Simulation Of Surface Acoustic Wave Research Articles

2Pb2-9 Simulation of Surface Acoustic Wave in Shallow Layer of Heated Mortar Under Multi-frequency Ultrasound Irradiation

2Pb2-9 Simulation of Surface Acoustic Wave in Shallow Layer of Heated Mortar Under Multi-frequency Ultrasound Irradiation

Applicability of single precision graphics processing unit for fast simulation of 2D surface acoustic wave devices using an hierarchical cascading technique

This paper discusses the applicability of a single precision computation with a graphics processing unit for the finite elements method simulation of surface acoustic wave (SAW) devices using the hierarchical cascading technique (HCT). The HCT simulation is performed in both single and double precision, and the required computational time, memory size and accuracy are compared. Three SAW device structures are discussed; (a) a synchronous resonator on 42°YX-LiTaO3 (42-LT), (b) a double mode SAW (DMS) filter on 42-LT, and (c) a synchronous resonator on 42-LT/Si bonded wafer. It is shown that the single precision enables us to double the calculation speed and halve the memory size with negligible accuracy deterioration.

Hierarchical Cascading Algorithm for 2-D FEM Simulation of Finite SAW Devices.

Application of the finite-element method (FEM) for the simulation of surface acoustic wave (SAW) devices has been constrained by the large number of degrees of freedom required, resulting in large memory usage and long computation times. We propose a new 2-D algorithm that takes advantage of the periodic structure typical of SAW devices. The device is partitioned into small, repeatedly occurring building blocks. Only unique building blocks are simulated with FEM. The device geometry is presented as a hierarchical tree of cascading operations, where smaller blocks are combined into larger blocks. This is equivalent to the full FEM simulation of the device, implying the drastic reduction of memory consumption and simulation time for structures with a high degree of periodicity. The method is verified against FEM/BEM-based software. To ensure accurate and efficient simulation, the boundary conditions should be chosen according to the anisotropy of the substrate crystal.

3D measurement and simulation of surface acoustic wave driven fluid motion: a comparison.

The characterisation of the fluid motion induced by the acoustic streaming effect is of paramount interest for novel microfluidic devices based on surface acoustic waves (SAWs), e.g. for a detailed description of the achievable mixing efficiency and thus the design of such devices. Here, we present for the first time a quantitative 3D comparison between experimental measurements and numerical simulations of the acoustic streaming induced fluid flow inside a microchannel originating from a SAW. On the one hand, we performed fully three-dimensional velocity measurements using the astigmatism particle tracking velocimetry. On the other hand, we derived a novel streaming force approach solving the damped wave equation, which allows fast and easy 3D simulations of the acoustic streaming induced fluid flow. Furthermore, measurements of the SAW amplitude profile inside the fluid filled microchannel were performed. Based on these results, we obtained a very good agreement between the velocity measurements and the simulations of the fluid flow demonstrating the importance of comprising the actual shape of the SAW amplitude profile for quantitatively reliable simulations. It is shown that the novel streaming force approach is a valid approximation for the simulation of the acoustic streaming induced fluid flow, allowing a rapid and simple estimation of the flow field of SAW based microfluidic devices.

Numerical Simulation of Surface Acoustic Wave Actuated Separation of Rigid Enantiomers by the Fictitious Domain Lagrange Multiplier Method

Abstract Enantiomers are chiral objects which differ by their orientation and are thus referred to as left-handed and right-handed enantiomers. In applications they mostly occur as so-called racemic compounds consisting of approximately the same amount of left- and right-handed species which may have completely different properties. Hence, the separation of left- from right-handed enantiomers is an important issue. Conventional technologies are based on gas or high pressure liquid chromatography, capillary electrophoresis, or nuclear magnetic resonance, but typically they are slow and require costly chiral media. A new idea for separation of chiral objects is based on introducing them in certain vorticity patterns, which has been shown to work in theory for an extremely simplified setting by Kostur et al. [Phys. Rev. Lett. 96 (2006), 014502-1–014502-4]. In this paper, we investigate whether these ideas can be successfully adapted to a more realistic setup which can be implemented experimentally. For this purpose, we simulate transport of rigid chiral particles in a fluidic environment by an application of the fictitious domain Lagrange multiplier method due to Glowinski et al. [J. Comput. Phys. 169 (2001), 363–427] which has been designed to study the motion of rigid particles in carrier fluids. Numerical results are presented which illustrate the feasibility of enantiomer separation in flow fields consisting of pairwise counter-rotating vortices. Moreover, a first experimental setup based on surface acoustic wave generated vorticity patterns on the surface of a carrier fluid is devised which reflects the idealized numerical model and gives promising results with respect to properties of particle propagation. These findings may lead to a new technology for enantiomer separation which is both fast and cost-effective.

