Experimental observation of elastic wave demultiplexer in phononic slab waveguides

Abstract

Phononic Crystal (PnC) is a periodic artificial crystal made of two different elastic constant materials capable of manipulating the acoustic/elastic wave. The acoustic properties of this PnC, namely, phononic bandgap (PnBg), which is defined as frequency region with no propagation of acoustics/elastics modes regardless the polarization, have attracted increasing interest amongst the phononic research community. One central research area focuses on the PnC is a demultiplexing phenomena, created from multiple waveguides systems to filter multiple frequency transmissions. The current state-of-theart research on PnC demultiplexer produces limited and narrow pass-band transmission to avoid frequency interactions, resulting in tight and slender filtering ability. In contrast, wide and continuous frequencies are never demonstrated, whether by simulation nor experiments. Also, several reports on PnC demultiplexing use a non-definitive approach, which relies on the fluid property and thermal influence; hence subjected to the influence of the surrounding environment. Therefore, a pristine environment is needed to maintain the filtering ability for such PnC system at all times. This current research objective is to study the vide supra research gap of a wide-range demultiplexing system consisting of three distinct linear waveguides for elastic wave filtering application using theoretical and experimental approaches. The theoretical approach to simulate multiple waveguides systems for the demultiplexing application was demonstrated using the finite element method (COMSOL Multiphysics software). Experimentally, the phononic device was built from additive manufacturing, i.e., direct metal Laser Sintering (3D ProX300). A piezoelectric ceramic transducer provided the elastic stimulation, and the transmission coefficient spectra were measured and confirmed with a microsystem analyzer. Then, the wave propagation behavior of this device was confirmed with the surface cartography measurement from a laser doppler vibrometer. Theoretical simulations and experimental results confirmed the demultiplexing from the transmitting and suppressing of three different frequencies between 270 kHz and 325 kHz from the three waveguide openings. The surface cartography measurement further showed that the incident wave frequencies were routed into one waveguide with a distinct wave attenuation observed in the other two channels. The proposed phononic device had the flexibility and freedom to supports wide and continuous wide spectrum frequency filtering. Finally, this result could be further explored for droplet manipulations in biological applications.