SURFACE ACOUSTIC WAVE INDUCED OPTICAL EFFECTS IN A NEMATIC LIQUID CRYSTAL

1993 ◽  
Vol 07 (17) ◽  
pp. 1167-1171
Author(s):  
A. K. GEORGE
Keyword(s):  
Liquid Crystal ◽  
Theoretical Model ◽  
Acoustic Wave ◽  
Nematic Liquid Crystal ◽  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Acoustic Streaming ◽  
Crystal Film ◽  
Optical Effects ◽  
Wave Induced

The optical changes occurring in a homeotropically aligned nematic liquid crystal film when excited by surface acoustic waves have been studied. Striped domains at low acoustic intensities followed by acoustic streaming at high intensities have been observed. The increase in transparency of the oriented liquid crystal film under the action of surface acoustic waves also has been investigated. The experimental results compare favourably with the available theoretical model based on the effect of rotation of the plane of polarization.

Integrated ZnO Film Based Acoustic Wave Microfluidics and Biosensors

2010 ◽  
Vol 67 ◽  
pp. 49-58 ◽  
Author(s):  
Jack K. Luo ◽  
Y.Q. Fu ◽  
Greg Ashley ◽  
Williams I. Milne
Keyword(s):  
Acoustic Wave ◽  
Acoustic Waves ◽  
Low Cost ◽  
Surface Acoustic Waves ◽  
Acoustic Streaming ◽  
Film Surface ◽  
High Sensitivity ◽  
Zno Film ◽  
Actuation Mechanism ◽  
Saw Devices

Lab-on-a-chip (LOC) is one of the most important microsystems with promising applications in microanalysis, drug development and diagnosis, etc. We have been developing a LOC biodetection system using acoustic wave as a single actuation mechanism for both microfluidics and biosensing using low cost piezoelectric ZnO film. Surface acoustic waves (SAW) coupled into the liquid will induce acoustic streaming, or move the droplet on the surface. These have been utilized to make SAW-based micropumps and micromixers which are simple in structure, easy to fabricate, low cost, reliable and efficient. SAW devices and thin film bulk acoustic resonators (FBAR) have been fabricated on nanocrystalline ZnO thin films deposited using sputtering on Si substrates. A streaming velocity up to ~5cm/s within a microdroplet and a droplet moving speed of ~1cm/s have been achieved. SAW based droplet ejection and vaporization have also been realized. SAW devices and FBARs have been used to detect antibody/antigen and rabbit/goat immunoglobulin type G molecules, showing their high sensitivity. The results have demonstrated the feasibility of using a single actuation mechanism for the LOC.

scholarly journals Influence of X7GeS5I (X = Ag, Cu) Superionic Nanoparticles on Structural Changes in Nematic Liquid Crystal

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 413
Author(s):  
Peter Bury ◽  
Marek Veveričík ◽  
Peter Kopčanský ◽  
Milan Timko ◽  
Ihor P. Studenyak ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Electric Field ◽  
Nematic Liquid Crystal ◽  
Acoustic Waves ◽  
Structural Changes ◽  
Light Transmission ◽  
Surface Acoustic Waves ◽  
Switching Behavior ◽  
Suspension Stability ◽  
Linearly Polarized

The effect of two types of superionic nanoparticles; Cu7GeS5I and Ag7GeS5I, respectively on nematic liquid crystal (6CB) behavior under an external electric field is investigated. The response of both attenuation of surface acoustic waves propagating along with the substrate/liquid crystal interface and light transmission are used to study the structural changes induced by applied electric field. The increasing/decreasing regime as well as jumped change of applied field were used. The light transmission was investigated using linearly polarized laser beam (532 nm) propagating through the liquid crystal. Results obtained from both measurements for three different concentrations (0.01, 0.05 and 0.10 wt%) and in addition two different sizes of nanoparticles are compared and results, relying on structural changes, suspension stability and switching behavior are evaluated.

The size dependant behaviour of particles driven by a travelling surface acoustic wave (TSAW)

Lab on a Chip ◽  
2018 ◽  
Vol 18 (24) ◽  
pp. 3926-3938 ◽  
Author(s):  
Armaghan Fakhfouri ◽  
Citsabehsan Devendran ◽  
Asif Ahmed ◽  
Julio Soria ◽  
Adrian Neild
Keyword(s):  
Particle Size ◽  
Acoustic Wave ◽  
Surface Acoustic Wave ◽  
Sound Source ◽  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Acoustic Streaming

Travelling surface acoustic waves (TSAW) can cause particles to follow the swirling patterns of acoustic streaming, collect in lines or migrate away from the sound source, this paper examines how particle size determines which one of these behaviours occur.

