Mechanical-to-electrical energy conversion is conventionally accomplished by coupling a linear mechanical resonator, such as a cantilever, and some kind of piezoelectric transducer. Linear oscillators, however, respond very well at their resonant frequency, but are almost insensitive when moving away from that magic spot. Hence, they are certainly not the best choice when it comes to broad spectral densities, such as those of ambient vibrations.

Broadening response

Here, the team from the Institut de Ciència de Materials de Barcelona, uses monolayered hexagonal boron nitride (h-BN) to harvest mechanical vibrations. They numerically show that, by applying a small compression, the system is driven into a bi-stable regime where the dynamics are described by a double-well potential landscape: if the barrier ΔE has just the right height, high-frequency vibrations in each of the wells combine with the allowed, lower-frequency swings from one minimum to the other; therefore broadening the spectral response function of the system.

An all-in-one solution

Additionally, h-BN is a piezoelectric material itself, so there is no need for a dedicated nanoscale transducer, with all the complex engineering associated: the BN sheet senses and transduces the vibration at once.

More information can be found in the journal Nanotechnology 25 175401.

Further reading

Going beyond the traditional electromagnetic generator (Mar 2014)
Studies of defects in boron nitride reveal useful properties for devices (Jan 2014)