Manfred Weihnacht

Crystal Acoustics Research Services - innoXacs Dr. Manfred Weihnacht

Using surface acoustic waves (SAW) for the agitation and manipulation of fluids and immersed particles or cells in lab-on-a-chip systems has been state of the art for several years. Basic tasks comprise fluid mixing, atomization of liquids as well as sorting and separation (or trapping) of particles and cells, e.g. in so-called acoustic tweezers. E...

The present paper studies experimentally and numerically the surface acoustic wave (SAW) field on a piezoelectric substrate generated by interdigital transducers (IDT). On the one hand, mechanical displacements produced by the SAW are measured with the help of a laser Doppler vibrometer. On the other hand, mechanical displacements are computed by t...

The paper numerically studies the contribution of the electric field accompanying the surface acoustic wave to the actuation of the acoustic streaming in microchannels. The finite element method is used. The results obtained as applied to the surface waves on 128° and 64°-rotated Y cuts of LiNbO3 demonstrate that the force created by the electric f...

The paper numerically investigates the transmission of harmonic surface acoustic waves (SAWs) across the perfectly bonded and perfectly sliding contacts between two 90°-wedges, at least one of which possessing piezoelectric properties. The finite element method in frequency domain is used. The structures are constructed of lithium niobate, fused qu...

The paper analyzes the possibility of using predominantly boundary polarized surface acoustic waves for actuating fluidic effects in microchannels fabricated inside containers made of PDMS. The aim is to remove a shortcoming peculiar to conventionally utilized predominantly vertically polarized waves. Such waves strongly attenuate while they propag...

Transmission of a harmonic SAW across the interface between two elastically anisotropic 90°-wedges is studied using FEM in frequency domain. The wedges are in contact along a pair of their faces. The contact is either perfectly rigid or perfectly sliding. The structures under modelling are constructed of LiNbO 3 , Si and GaAs. It is assumed that th...

The numerical study is performed of the harmonic Rayleigh wave scattering in a composite structure constructed from two elastically isotropic 90°-wedges. These wedges are in contact along one pair of their faces. It is assumed that either the perfectly sliding contact or the perfectly rigid one is realized. The other pair of faces forms a plane bor...

In the late 80ths we constructed a light fibre interferometer, which could measure the voltage-induced thickness variations of piezoelectric samples down to some few picometres. The principle of the interferometer is explained and four methods to minimize noise. With this sensor, we started a home-made PFM in February 1993. The very first pictures...

The high-frequency pressure induced by a surface acoustic wave in the fluid filling a microchannel is computed by solving the full scattering problem. The microchannel is fabricated inside a container attached to the top of a piezoelectric substrate where the surface wave propagates. The finite element method is used. The pressure found in this way...

The permittivity spectra of solid solutions (1–x)SrTiO3–xDyScO3 (x = 0, 0.01, 0.03) and ceramic samples of strontium titanate doped with Sc3+ ions have been studied in the frequency range from 10 Hz to 1MHz. It has been found that the permittivity exhibits maxima at cryogenic temperatures, and the dielectric relaxation processes are observed in the...

Dielectric measurements of disordered La3Ga5SiO14 (LGS), La3Ga5,5Ta0,5O14 (LGT) and ordered Sr3NbGa3Si2O14 (SNGS), Sr3TaGa3Si2O14 (STGS) single crystals of the langasite family performed at frequencies from 10 Hz to 1 MHz at temperatures between 4.2 and 300 K are reported. Temperature dependences of dielectric permittivity ε33 and ε11 are obtained....

The elastic properties of new piezoelectric Sr3NbGa3Si2O14 crystals of the langasite (lanthanum gallium silicate) family have been investigated. The temperature dependences of the elastic constants C 11, C 33, C 66, and C 44 have been measured in a wide temperature range from 300 to 4.2 K. The characteristic parameters of the crystal associated wit...

