  Elastic and acoustic metamaterials can sculpt dispersion of waves through
resonances. In turn, resonances can give rise to negative effective properties,
usually localized around the resonance frequencies, which support band gaps at
subwavelength frequencies (i.e., below the Bragg-scattering limit). However,
the band gaps width correlates strongly with the resonators' mass and volume,
which limits their functionality in applications. Trampoline phenomena have
been numerically and experimentally shown to broaden the operational frequency
ranges of two-dimensional, pillar-based metamaterials through perforation. In
this work, we demonstrate trampoline phenomena in lightweight and planar
lattices consisting of arrays of Archimedean spirals in unit cells.
Spiral-based metamaterials have been shown to support different band gap
opening mechanisms, namely, Bragg-scattering, local resonances and inertia
amplification. Here, we numerically analyze and experimentally realize
trampoline phenomena in planar metasurfaces for different lattice
tessellations. Finally, we carry out a comparative study between trampoline
pillars and spirals and show that trampoline spirals outperform the pillars in
lightweight, compactness and operational bandwidth.
