Figure 1. (a) Schematic of a conventional bistable energy harvester (BEH). (b) Schematic of two-degree-of- freedom magnetically coupled bistable energy harvester (2-DOF MCBEH). In (a) , one bimorph beam with a tip magnet oscillates, and another magnet is attached to the rigid base structure. In (b) , two bimorph beams with tip magnets oscillate. As a representative, the out-of-phase motion is illustrated. The red and blue areas of the magnets indicate the N-pole and the S-pole, respectively. The harmonic base excitation is formulated by f b cos (� t ) . w 1 and w 2 are the deflections of the beams at the tips with respect to the neutral surface. Voltage outputs across the load resistances are denoted by V 1 and V 2 . Gravitational force acts in the direction of the y -axis.