We present an acoustic study of 0.55 PbMg1/3Nb2/3O3 - 0.45 PbSc1/2Nb1/2O3 relaxor ferroelectric solid solution in a wide temperature range, from 150 to 750 K. The longitudinal acoustic wave velocity and attenuation were measured by the ultrasonic pulse-echo technique at frequency 10 MHz. The strong anomalies observed in the longitudinal sound veloc...

The harmonic surface acoustic wave (SAW) scattering at 90-degree corners of piezoelectric substrates is studied by FEM. The SAW is incident perpendicular to the vertical border. The dependences of the reflection and transmission coefficients on the radius of the fillet at the corner are found for 128°YX and YZ LiNbO3 as well as ST-X quartz substrat...

The paper numerically studies the harmonic Rayleigh wave scattering at the 90-degree corner of isotropic substrate. The finite element method is used. The main attention is paid to two cases. The first one is the apex of the substrate corner is rounded off. The second one consists in that a layer of foreign material is deposited on the face which s...

The dielectric and acoustic properties of (1 − x)SrTiO3−xBiFeO3 solid solutions (0 ≤ x ≤ 1) have been studied in the temperature range from 4.2 to 850 K. Evolution of the antiferrodistortive transition and its suppression in the concentration range 0.1 < x < 0.2 have been revealed. X-ray diffraction data obtained at room temperature, as well as the...

We present an acoustic study of relaxor ferroelectrics with magnetic ordering PbFexB1−xO3 (B = Nb, Ta, W) in the wide temperature range from 100 to 750 K as well as relaxor PbMg1/3Nb2/3O3 at temperatures from 300 to 750 K. The longitudinal and transverse acoustic wave velocity and attenuation have been measured by the ultrasonic pulse-echo techniqu...

A numerical study is performed of the oblique reflection of a surface acoustic wave from a strip of finite width deposited on the surface of a half-infinite substrate. The finite element method is used. If the strip–substrate contact supports waveguide modes with the velocity exceeding the surface wave velocity on the free surface of the substrate,...

A novel type of interdigital transducers (IDT) on surface acoustic waves with two quarter-wavelength electrodes per one-wavelength IDT period was proposed recently for the multi-track solution consisting of alternating active IDT tracks and passive reflector tracks. Such 2D-periodic structure permits to implement single-phase unidirectional transdu...

The SAW reflection from a strip (Pt, Al) deposited on a half-infinite substrate (Z-cut AlN) is numerically studied. The strip-substrate contact forms an acoustic waveguide supporting leaky modes propagating faster than SAW on the free surface of the substrate. The excitation of a leaky mode by SAW leads to a singular behavior of the reflection and...

We have successfully grown high quality large size piezoelectric single crystals of Ca3TaGa3Si2O14 (CTGS) by the Czochralski technique. The elastic material constants were derived from bulk- and surface acoustic wave measurements. Starting with the elastic constants determined from BAWs we optimized the data set by measuring SAW velocities as a fun...

Elastic properties of multiferroic PbFe2/3W1/3O3 (PFW) ceramics have been studied in a temperature range of 4.2–400 K, which contains the regions of existence of the ferroelectric relaxor and antiferromagnetic phases. The longitudinal, shear, and bulk elasticity moduli, Young’s modulus, and Poisson’s ratio of PFW ceramics have been determined for t...

A numerical study is carried out of the surface acoustic wave generation by a bulk acoustic wave in a half-infinite anisotropic half-space without piezoeffect. The efficient conversion of bulk waves into surface waves occurs due to a grating area created on the surface of the substrate. Our simulations are fully based on the finite element method....

The paper studies the difference between the reflection coefficients of a surface acoustic wave incident on a groove or strip along the inverse directions. This difference occurs because of the crystallographic anisotropy of the substrate and/or the asymmetry of the shape of the obstacle. The numerical computations are carried out by the finite ele...

