Sensor Based on PZT Ceramic Resonator with Lateral Electric Field for Immunodetectionof Bacteria in the Conducting Aquatic Environment †

Abstract

A biological sensor for detection and identification of bacterial cells, including a resonator with a lateral electric field based on PZT ceramics was experimentally investigated. For bacterial immunodetection the frequency dependencies of the electric impedance of the sensor with a suspension of microbial cells were measured before and after adding the specific antibodies. It was found that the addition of specific antibodies to a suspension of microbial cells led to a significant change in these frequency dependencies due to the increase in the conductivity of suspension. The analysis of microbial cells was carried out in aqueous solutions with a conductivity of 4.5–1000 μS/cm, as well as in the tap and drinking water. The detection limit of microbial cells was found to be 103 cells/mL and the analysis time did not exceed 4 min. Experiments with non-specific antibodies were also carried out and it was shown that their addition to the cell suspension did not lead to a change in the analytical signal of the sensor. This confirms the ability to not only detect, but also identify bacterial cells in suspensions.

Multimode Design and Piezoelectric Substrate Anisotropy Use to Improve Performance of Acoustic Liquid Sensors

“…It is well-known that a change in electric conductivity of an adjacent medium located on a surface of a piezoelectric substrate produces a change in phase velocity and attenuation of any acoustic wave with nonzero coupling constant (Rayleigh [ 1 , 2 , 3 ], Love [ 3 ], Lamb [ 4 , 5 ], zero-order shear-horizontal [ 6 , 7 ], higher-order [ 8 ], slot [ 9 , 10 ], etc.). For most waves, the phase velocity decreases with conductivity monotonically, approaching its minimum value when tangential components of electric fields accompanying the wave are completely shorted [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ].…”

“…It is well-known that a change in electric conductivity of an adjacent medium located on a surface of a piezoelectric substrate produces a change in phase velocity and attenuation of any acoustic wave with nonzero coupling constant (Rayleigh [ 1 , 2 , 3 ], Love [ 3 ], Lamb [ 4 , 5 ], zero-order shear-horizontal [ 6 , 7 ], higher-order [ 8 ], slot [ 9 , 10 ], etc.). For most waves, the phase velocity decreases with conductivity monotonically, approaching its minimum value when tangential components of electric fields accompanying the wave are completely shorted [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. On the other hand, for particular cases of slightly inhomogeneous piezoactive surface acoustic waves with shear-horizontal polarization (Bleustein-Gulyaev and/or Love waves), an increase in conductivity of a substrate or conductive layer deposited on the substrate produces, first, an increase in phase velocity of the wave until some maximal value and then, a decrease in the velocity to some minimal value [ 11 , 12 ].…”

“…The acoustoelectric attenuation behaves similar for all types of acoustic waves: it increases for small conductivities, approaches some maximum for intermediate conductivities, and decreases to zero for large conductivities of the substrate or layer [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 ]. This property is due to the fact that at low conductivities, the layer behaves like dielectric, while at high conductivities it is more like an ideal conductor.…”