Interaction of a Contact Resonance of Microspheres with Surface Acoustic Waves

Abstract

We study the interaction of surface acoustic waves (SAWs) with a contact-based vibrational resonance of 1 μm silica microspheres forming a two-dimensional granular crystal adhered to a substrate. The laser-induced transient grating technique is used to excite SAWs and measure their dispersion. The measured dispersion curves exhibit "avoided crossing" behavior due to the hybridization of the SAWs with the microsphere resonance. We compare the measured dispersion curves with those predicted by our analytical model and find excellent agreement. The approach presented can be used to study the contact mechanics and adhesion of micro- and nanoparticles as well as the dynamics of microscale granular crystals.

Vibrational dynamics of a two-dimensional microgranular crystal

“…The mode labeled V corresponding to the most prominent peak in the spectra, as shown in Fig. 2(e), was previously identified as the vertical contact resonance mode [7,9,10]. Figure 2(e) also shows small peaks to either side of the V-mode peak which we assigned to horizontal-rotational modes labeled HR and RH following Ref.…”

“…The initial efforts focused on the vertical contact resonance of microspheres, arising due to contact with the substrate, and its interaction with surface acoustic waves (SAWs). In these initial studies, the observed phenomena, such as an avoided crossing in the Rayleigh SAW dispersion [7] and the resonant attenuation of SAWs by microspheres [9], could be well accounted for by a simple model where microspheres did not interact with each other [7]. Refined measurements of the resonant attenuation of SAWs * avegaflick@gmail.com † maznev@mit.edu revealed horizontal-rotational modes enabled by interparticle interactions [10].…”

“…A new frontier was opened by laser-based experiments on 2D selfassembled monolayers of micron-sized particles on a solid substrate [7][8][9][10][11]. These experiments revealed the crucial role of adhesion, which is negligible for large particles but becomes an important factor in determining the contact stiffness at the microscale.…”

Waveguiding by a locally resonant metasurface

“…The first case is exemplified by surface Rayleigh waves on a solid half-space. The interaction of vertical surface oscillators with a Rayleigh wave has been studied theoretically [17,18] and recently observed experimentally [5]. In this case a classic avoided crossing takes place.…”

“…In acoustics, this phenomenon has attracted renewed attention more recently [2][3][4][5][6] in the context of sound propagation in artificial media referred to as locally resonant metamaterials [2]. It is well known that in a medium containing resonant inclusions [2,[7][8][9][10][11][12], propagating waves hybridize with the local resonance resulting in an avoided crossing bandgap, as shown in Fig.…”