sweeps. Finite element modeling program ANSYS is used to model the device and determine undamped pre-stressed modal frequencies, proof mass displacements to ‘snap-through’, and static buckled profiles for the center beam. As a comparison, a doubly constrained beam (DCB) with the same width and length is constructed and tested in the same manner as the torque arm device. RMS power density for the torque actuated device compressed by 0.13 mm and frequency swept in reverse was 0.246 μWcm (3.13 μW) at 16.5 Hz and 1.5grms using two 0.19 g proof masses. The DCB RMS power density swept in reverse was 1.287 μWcm (6.18 μW) at 59.5 Hz and 1.5grms with a 1.38 g proof mass.