FEM simulations of the SAW-BAW conversion in gratings of finite length are carried out for Si substrate. The grating is created from rectangular grooves or strips (Al, Cu). When simulating the SAW generation, we determine the SAW amplitude and investigate its dependence on the frequency and the polarization of the incident BAW, the length of the gr...

Using the pulse-echo ultrasonic method, the velocities of the longitudinal and the shear bulk acoustic waves propagating in four crystallographic directions of YCa4O(BO3)3 and NdCa4O(BO3)3 monoclinic single crystals were measured at room temperature and nine elastic constants were obtained. Some elastic constants important for possible acoustic app...

The longitudinal and transverse acoustic wave velocities in PbFexB1-xO3 (B = Ta, Nb, W) ceramics have been measured by the ultrasonic pulse-echo technique at a frequency of 10 MHz in a wide temperature range from 4.2 K to 500 K. Temperature dependences of the longitudinal and transverse elastic constants were obtained. The softening of the elastic...

Using the pulse-echo ultrasonic technique, the velocities of the longitudinal and the shear bulk acoustic waves propagating in five crystallographic directions of langasite single crystal were measured in a wide temperature range from 25°C to 600°C. Piezoelectric coefficients and dielectric permittivity as a function of temperature are also obtaine...

Non-reflective interdigital transducers (IDTs) for surface acoustic waves (SAWs) are important elements for development of SAW devices with precise frequency responses. Until now a common way to have a non-reflective periodic cell of IDT at the resonance frequency is to use split electrodes with periodicity P/4 and finger width P/8, where P is the...

The longitudinal acoustic wave velocity and attenuation in PbFe 1/2 Nb 1/2 O 3 and PbMg 1/3 Nb 2/3 O 3 ceramics have been measured by pulse-echo technique at a frequency of 10 MHz in the temperature range from 200 to 700 K. The anomalies observed in the sound velocity and attenuation behavior versus temperature are correlated with temperature range...

The paper discusses the numerical study of the SAW reflection from single surface imperfections, such as grooves, projections, and steps, on half-infinite piezoelectric substrates. Our analysis is based on FEM computations. A perfectly matched layer (PML) is implemented in order to truncate the computational domain. The amplitude of the reflected S...

A general analysis on the subject of acoustic axes for bulk acoustic waves in trigonal crystals is presented. It is shown that the effect of piezoelectricity increases the maximum allowable number of acoustic axes in the plane of elastic symmetry from three to five for trigonal crystals of class 3m, and from 3 to 7 for trigonal crystals of class 32...

Lagrange interpolation formula is proposed for the reconstruction of the spatial distribution of polarization from a pyroelectric current spectrum. Numerical examples with simulated data and experimental results are given.

In this paper a new tool simultaneously to detect viscoelastic and dielectric properties of human fluids is presented. Therefore, one-port SAW resonators (SAW … surface acoustic wave) with fundamental modes of 85, 170 und 340 MHz were developed. Shear horizontal polarized surface acoustic waves (SH-SAW) are used to detect the viscoelastic propertie...

The paper is devoted to the numerical investigation of the difference between the reflection coefficients of the SAW incident on a groove/strip along the inverse directions. This difference occurs because of the crystallographic anisotropy of the substrate or/and the asymmetry of the shape of the groove/strip. The computations are carried out by th...

The longitudinal acoustic wave velocity and attenuation in BiFeO3 ceramics have been measured by ultrasonic pulse-echo technique at a frequency of 10 MHz in the temperature range from 4.2 K to 830 K. The anomalies observed in the sound velocity and attenuation behavior versus temperature are attributed to the assumed relaxation in the temperature r...

The longitudinal acoustic wave velocity and attenuation in PbFe1/2Ta1/2O3 and BiFeO3 ceramics have been measured by ultrasonic pulse-echo technique in the temperature range from 50 K to 530 K and from 250 K to 830K, respectively. The anomalies observed in the sound velocity behavior versus temperature in the case of PbFe1/2Ta1/2O3 were correlated w...

