Study of acoustic Love wave devices for real time bacteriophage detection

Acoustic wave devices have shown their good potentialities for real time monitoring of immunoreactions. Different acoustic wave devices (BAW, SHAPM, Love waves) were described for applications in liquid medium. Love wave delay line structures (ST cut quartz substrate with interdigital transducers, SiO2 guiding layer) present several advantages, in particular, the pure shear horizontal polarisation adapted to liquid medium, and its very high sensitivity related to the wave confining in the thin guiding layer. In this paper an analytical method based on multilayer propagating structure is first presented: it allows us to estimate the Love wave phase velocity and then the mass loading effect sensitivity. A few theoretical results are exposed; they show that this theoretical analysis can allow to optimise physical parameters in order to conceive powerful devices for detection applications in liquid medium. As a model for virus or bacteria detection in liquids (drinking or bathing water, food, etc.), we design a model using M 13 bacteriophage. The first step is the anti-M13 antibody binding. By using a Labwindows CVI software, we can monitor in real time the graft of the anti-M13 antibody sensitive coating, as well as the detection of the M13 bacteriophages. Experimental results are exposed, analysed and discussed. Love waves sensors appear to be a powerful approach for immumodetection, as theoretically predicted. (C) 2003 Elsevier Science B.V. All rights reserved.