scholarly journals Formation of a Complex Topologies of SAW-Based Inertial Sensors by Laser Thin Film Local Evaporation

Micromachines ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 10
Author(s):  
Alexander Kukaev ◽  
Dmitry Lukyanov ◽  
Denis Mikhailenko ◽  
Daniil Safronov ◽  
Sergey Shevchenko ◽  
...  
Keyword(s):  
Thin Film ◽  
Acoustic Wave ◽  
Surface Acoustic Wave ◽  
Acoustic Waves ◽  
Inertial Sensors ◽  
Surface Acoustic Waves ◽  
Sensing Element ◽  
Small Series ◽  
Evaporation Technique ◽  
Photolithography Process

Originally, sensors based on surface acoustic waves are fabricated using photolithography, which becomes extremely expensive when a small series or even single elements are needed for the research. A laser thin film local evaporation technique is proposed to substitute the photolithography process in the production of surface acoustic wave based inertial sensors prototypes. To estimate its potential a prototype of a surface acoustic wave gyroscope sensing element was fabricated and tested. Its was shown that the frequency mismatch is no more than 1%, but dispersion of the wave on small inertial masses leads to a spurious parasitic signal on receiving electrodes. Possible ways of its neglecting is discussed.

Defects in Nematic Liquid Crystal Film with Geometric Grooves

2015 ◽  
Vol 13 (1) ◽  
pp. 39-46 ◽  
Author(s):  
Xiao-Ji Li ◽  
Zhi-Dong Zhang
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Crystal Film

Electro-optical response of a monolayer polymer dispersed nematic liquid crystal film doped with surfactant

2022 ◽  
pp. 163-211
Author(s):  
V.A. Loiko ◽  
A.V. Konkolovich ◽  
A.A. Miskevich ◽  
M.N. Krakhalev ◽  
O.O. Prishchepa ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Optical Response ◽  
Crystal Film ◽  
Polymer Dispersed

scholarly journals Streaming by leaky surface acoustic waves

2010 ◽  
Vol 467 (2130) ◽  
pp. 1779-1800 ◽  
Author(s):  
J. Vanneste ◽  
O. Bühler
Keyword(s):  
Surface Waves ◽  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Acoustic Streaming ◽  
Stokes Drift ◽  
Mean Flow ◽  
Matched Asymptotics ◽  
Flow Generation ◽  
Solid Liquid Interface ◽  
Solid Liquid

Acoustic streaming, the generation of mean flow by dissipating acoustic waves, provides a promising method for flow pumping in microfluidic devices. In recent years, several groups have been experimenting with acoustic streaming induced by leaky surface waves: (Rayleigh) surface waves excited in a piezoelectric solid interact with a small volume of fluid where they generate acoustic waves and, as result of the viscous dissipation of these waves, a mean flow. We discuss the computation of the corresponding Lagrangian mean flow, which controls the trajectories of fluid particles and hence the mixing properties of the flows generated by this method. The problem is formulated using the averaged vorticity equation which extracts the dominant balance between wave dissipation and mean-flow dissipation. Particular attention is paid to the thin boundary layer that forms at the solid/liquid interface, where the flow is best computed using matched asymptotics. This leads to an explicit expression for a slip velocity, which includes the effect of the oscillations of the boundary. The Lagrangian mean flow is naturally separated into three contributions: an interior-driven Eulerian mean flow, a boundary-driven Eulerian mean flow and the Stokes drift. A scale analysis indicates that the latter two contributions can be neglected in devices much larger than the acoustic wavelength but need to be taken into account in smaller devices. A simple two-dimensional model of mean flow generation by surface acoustic waves is discussed as an illustration.

scholarly journals Influence of Waterproof Films on the Atomization Behavior of Surface Acoustic Waves

Micromachines ◽  
2019 ◽  
Vol 10 (11) ◽  
pp. 794 ◽  
Author(s):  
Huang ◽  
Hu ◽  
Han ◽  
Lei ◽  
Yang
Keyword(s):  
Acoustic Wave ◽  
Surface Acoustic Wave ◽  
Acoustic Waves ◽  
Short Circuit ◽  
Surface Acoustic Waves ◽  
Film Coating ◽  
Experimental Results ◽  
Commercial Application

One of the reasons why commercial application of surface acoustic wave (SAW) atomization is not possible is due to the condensation of aerosol droplets generated during atomization, which drip on the interdigitated transducer (IDT), thereby causing electrodes to short-circuit. In order to solve this problem, a SU-8-2002 film coating on an IDT is proposed in this paper. The waterproof performance of the film coating was tested on a surface acoustic wave (SAW) device several times. The experimental results reveal that the film coating was robust. The experiment also investigated the effects of the SU-8-2002 film on atomization behavior and heating.

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