Gigahertz surface acoustic wave probe for chemical analysis

Stevenson, Alice; Mehta, Hiren; Sethi, R. S.; Cheran, Larisa-Emilia; Thompson, Michael; Davies, Ian; Lowe, Christopher R.

doi:10.1039/b107062b

Cited by 12 publications

(8 citation statements)

References 33 publications

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“…For the development of an improved arrangement for biosensing, it is useful to use a time-of-flight resolved information system in order to identify spurious reflections, discriminate between different acoustic modes and to aid the optimization of the sensitivity of devices. Examples of shear horizontal SAW pulsed analysis have been already reported (Chung et al 1998, Stevenson et al 2001, Newton et al 2001b. In this work, we extend the application of a pulse mode measurement system to utilize LiTaO 3 devices and give rapid amplitude and phase information for biosensing experiments.…”

Section: Introductionmentioning

confidence: 99%

Pulse mode shear horizontal-surface acoustic wave (SH-SAW) system for liquid based sensing applications

Martin

Newton

McHale

et al. 2004

Biosensors and Bioelectronics

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In this work we describe a novel pulse mode shear horizontal surface acoustic wave (SH-SAW) polymer coated biosensor that monitors rapid changes in both amplitude and phase. The SH-SAW sensors were fabricated on 36 ο rotated Y-cut X propagating Lithium Tantalate (36 YX.LT). The sensitivity of the device to both mass loading and visco-elastic effects may be increased by using a thin guiding layer of cross-linked polymer. Two acoustic modes are excited by the electrodes in this crystalline direction. Metallisation of the propagation path of the 36 YX.LT devices allows the two modes to be discriminated. Successive polymer coatings resulted in the observation of resonant conditions in both modes as the layer thickness was increased.Using the 36 YX.LT devices, we have investigated the application of a novel pulse P r e -P r i n t mode system by sensing a sequence of deposition and removal of a biological layer consisting of vesicles of the phospholipid POPC. A continuous wave system was used to verify the accuracy of the pulse mode system by sensing a series of Poly(ethylene glycol) (PEG) solutions. The data clearly demonstrates the ability of the 36 YX.LT pulse mode system to provide rapid measurements of both amplitude and phase for biosensing applications.

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Section: Introductionmentioning

confidence: 99%

Pulse mode shear horizontal-surface acoustic wave (SH-SAW) system for liquid based sensing applications

Martin

Newton

McHale

et al. 2004

Biosensors and Bioelectronics

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“…This frequency dependency principle has been of great value to optical absorption spectroscopy techniques, although acoustic systems have never had sufficient bandwidth or convenience for molecular spectra to be generated and discovered in the first place. Attempts have been made with surface acoustic wave devices to recover frequency dependent information by using multiple transducers on a single device 13 or by making use of the non-linear properties of the crystal to generate harmonics ten times the frequency of the fundamental; 15 however, the intervals between the harmonics are too widely spaced to discriminate patterns. The difficulty in generating and detecting the higher harmonics at appropriate frequency intervals has also been investigated for acoustic resonators and accompanied with theoretical analysis of the relationship between predicted harmonic patterns and the measured variations in acoustic amplitude and frequency.…”

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confidence: 99%

The acoustic spectrophonometer: A novel bioanalytical technique based on multifrequency acoustic devices

Stevenson

Araya-Kleinsteuber

Sethi

et al. 2003

Analyst

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A measurement technique similar to optical absorption spectroscopy but based on evanescent acoustic waves is described in this paper. This format employs a planar spiral coil to vibrate a single crystal of quartz from 6 to 400 MHz, in order to measure multifrequency acoustic spectra. Consistency with the defined Sauerbrey and Kanazawa terms K1 and K2 when applied to multiple frequencies was found for these specific operating conditions in terms of a significant fit between the measured and calculated values: For an IgG surface density of 13.5 ng mm(-2) the measured value of K1 is 22.5 x 10(-6) and the calculated value is 20.4 x 10(-6), whilst for glycerol viscous loadings of 5.131 cP the measured value of K2 is 0.47 and the calculated value is 0.54. Thus for these specific surface loadings the multifrequency data fits to the predictions of the Sauerbrey model to within 10% and to Kanazawa model within 13%. However collective frequency shifts for 5.131 cP solutions of sucrose, dextran and glucose were found to exhibit an unanticipated additional variability (R2 < 0.4) with frequency, but retained a square root of frequency dependency within a factor 2 of the interpolated K2 values. The response to the 5.131 cP dextran solution was found to be significantly below the other isoviscous solutions, with a substantially reduced frequency shift and K2 value than would be expected from its bulk viscosity. In comparison with these viscous solutions, IgG protein films consistently produced linear frequency shifts with little scatter (R2 > 0.96) that were proportional to the operating frequency, and fully consistent with the Sauerbrey model under these specific conditions. A t-test value of 14.52 was calculated from the variance and mean of the two groups, and demonstrates that the acoustic spectrophonometer can be used to distinguish between the acoustic impedance characteristics of two chemical systems that are not clearly differentiable at a single operating frequency.

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“…Although high frequencies ͑small wavelengths͒, particularly those above 1 GHz, are essential for increasing sensitivity application of them is rarely reported. 5,12 One reason is the difficulty to fabricate GHz SAW devices. For example, in order to achieve operating frequency of 5 GHz with single finger interdigital transducers ͑IDTs͒ with two electrodes per wavelength, with equal widths for the electrodes and gaps and a phase velocity of 3000 m/s, structural dimensions of roughly 0.15 m have to be fabricated.…”

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confidence: 99%

“…Because standard optical photolithography is limited to about 0.5 m, the IDTs are usually operated at higher harmonics of fundamental frequency. 12 However, the efficiency of SAW excitation at higher harmonics in conventional device structures rapidly decreases so that their operation rarely reaches several GHz.…”

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confidence: 99%

Multimode and multifrequency gigahertz surface acoustic wave sensors

Seidel

Hesjedal

2004

Applied Physics Letters

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A simple surface acoustic wave sensor system is presented that combines the advantages of multifrequency/multimode operation and GHz frequencies in a single acoustic device structure. Analyzing multiple frequencies and modes is the basis for the multicomponent analysis of gases and liquids. The sensor system is based on floating electrode unidirectional transducers that allow efficient excitation of two modes and up to 48 harmonics ͑or 5 GHz͒. It can be fabricated without the need of costly nanofabrication techniques. Higher sensor frequencies are advantageous as the sensitivity increases with the frequency. We tested the basic operation of our sensor system by applying it to humidity sensing without a sensitive layer.

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Gigahertz surface acoustic wave probe for chemical analysis

Abstract: A study of the effect of pH, solvent system, cone potential and the addition of crown ethers on the formation of the monensin protonated parent ion in electrospray mass spectrometry-Norberto P.

Cited by 12 publications

References 33 publications

Pulse mode shear horizontal-surface acoustic wave (SH-SAW) system for liquid based sensing applications

Pulse mode shear horizontal-surface acoustic wave (SH-SAW) system for liquid based sensing applications

The acoustic spectrophonometer: A novel bioanalytical technique based on multifrequency acoustic devices

Multimode and multifrequency gigahertz surface acoustic wave sensors

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