Metamaterial-based energy harvesters have emerged as promising alternatives to achieve the low-frequency, broadband energy harvesting since their performance fundamentally depends on the band gap structures, having greater tuning flexibility through their unit cell designs. However, specific strategies to convert the available wave energy into usable forms need to be explored further. Recently, a class of mechanical systems composed of unit cells with multiple stable states has been widely studied for its ability to support topological solitary waves, which can theoretically travel arbitrarily long distance without any dispersion. In particular, lattices with asymmetric bistable onsite potentials have shown an extreme unidirectional propagation \[1\], and it has been further observed that the responses away from the lattice boundaries are invariant and independent of the types of the excitations as long as transition waves can be generated within the lattices \[2\]. Due to the inherent discreteness of the lattice designs, there is always small radiated energy in the form of induced vibration at each unit cell as main transition waves pass by. The observed response invariance applies to these trailing vibrations as well, and the radiated vibrations are always at single dominant frequencies, providing an efficient means to harvest the wave energy through resonant transduction. Furthermore, the input independence enables effective frequency conversion between external inputs and dynamics internal to the lattice, hence suggesting an ideal alternative for achieving broadband energy harvesting.

In this study, we seek to enhance the potential for energy harvesting in such bistable lattices by proportioning the available energy in the system to radiated energy through the induced tail motions. To that end, we introduce inertially and elastically equivalent lattice models that differ only in their lattice discreteness and numerically study its effect on the stability of the transition waves and characteristics of the induced vibrations. We obtain a harvesting capability diagram as a function of the lattice discreteness, followed by experimental validations on 3d-printed demonstrators. We also present an asymptotic analysis on their dispersion relations, which, combined with the response invariance, may contain valuable information about the propagation speed of the main transition wave.

 

References:

\[1\] Nadkarni, N., Arrieta, A. F., Chong, C., Kochmann, D. M. and Daraio, C., “Unidirectional Transition Waves in Bistable Lattices,” Physical Review Letters 116(24), 244501 (2016).

\[2\] Hwang, M. and Arrieta, A. F., “Input-independent Energy Harvesting in Bistable Lattices from Transition Waves,” Scientific Reports 8, 3630 (2018).


Discreteness Effect in Bistable Lattices to Enhance Energy Harvesting Potential

Division / Sponsors: 
Aerospace Division

Paper Proceedings: https://asmedigitalcollection.asme.org/SMASIS/SMASIS2020/volume/84027

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