Ceramic samples of (1 − x)SrTiO3-xLiNbO3 (0 ≤ x ≤ 0.05) solid solutions are synthesized. The dielectric and acoustic properties of the solid solutions are studied in the temperature range from 15 to 300 K. It is revealed that the polar state characterized by the dispersion of the permittivity and the dielectric hysteresis occurs at low temperatures...

Epitaxial wurtzite aluminum nitride (AIN) films have been grown on (111) oriented silicon substrates by plasma-assisted solid source molecular beam epitaxy (MBE). The growth has been performed in the two-dimensional (2D) growth mode. Occuring surface reconstructions have been monitored by reflection of high-energy electron diffraction (RHEED). The...

During the last decades thickness shear mode resonators (TSM, QCM) have been object of comprehensive research. Many approaches were made to describe the behavior and physical effects when loaded. We present a physical model that describes the TSM in the full frequency range, including overtones for a large variety of loadings (e.g. gases, liquids o...

This paper discusses the application of the finite element method to the simulation of surface acoustic wave generation on piezoelectric substrates and the possibility of reducing the number of computations by taking into account the symmetry of the problem. It is shown that the computations can be performed in only one half of the structure provid...

The effect of Li on the phase state of SrTiO3 was studied to clarify the predominant factors of induced polar state in incipient ferroelectrics. Dielectric, ultrasonic and polarization loops measurements were carried out in a temperature range of 3–350 K using ceramic samples of LixSr1-xTiO3-x/2 (0 ≤ x ≤ 0.05). The observed relaxor-like features ar...

The paper studies, by the finite element method, the reflection of surface acoustic waves from single obstacles of regular shapes on the surface of piezoelectric materials. The so-called perfectly matched layer is used to truncate the computational domain. The following types of imperfections are considered: single steps, grooves, and projections,...

An analytical approach is presented to describe acoustic thickness shear mode resonators in the full frequency range, including all overtones. The absolute value of loadings with complex properties (e. g. complex viscosity or shear modulus) can be determined by curve fitting. Loadings with complex behaviour like polymer layers have been studied and...

The recently proposed new regular electrode structure called ring waveguide resonator (RWR) on surface acoustic waves (SAW) is optimized to have a single radial mode excitation. The structure consists of a gold (Au) interdigital transducer (IDT) in the form of a ring placed on the Z-cut of aluminum nitride (AlN). The IDT itself creates a waveguide...

This paper discusses the application of FEM to the simulation of the SAW generation by IDTs and the possibility of reducing the amount of computations by taking into account the symmetry. The perfectly matched layer (PML) is used to truncate the computational domain. A test computation of the electric admittance agrees well with experimental result...

The longitudinal acoustic wave velocity and attenuation in PbFe1/2Ta1/2O3 ceramics have been measured by pulse-echo technique in the temperature range from 4.2 to 530 K. The anomalies observed in the sound velocity and attenuation behavior versus temperature were correlated with Burns temperature, temperature range of the coexistence of relaxor fer...

In this paper a new tool to assess viscoelastic and dielectric properties of human fluids is presented. Shear horizontal polarized surface acoustic waves (SH-SAW) are used to detect the viscoelastic properties of coagulating blood and blood plasma samples. One-port SAW resonators, with fundamental modes of 85, 170 und 340 MHz were developed. Additi...

We have successfully grown high-quality AlN piezoelectric single crystal using the sublimation technique. Transparent crack-free boules of approximately 15 mm in diameter and 25 mm in length along the [0001] direction were obtained, with coloring from amber to dark brown depending on growth temperature. Full sets of material parameters of grown AlN...

First results of numerical and physical experiments for the ring waveguide resonator on surface acoustic waves are presented. The structure consists of a gold interdigital transducer in the form of a ring placed on the Z cut of aluminum nitride crystal. Excitation of radial modes is investigated. The electrical admittance frequency dependence of su...

