Method and device for nanogravimetry in fluid media using piezoelectric resonators

摘要

The invention relates to a method, to a device for electronic characterization, and to a measurement cell and support for monitoring a chemical or physical process with results that can be assessed in terms of the weight variation of a coating deposited on a piezoelectric sensor, exposed to a fluid medium with stable physical properties. The invention uses the deduction of an analytic expression establishing a simple connection between the phase variation of a fixed-frequency signal, which queries the piezoelectric resonator, and the variation in the bulk density of the coating. The invention is suitable for implementations that use piezoelectric resonators for characterizing biochemical and electrochemical processes, such as, inter alia: piezoelectric biosensors and immunosensors, process and material characterization by AC electrogravimetry, detection of dissolved chemical or biological substances.

主权项

1. A method for determining a mass surface density change of a coating deposited on a piezoelectric resonator exposed to a fluid medium, the resonator acting as a sensor connected to a circuit to which a test signal is applied, and the fluid medium being such that physical characteristics remain stable during an experimental process, the method comprising:
a) selecting the frequency of a test signal substantially equal to the dynamic series resonant frequency of the resonator in an initial state of the resonator, taking such state as a reference; b) measuring the values of two voltage signals, one of which establishes the phase reference of the sensor and the other one establishes the reference of the loss level thereof; c) monitoring the voltage values taken as a reference in said measuring operation during the experimental process that is to be monitored; d) verifying that the value of the loss reference voltage of the sensor does not essentially change during the measurement process; e) correcting the value of the frequency of the test signal during the experimental process to be monitored, in the event that the signal provided by the measurement of the phase variation has been deviated above or below a predetermined value based on the features of the experiment, the voltage value obtained as a phase reference of the sensor in said step b), until the voltage signal that provides the measurement of the phase variation again has the same value as that obtained by phase reference of the sensor in said step b), or its difference in absolute value is less than a certain predetermined number depending on the characteristics of the experiment; and f) obtaining the mass surface density change on the coating during the experimental process from the variations of the voltage signal that provides the measurement of the phase variation by calculating the mass surface density change as a function of the phase variation of the voltage signal that provides the measurement of the phase variation.