Performances and Limits of a Parallel Oscillator for Electrochemical Quartz Crystal Microbalances

Abstract

This paper describes a driving circuit for an electrochemical quartz crystal microbalance (EQCM) adapted to a wide range of applications. The oscillator is a Miller-type parallel oscillator using an operational transconductance amplifier (OTA). A theoretical study of the oscillating circuit led to the analytical expression of the microbalance frequency as well as to an overestimation of the error on the mass measurement. The reliability of the EQCM was then experimentally verified through electrochemical copper deposition and dissolution. The limit of operation of the EQCM was also investigated, both analytically and experimentally. This work shows that parallel oscillators using few electronic components allow a very reliable EQCM to be obtained for mass measurements on metallic films, even if they are highly damped.

Mass and charge balance in self-assembled multilayer films on gold. Measurements with optical reflectometry and quartz crystal microbalance

“…The microbalance frequency, f m , can be calculated by taking into account the parameters such as R m , L m , C m and also the parameters of the electronic circuit [46]. In our experimental conditions, we assume that the two frequencies, f BVD s and f m , are similar.…”

Multichannel QCM-Based System for Continuous Monitoring of Bacterial Biofilm Growth

“…In order to properly measure the QCM electrical impedance and its relevant parameters, the resonance frequency fs and the QCM series resistance at resonance Rm, many electronic circuits are found in literature based on network or impedance analysis [32]- [34], oscillators [35], [36], lock-in techniques [37]- [39], and impulse excitation and decay methods [40]. Most of these circuits have in common that are complex, expensive or they require manual compensation of the static capacitance Co effect.…”

QCM Technology in Biosensors

“…In practice, all the QCM sensor characterization techniques provide, among other relevant parameters, the resonance frequency shift of the sensor Eichelbaum et al, 1999): network or impedance analysis is used to sweep the resonance frequency range of the resonator and determine the maximum conductance frequency (Schröder et al, 2001;Doerner et al, 2003), which is almost equivalent to the motional series resonance frequency of the resonator-sensor; impulse excitation and decay method techniques are used to determine the series-resonance or the parallel-resonance frequency depending on the measuring set-up (Rodahl & Kasemo, 1996); oscillator techniques are used for a continuous monitoring of a frequency which corresponds to a specific phase shift of the sensor in the resonance bandwidth (Ehahoun et al, 2002;Barnes, 1992;Wessendorf, 1993;Borngräber et al, 2002;Martin et al, 1997), this frequency can be used, in many applications, as reference of the resonance frequency of the sensor; and the lock-in techniques, which can be considered as sophisticated oscillators, are designed for a continuous monitoring of the motional series resonance frequency or the maximum conductance frequency of the resonator-sensor (Arnau et al, 2002(Arnau et al, , 2007Ferrari et al, 2001Ferrari et al, , 2006Jakoby et al, 2005;Riesch & Jakoby 2007). In order to assure that the frequency shift is the only parameter of interest, a second parameter providing information of the constancy of the properties of liquid medium is of interest, mainly in piezoelectric biosensors; this parameter depends on the characterization system being: the maximum conductance or the conductance bandwidth in impedance analysis, the dissipation factor in decay methods and a voltage associated with the sensor damping in oscillator techniques The different characterization methods mentioned can be classified in two types: 1) those which passively interrogate the sensor, and 2) those in which the sensor forms part of the characterization system.…”