Beam-Based Vibration Energy Harvesters Tunable Through Folding

We present a novel beam-based vibration energy harvester, and use a structural tailoring concept to tune its natural frequencies. Using a solution of the Euler–Bernoulli beam theory equations, verified with finite element (FE) solutions of shell theory equations, we show that introducing folds or creases along the span of a slender beam, varying the fold angle at a crease, and changing the crease location helps tune the beam natural frequencies to match an external excitation frequency and maximize the energy harvested. For a beam clamped at both ends, the first frequency can be increased by 175% with a single fold. With two folds, selective frequencies can be tuned, leaving others unchanged. The number of folds, their locations, and the fold angles act as tuning parameters that provide high sensitivity and controllability of the frequency response of the harvester. The analytical model can be used to quickly optimize designs with multiple folds for anticipated external frequencies.