The dielectric and acoustic properties of (1 − x)SrTiO3-xBiFeO3 (0 ≤ x ≤ 0.04) solid solutions have been studied in the temperature range 10–300 K. The polar state exhibiting permittivity dispersion and dielectric hysteresis loops has been revealed at temperatures of 40–100 K. At 20–40 K, we have observed one more dielectric relaxation, which is no...

A new regular electrode structure called ring waveguide resonator (RWR) on surface acoustic waves (SAW) is estimated at first by 3D finite element method (FEM). The structure consists of an aluminum (Al) interdigital transducer (IDT) in the form of a ring placed on the Z-cut of aluminum nitride (AlN). The IDT itself creates a waveguide effect on th...

In the present work, using the well-known numerical procedure for SAW calculation in arbitrary crystals the gyroscopic effect is investigated. To take into account the medium rotation the Coriolis and centrifugal forces are introduced into the piezoelectric medium equations of motion. As a result of the standard procedure, the SAW velocity is calcu...

The specific features of the Rayleigh wave reflection from single surface imperfections of an isotropic substrate are studied by the finite element method. Six types of the imperfections are considered, namely, upstep and downstep, projection and groove, and strip of foreign material coating the substrate and buried into it. The dependence is found...

In this paper a new tool to assess viscoelastic and dielectric properties of biological samples is presented. Shear horizontal polarized surface acoustic waves (SH-SAW) are used to detect the viscoelastic properties of biological samples. Therefore a one-port SAW resonator, with a fundamental mode of 85 MHz was developed. Its electrode structure ca...

The reflection of SAW from single steps as well as single and multiple grooves, projections, and strips on half-infinite isotropic (fused quartz) and piezoelectric (LiNbO3) substrates is investigated by FEM. A perfectly matched layer (PML) is used in order to truncate the computational domain. The amplitude of the reflected SAW is found by applying...

In this paper a new tool to assess viscoelastic and dielectric properties of biological samples is presented. Shear horizontal polarized surface acoustic waves (SH-SAW) are used to detect the viscoelastic properties of the extracellular matrix (ECM) expelled by adhering fibroblast cell cultures. Therefore a one-port SAW resonator, with a fundamenta...

We have successfully grown high quality AlN piezoelectric single crystal by sublimation technique. Transparent and coloring from amber to dark brown (depending on growth temperature) crack-free boules of approximately 15 mm in diameter and 25 mm in length along [0001] direction were obtained. Full sets of material parameters of grown AlN and commer...

In this study, a new way of investigating a surface acoustic wave (SAW) based sensor device is reported. For that, SAW sensors with a fundamental mode of about 85 MHz and a metallization of gold were developed. Realized as one port resonators, these sensors allow the continuous detection of electric and viscoelastic properties of the same living ce...

The elastic, piezoelectric, and dielectric constants of new piezoelectric single crystals Sr3NbGa3Si2O14 (SNGS) are measured. The elastic moduli C 11 and C 66 and the piezoelectric coefficient e 11 are determined over a wide temperature range. It is demonstrated that the piezoelectric activity of the crystal is retained up to the highest temperatur...

Using a one-dimensional approach the electric admittance vertical bar Y vertical bar of a quartz crystal microbalance (QCM) is calculated as a function of frequency depending on material properties as well as the acoustic impedance of an arbitrary loading. Several solutions for the shift of specific frequencies are derived and methods presented to...

Dielectric and acoustic properties of the (1 − x)SrTiO3−xPbMg1/3Nb2/3O3 solid solutions (0 ⩽ x ⩽ 1) have been studied at temperatures ranging from 4.2 to 350 K. It has been found that the improper ferroelastic transition exists up to a concentration x = 0.4 and that the phase transition temperature grows with x increasing from 0 to 0.4. As the conc...

