A Membrane Magnetoelastic Generator for Acoustic Energy Harvesting

Acoustic waves are a type of energy propagation through a medium with a low energy density, which makes it challenging to be converted into electricity. Here, a membrane magnetoelastic generator is presented as a fundamentally new technology for acoustic energy harvesting that is centered on a coupling of magnetoelastic effect and electromagnetic induction. It is as thin as 400 µm, holds a skin-alike modulus of 2.59 × 10⁷ Pa, a low internal impedance of 137 Ω, and a high current density of 107 mA m⁻² at a sound pressure level (SPL) of 95 dB. It can efficiently harvest acoustic energy to charge a 47 µF commercial capacitor to 2 V in 20 s. With an all-in-one-body design, the membrane magnetoelastic generator shows stable electrical output against environmental moisture and particulates. Toward practical application, it is demonstrated to harvest acoustic energy from a vehicle stereo and use recycled energy to charge a smartphone. Its inherent water-/dust-proof features open new possibilities for acoustic energy harvesting from city buildings, highways, airplanes, and even battlefields.