Apr 4, 2014
Boron nitride can harvest mechanical vibrations at the nanoscale
Converting mechanical vibrations into electrical energy is an old problem: all you need is something that vibrates and some kind of transducer to transform kinetic energy into electricity. This is very appealing because mechanical vibrations are an inherently volatile, yet mostly freely available, form of energy. After harvesting, they can be stored as electrical energy or used on the run to power remote and difficult-to-access small devices. Now, reporting in Nanotechnology, researchers may have overcome the challenge of downscaling this to the nanoscale while remaining efficient.
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.
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.
About the author
Riccardo Rurali is a tenured scientist at the Institut de Ciència de Materials de Barcelona (ICMAB-CSIC) in the department of Theory and Simulation of Materials. His research focuses on the theoretical modelling of reduced dimensionality systems, such as semiconducting nanowires and 2D materials.