Table 3.

Comparison of some non-resonant devices. Bistable devices can be benchmarked based on the bistability mechanism. Magnetic repulsion/attraction devices show large bandwidths, but the use of magnets limits technological scaling (magnetic attraction devices require double number of magnets than magnetic repulsion-based harvesters). Buckled beam-based harvesters employ a snap-through mechanism, and are better suited for integration. The main drawback of bistable devices is that they require a particular amount of energy to overcome the potential barrier and switch between the two stable states.

Reference	Bistability Mechanism	Advantages	Drawbacks
[96]	Magnetic repulsion	Large bandwidth at low frequencies (0∼100 Hz); MEMS	Input force threshold to achieve bistability; lower response than resonant device at its natural frequency
[105]	Magnetic attraction	High power output at less than 10 Hz	Input force threshold to achieve bistability; lower response than resonant device at its natural frequency; number of magnets
[108]	Clamped-Clamped buckled beam	No hinges, internal stress or magnets required; MEMS	Input force has to exceed the buckling load
[109]	Simply supported buckled beam	No hinges, internal stress or magnets required; improved transduction mechanism	Input force has to exceed the buckling load
[114]	Bio-inspired by auditory system	Snap-through mechanism, independent from excitation frequency; well suited for 1∼10 Hz harvesting	Advanced mechanical structure with a commercial piezoelectric harvester