This paper studies acoustic waves in a water layer enclosed between the YZ-LiNbO3 substrate coated with a thin SiO2 layer and the half-infinite domain occupied by silicone rubber. The plane wave spectrum is computed. Numerical estimations are made of the COM-parameters describing a periodic grating deposited on the LiNbO3 substrate under the SiO2 l...

We have successfully grown high quality piezoelectric single crystals of Sr3NbGa3Si2O14 (SNGS) and Sr3TaGa3Si2O14 (STGS) by the Czochralski technique. The piezoelectric stress constant epsiv11 and dielectric permittivity epsiv11 as well as elastic constants C11 E and C66 E were determined at temperatures up to 930degC for both crystals.

In this paper preliminary results for the detection of the cell adhesion process with shear-horizontal polarized surface acoustic wave devices (SH-SAW) are presented. The murine fibroblast cell line L929 was investigated. Therefore a special measurement setup was developed. It enables us to perform long term measurements at stable ambient condition...

We performed a study of the temperature dependence of the dielectric response of (Ba,Sr)TiO3 (BST) ceramics for the whole composition range in a wide frequency range by means of Fourier transform infrared, time-domain THz, microwave and low-frequency dielectric spectroscopy. Room-temperature spectra of the paraelectric dielectric response were comp...

This paper theoretically studies the propagation and the generation of leaky acoustic waves in a fluid layer enclosed between the half-infinite YZ- Li Nb O ₃ (lithium niobate) substrate coated with a thin Si O ₂ (silicone dioxide) layer and the half-infinite domain occupied by silicone rubber. The plane wave spectrum in the st...

The study is devoted to the compositional evolution and interrelation of phases in SrTiO3 - PMN solid solution. Experimental evidences of an antiferrodistortive phase, a relaxor state and their coexistence are obtained.

The applications of QCMs were extended to liquids last years in the context of growing interest in monitoring biological systems that exhibit viscoelastic behavior. A special formula derived in 1985 by Kanazawa and Gordon [1] for the change in oscillation frequency of the crystal due to liquid loading is still widely in use because of its establish...

We have successfully grown high quality piezoelectric single crystal of Sr₃NbGa₃Si₂O₁₄(SNGS) by the Czochralski technique. Transparent and pale yellow boules of approximately 60 mm in length and 16-18 mm in diameter were obtained. A full set of material parameters including dielectric, elastic and piezoel...

We report on lattice dynamics and far infrared dielectric response of Sr1-xBaxTiO3 ceramics with small concentration of Ba (0.01 <= x <= 0.2). Reflectivity spectra were obtained on cooling down to 5 K by Fourier transform interferometer in the 25-650 cm(-1) frequency range and by coherent-source submillimetre technique in the 30-40 cm(-1) range and...

A simple regular electrode structure for surface acoustic wave (SAW) devices is proposed. The structure consists of an interdigital transducer in the form of a ring placed on the Z cut of a hexagonal piezoelectric crystal. Finite thickness electrodes produce the known slowing effect for a SAW in comparison with this SAW on a free surface. The close...

The article is focused on the compositional evolution and interrelation of phases in (1-x) SrTiO ₃-x PbZrO ₃ solid solution. The results of dielectric and ultrasonic wave velocity measurements in a temperature range from 4.2 to 600 K are reported. Experimental evidences of a ferroelectric phase transition at the critical conce...

In our previous work we demonstrated the general suitability of surface and bulk acoustic wave (SAW and BAW) structures for recording the continuous change of fluidic behavior in the course of blood coagulation processes [Guhr et al.,2005]. Special advantage can be taken from the direct impact of fluid consistence on SAW and BAW device parameters (...

A new closed regular electrode structure for future surface acoustic wave (SAW) devices is described. The structure consists of an interdigital transducer in the form of a ring placed on the Z cut of a hexagonal piezoelectric crystal. Finite thickness electrodes produce the known slowing effect for a SAW in comparison with this SAW on a free surfac...