Numerical simulation of surface acoustic wave actuated enantiomer separation by the finite element immersed boundary method

Enantiomers are chiral objects such as chemical molecules that can be distinguished by their handedness. They typically occur as racemic compounds of left- and right-handed species which may have completely different properties. Therefore, in applications such as drug design in pharmacology, enantiomer separation is an important issue. Here, we present a new technology for enantiomer separation by surface acoustic wave generated vorticity patterns consisting of pairwise counter-rotating vortices in a carrier fluid. The enantiomers are injected onto the surface of the fluid between two counter-rotating vortices such that right-handed (left-handed) enantiomers get attracted by left-rotating (right-rotating) vortices. In particular, we are concerned with the numerical simulation of this separation process by an application of the finite element immersed boundary method which relies on the solution of a coupled system consisting of the incompressible Navier–Stokes equations and the equations of motion of the immersed enantiomers described with respect to an Eulerian and a Lagrangian coordinate system. For a model system of deformable, initially L-shaped enantiomers the results of the numerical simulations reveal a perfect separation.

Numerical simulation of surface acoustic wave actuated cell sorting

Abstract We consider the mathematical modeling and numerical simulation of high throughput sorting of two different types of biological cells (type I and type II) by a biomedical micro-electro-mechanical system (BioMEMS) whose operating behavior relies on surface acoustic wave (SAW) manipulated fluid flow in a microchannel. The BioMEMS consists of a separation channel with three inflow channels for injection of the carrier fluid and the cells, two outflow channels for separation, and an interdigital transducer (IDT) close to the lateral wall of the separation channel for generation of the SAWs. The cells can be distinguished by fluorescence. The inflow velocities are tuned so that without SAW actuation a cell of type I leaves the device through a designated outflow channel. However, if a cell of type II is detected, the IDT is switched on and the SAWs modify the fluid flow so that the cell leaves the separation channel through the other outflow boundary. The motion of a cell in the carrier fluid is modeled by the Finite Element Immersed Boundary method (FE-IB). Numerical results are presented that illustrate the feasibility of the surface acoustic wave actuated cell sorting approach.

Numerical simulation of surface acoustic wave and detection of surface crack in steel

The surface acoustic wave (SAW) propagating in a sample of steel is simulated by using finite element method (FEM). The waves are excited by a load function with propagation properties such as phase velocity dispersion and wide bandwidth. A two-dimensional model consisting of surface defects loaded with a wideband 50–200 MHz and short time 0.1 μs displacement function is investigated in the time and frequency domains. By transient dynamic analysis, Fourier transform and dispersion calculation, snapshots of propagating wave and responses from sensing points are presented. It is indicated that this supervision approach is sensitive to the surface cracks and reflections.

Simulation of Birefringence and Absorption in InGaAs-GaAs Multiple Quantum Well Acoustooptic Modulators Operating Near 980 nm

This paper presents the simulation of surface acoustic wave (SAW)-induced absorption coefficient and refractive index change in InGaAs-GaAs multiple quantum well (MQW) structures operating near 980 nm. The exciton problem is solved in two dimensional momentum space to include the non-axial effect due to strain induced valance band mixing and nonparabolicity. The optical absorption coefficient and refractive index changes near the band gap in the MQWs are calculated as a function of SAW power.

Modeling, simulation, and design of SAW grating filters

A systematic procedure for modeling, simulating, and designing SAW (surface acoustic wave) grating filters, taking losses into account, is described. Grating structures and IDTs (interdigital transducers) coupling to SAWs are defined by cascadable transmission-matrix building blocks. Driving point and transfer characteristics (immittances) of complex architectures consisting of gratings, transducers, and coupling networks are obtained by chain-multiplying building-block matrices. This modular approach to resonator filter analysis and design combines the elements of lossy filter synthesis with the transmission-matrix description of SAW components. A multipole filter design procedure based on a lumped-element-model approximation of one-pole two-port resonator building blocks is given and the range of validity of this model examined. The software for simulating the performance of SAW grating devices based on this matrix approach is described, and its performance, when linked to the design procedure to form a CAD/CAA (computer-aided design and analysis) multiple-filter design package, is illustrated with a resonator filter design example.