Flow profile above a quartz crystal vibrating in liquid

Martin, B.A.; Hager, Harold E.

doi:10.1063/1.342771

Cited by 77 publications

(59 citation statements)

References 7 publications

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“…A more detailed theoretical treatment of the propagating acoustic wave that solves the general wave equation of motion for the proper boundary conditions reveals that the shear amplitude along the crystal surface is not uniform but radial symmetric, which in turn means that the quartz resonator is not uniformly sensitive to the adsorption of a foreign material [5,9]. The amplitude is maximum in the center of the evaporated electrode (r = 0) and decreases monotonically with increasing distance from the center, vanishing at the electrode edges (r = R).…”

Section: Mass Sensitivitymentioning

confidence: 99%

Quartz Crystal Microbalance for Bioanalytical Applications

Janshoff

Steinem

2001

Sensors Update

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The quartz crystal microbalance (QCM) was first introduced as a mass sensor in gas phase and in vacuum. Since oscillator circuits capable of exciting shear vibrations of quartz resonators under liquid load have been developed, the QCM became accepted as a new powerful technique to monitor adsorption processes at solid/liquid interfaces in chemical and biological research rendering the method an attractive low‐cost alternative for bioanalytic applications. In the last decade, adsorption of biomolecules on functionalized surfaces turned out to be one of the paramount applications of piezoelectric transducers comprising the interaction of DNA and RNA with complementary strands, specific recognition of protein‐ligands by immobilized receptors, the detection of virus capsids, bacteria, mammalian cells and last but not least the development of complete immunosensors. Piezoelectric transducers allow a label‐free detection of molecules; they are more than mere mass sensors since the sensor response is also influenced by interfacial phenomena, viscoelastic properties of the adhered biomaterial, surface charges of adsorbed molecules and surface roughness. These new insights have recently been used to investigate the adhesion of cells, liposomes and proteins onto surfaces allowing to determine morphological changes of cells as a response to pharmacological substances and changes in the water content of biopolymers in situ. However, future will show whether the quartz crystal microbalance will assert itself against established label‐free sensor devices like surface plasmon resonance spectroscopy and interferometry.

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Section: Mass Sensitivitymentioning

confidence: 99%

Quartz Crystal Microbalance for Bioanalytical Applications

Janshoff

Steinem

2001

Sensors Update

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“…As a consequence of the finite size of the electrodes, the translational disturbance amplitude, and hence sensitivity, is greatest at the center and decreases towards the perimeter in an approximately Gaussian fashion 3,4 .…”

Section: Introductionmentioning

confidence: 99%

“…Solving the Navier-Stokes equation and the equation of continuity with the assumption of a non-uniform shear flow, as required by the finite electrode size, results in flow normal to the surface 3,5 ; the out of plane displacement is around two orders of magnitude smaller than the in-plane displacement. The longitudinal acoustic pressure wave has a wavelength that is dependent upon the acoustic properties of the medium and device frequency.…”

Section: Introductionmentioning

confidence: 99%

Compressional acoustic wave generation in microdroplets of water in contact with quartz crystal resonators

McKenna

Newton

McHale

et al. 2001

Journal of Applied Physics

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Resonating quartz crystals can be used for sensing liquid properties by completely immersing one side of the crystal in a bulk liquid. The in-plane shearing motion of the crystal generates shear waves which are damped by a viscous liquid. Thus only a thin layer of fluid characterised by the penetration depth of the acoustic wave is sensed by a thickness shear mode resonator. Previous studies have shown that the finite lateral extent of the crystal results in the generation of compressional waves, which may cause deviations from the theoretical behavior predicted by a one-dimensional model. In this work, we report on a simultaneous optical and acoustic wave investigation of the quartz crystal resonator response to sessile microdroplets of water, which only wet a localized portion of the surface. The relationship between initial change in frequency and distance from the center of the crystal has been measured for the compressional wave generation regions of the 0 crystal using 2μl and 5μl droplets. For these volumes the initial heights do not represent integer multiples of a half of the acoustic wavelength and so are not expected to initially produce compressional wave resonance. A systematic study of the acoustic response to evaporating microdroplets of water has then been recorded for droplets deposited in the compressional wave generation regions of the crystals whilst simultaneously recording the top and side views by videomicroscopy. The data is compared to theoretically expected values of droplet height for constructive acoustic interference. Results are highly reproducible and there is good correlation between theory and experiment. PACS 43.35 Bf

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“…By contrast, in earlier treatments 1,3 it was assumed that the fluid was incompressible and an incomplete hydrodynamic equation was employed in which a pressure term was omitted. It was argued that the nonuniform tangential surface velocity of the crystal gave rise to a velocity in the fluid normal to the crystal surface.…”

Section: Simultaneous Generation Of S and P Wavesmentioning

confidence: 99%

“…This confirms and extends the experimental evidence given earlier. [1][2][3][4] Second, removing the restriction of incompressibility, and considering the full hydrodynamic equations for a viscoelastic fluid, the particle velocity in the fluid can be decomposed into component velocities transverse and normal to the crystal surface, which are compatible with the transverse shear and flexural modes excited at the crystal boundary. These components give rise, respectively, to S and P waves.…”

Section: Introductionmentioning

confidence: 99%

The coexistence of pressure waves in the operation of quartz-crystal shear-wave sensors

Reddy

Lewis

1998

Journal of Applied Physics

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It is demonstrated that an AT-cut quartz crystal driven in the thickness-shear-wave mode and typically used as a sensor to monitor the viscoelastic shear-wave properties of a fluid also produce longitudinal pressure waves. Unlike the shear wave, these waves are capable of long-range propagation through the fluid and of reflection at its boundaries, notably at an outer fluid-air interface. They introduce a component into the measured electrical impedance and resonance frequency shift of the crystal, which reflects the setting up of cyclic pressure-wave resonances in the fluid. This has important implications for the practical employment of these crystal as sensors. Under appropriate conditions, as demonstrated for water and n-octane, it is possible to determine the propagating properties of sound waves in a fluid simultaneously with the viscoelastic shear-wave properties. These experiments are supported by an analysis of the appropriate hydrodynamic equations for waves in the crystal-fluid system, which predicts electrical characteristics in close agreement with those found experimentally.

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Flow profile above a quartz crystal vibrating in liquid

Cited by 77 publications

References 7 publications

Quartz Crystal Microbalance for Bioanalytical Applications

Quartz Crystal Microbalance for Bioanalytical Applications

Compressional acoustic wave generation in microdroplets of water in contact with quartz crystal resonators

The coexistence of pressure waves in the operation of quartz-crystal shear-wave sensors

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