Electroacoustic Biosensor Systems for Evaluating Antibiotic Action on Microbial Cells.

Antibiotics are widely used to treat infectious diseases. This leads to the presence of antibiotics and their metabolic products in the ecosystem, especially in aquatic environments. In many countries, the growth of pathogen resistance to antibiotics is considered a threat to national security.

Microwave resonator-based sensor system for specific antibody detection.

An antibody-detecting sensor is described that is based on a microwave electrodynamic resonator. A polystyrene film with immobilized bacteria deposited on a lithium niobate plate was placed at one end of the resonator and was used as the sensing element. The second end was electrically shorted.

Sensor System Based on a Piezoelectric Resonator with a Lateral Electric Field for Virus Diagnostics.

A sensor system based on a piezoelectric resonator with a lateral electric field in the frequency range 6-7 MHz of the electric field for virus detection is described. Through use of the transmissible virus causing gastroenteritis in pigs and specific antibodies, the possibility of detecting the virus in suspension in real time was determined. It was found that the frequency dependence of the real and imaginary parts of the electrical impedance of such a resonator loaded with a virus suspension changes significantly after the addition of specific antibodies to the suspension.

A new liquid sensor based on a piezoelectric resonator with a radial electric field.

The possibility of development a liquid sensor based on a piezoelectric resonator with radial concentric electrodes is shown. The specified resonator has a large number of resonance peaks corresponding to different vibrational modes. The influence of two types of liquid container with distilled water on the resonance characteristics of these vibrational modes is experimentally investigated.

Prospects for the Use of Gold Nanoparticles to Increase the Sensitivity of an Acoustic Sensor in the Detection of Microbial Cells.

The interaction of microbial cells with antibody-gold nanoparticle conjugates in conductive suspensions was experimentally studied by using an acoustic slot-mode sensor. The sensor consisted of a piezoelectric plate with a propagating acoustic wave and a liquid container located above this plate with a given gap. An analysis of the measured parameters of the sensor revealed that the specific interaction of bacterial cells with the conjugates led to a stronger change in the sensor output signal than the specific interaction of bacterial cells with antibodies.

Evaluation of Elastic Properties and Conductivity of Chitosan Acetate Films in Ammonia and Water Vapors Using Acoustic Resonators.

Novel bio-materials, like chitosan and its derivatives, appeal to finding a new niche in room temperature gas sensors, demonstrating not only a chemoresistive response, but also changes in mechanical impedance due to vapor adsorption. We determined the coefficients of elasticity and viscosity of chitosan acetate films in air, ammonia, and water vapors by acoustic spectroscopy. The measurements were carried out while using a resonator with a longitudinal electric field at the different concentrations of ammonia (100-1600 ppm) and air humidity (20-60%).

Analysis of Microbial Cell Viability in a Liquid Using an Acoustic Sensor.

A method was developed for the rapid analysis and evaluation of the viability of bacteriophage-infected Escherichia coli (E.coli) XL-1 directly in a conducting suspension by using a slot-mode sensor. The method is based on recording the changes in the depth and frequency of resonant absorption peaks in the frequency dependence of the insertion loss of the sensor before and after the biologic interaction of E.

Acoustic waves in a structure containing two piezoelectric plates separated by an air (vacuum) gap.

This paper presents experimental results for the characteristics of acoustic waves propagating in a structure containing two parallel piezoelectric plates (I and II) separated by an air gap. Plate I, made of Y-X lithium niobate, contained two interdigital transducers that excited and received an acoustic wave with shear-horizontal polarization. Piezoelectric plate II, made of lithium niobate, was placed above and between the transducers, separated by a fixed gap.

Transmission of surface acoustic waves through the interface based on discontinuity of electrical boundary conditions on surface of potassium niobate.

This paper presents theoretical investigation of the propagation of surface acoustic waves (SAWs) across the boundary between metallized (electrically shorted) and unmetallized (electrically open) regions on the surface of potassium niobate crystals. Potassium niobate is a very strong piezoelectric material and has the interesting property that only one type of SAW, namely a Rayleigh wave, can exist on unmetallized surface, where as two types of SAWs, namely Rayleigh and Bleustein-Gulyaev (BG), can exist on a metallized surface. Analysis shows that the Rayleigh wave propagates through the interface with very little change in amplitude or polarization.