Phononic crystals offer an innovative platform for acoustic liquid sensors Based on a longitudinal cavity mode, we introduce an acoustic sensor system using a two dimensional phononic crystal with in-plane wave incidence The phononic crystal is made up of a steel plate having two regular arrays of holes and a cavity in-between The holes and the cavity are filled with the liquid of interest We both theoretically and experimentally demonstrate that the transmission peak caused by the cavity mode can be used for sensor purpose Theoretical simulation and experimental measurement show good consistency in the response of the transmission peak frequency This frequency is primarily sensitive to the speed of sound thereby sensitive to the composition of the liquid mixture

Two-dimensional phononic crystal sensor based on a cavity mode

In-plane elastic wave propagation and band-gaps in layered functionally graded phononic crystals

A new sensor platform is based on so-called phoxonic crystals Phoxonic crystals are structures designed for simultaneous control of photon and phonon propagation and interaction They are characterized by a periodic spatial modulation of the dielectric constant as well as elastic properties on a common wavelength scale Multiple scattering of photons and phonons results in a band gap where propagation of both waves is prohibited The existence of photonic and phononic band gaps opens up opportunities for novel devices and functional materials The usage of defect modes is an advantageous concept for measurement The defect also acts as point of measurement We show theoretically that the properties of the defect mode can be tailored to provide very high sensitivity to optical and acoustic properties of matter confined within a defect cavity or surrounding the defect or being adsorbed at the cavity surface In this paper, we introduce the sensor platform and analyze the key features of the sensor transduction scheme Experimental investigations using a macroscopic device support the theoretical findings

Phoxonic crystals—a new platform for chemical and biochemical sensors

We perform a theoretical study based on the transmissions of optical and acoustic waves normally impinging to a periodic perforated silicon plate when the embedded medium is a liquid and show the existence of Fano-like resonances in both cases. The signature of the resonances appears as well-defined asymmetric peaks in the phononic and photonic transmission spectra. We show that the origin of the Fano-like resonances is different with respect to the nature of the wave. In photonic, the origin comes from guided modes in the photonic plate while in phononic we show that it comes from the excitation of standing waves confined inside the cavity coming from the deformation of the water/silicon edges of the cylindrical inclusion. We finally use these features for sensing and show ultra-sensitivity to the light and sound velocities for different concentrations of analytes.

/pdf/optical-and-acoustic-sensing-using-fano-like-resonances-in-139su4jlbj.pdf

Optical and acoustic sensing using Fano-like resonances in dual phononic and photonic crystal plate

In this work, a one-dimensional porous silicon carbide phononic crystal (1D-PSiC PnC) sandwiched between two rubber layers is introduced to obtain low frequency band gaps for the audible frequencies. The novelty of the proposed multilayer 1D-PnCs arises from the coupling between the soft rubber, unique mechanical properties of porous SiC materials and the local resonance phenomenon. The proposed structure could be considered as a 1D acoustic Metamaterial with a size smaller than the relevant 1D-PnC structures for the same frequencies. To the best of our knowledge, it is the first time to use PSiC materials in a 1D PnC structure for the problem of low frequency phononic band gaps. Also, the porosities and thicknesses of the PSiC layers were chosen to obtain the fundamental band gaps within the bandwidth of the acoustic transducers and sound suppression devices. The transmission spectrum of acoustic waves is calculated by using the transfer matrix method (TMM). The results revealed that surprising low band gaps appeared in the transmission spectra of the 1D-PSiC PnC at the audible range, which are lower than the expected ones by Bragg’s scattering theory. The frequency at the center of the first band gap was at the value 7957 Hz, which is 118 times smaller than the relevant frequency of other 1D structures with the same thickness. A comparison between the phononic band gaps of binary and ternary 1D-PSiC PnC structures sandwiched between two rubber layers at the micro-scale was performed and discussed. Also, the band gap frequency is controlled by varying the layers porosity, number and the thickness of each layer. The simulated results are promising in many applications such as low frequency band gaps, sound suppression devices, switches and filters.

/pdf/locally-resonant-phononic-crystals-at-low-frequencies-based-1ex1j5t726.pdf

Locally Resonant Phononic Crystals at Low frequencies Based on Porous SiC Multilayer

The contribution presents the sensor application of a resonance-induced extraordinary transmission through a regular phononic crystal consisting of a metal plate with a periodic arrangement of holes in a square lattice at normal incidence of sound. The characteristic transmission peak has been found to strongly depend on sound velocity of the liquid the plate is immersed in. The respective peak maximum frequency can serve as measure for the concentration of a component in the liquid mixture, if a beneficial relation to the speed of sound of the liquid exists. Experimental verification has been performed with mixtures of water and propanol as model system. Here we especially pay attention to numerical calculations based on EFIT and COMSOL which reveal more insides to the wave propagation characteristics. Experimental investigations with Schlieren method and laser interferometry support the theoretical findings.

2D phononic crystal sensor with normal incidence of sound

We report on first steps towards a phononic crystal sensor for biomedical applications. Phononic crystal sensors are a new concept following the route of photonic crystal sensors. Basically, the material of interest constitutes one component of the phononic crystal. Here a liquid analyte is confined in a disposable element which acts as defect in a phononic crystal. In an application as biomedical sensor the concentration of a compound in liquid must be related to speed of sound of the liquid in the cavity. A change in the concentration e.g. caused by the appearance of a toxic compound or as a result of a biochemical reaction, results in measurable changes in the transmission coefficient, specifically a shift of a resonance induced transmission peak. Three additional key design challenges for a medical sensor are the strong restriction coming from limitations to approved materials for the analyte container, geometric dimensions in the mm-or sub-mm-range common in hospital or point-of-care environment and acoustic coupling between sensor platform and the analyte container.

http://ieeexplore.ieee.org/iel7/6971895/6984913/06985147.pdf

Phononic cystal sensor for medical applications

Acoustic band gap materials, so-called phononic crystals, provide a new sensor platform. Phononic crystals are periodic
composite materials with spatial modulation of elasticity, mass density as well as longitudinal and transverse velocities
of elastic waves. When utilized as sensor, the input parameter to be measured changes characteristic properties of the
phononic crystal in a distinct manner. These changes can be detected by measuring the transmission behavior of
ultrasonic waves through the phononic crystal. The most optimal feature for detection is a sharp isolated transmission
peak which corresponds to the input parameter. When applying as liquid property sensor one component building the
phononic crystal is the liquid to be analyzed. Here we present recent results gathered from different sensor realizations.
In the second part we report on experimental investigations based on laser vibrometry which provide deeper insides to
the so-called extraordinary transmission. These analyses reveal that structural resonance effects are responsible for the
smart properties of the device.

Ralf Grundmann

Papers

2D phononic crystal sensor with normal incidence of sound

Phononic cystal sensor for medical applications

Phononic crystal sensor for liquid property determination