Quartz Crystal Microbalance - QCM200 (2024)

QCM200 Quartz Crystal Microbalance

The QCM200 Quartz Crystal Microbalance measures mass and viscosity in processes occurring at or near surfaces, or within thinfilms. Thissystem includes a controller, crystal oscillator electronics, crystal holder, three quartz crystals, and Windowssoftware.

The instrument reads the resonant frequency and resistance of a 5MHz, AT-cut quartzcrystal. Theresonant frequency changes as a linear function of the mass of material deposited on the crystalsurface. Theresistance at resonance changes with the viscosity / elasticity of the material (film or liquid) in contact with the crystalsurface.

As a gravimetric instrument, the QCM200 can measure mass ranging from micrograms to fractions of ananogram. Detection limits correspond to submonolayers of atoms. Observations of conformational changes, such as phase transitions, swelling, and cross-linking, can easily bemade.

Crystal Holder with Flow Cell X Crystal Holder with Flow Cell

Specifically designed to handle heavy loads (up to 5kΩ), the instruments will lossy films and highly viscousliquids.

The QCM200 is a stand-alone instrument with a built-in frequency counter and resistancemeter. Seriesresonance frequency and resistance are measured and displayed, and there is an analog output proportional to frequency which can be used to interface with apotentiostat. TheQCM200 can be operated from the front panel or a PC using the RS-232 interface. Windowssoftware is provided for real-time data acquisition, display, analysis and storage. Bothfrequency and resistance trends can be viewed. User-tags are provided to time-stamp importantevents.

The stability and accuracy of the QCM200 are ideal for mostexperiments. Forspecial applications requiring optimum long-term frequency stability, a precision timebase, such as the FS725 Rubidium Frequency Standard, can be connected to the external 10MHzinput.

QCM Electronics

A unique automatic gain control circuit provides the quartz crystal with the required signal amplitude to overcome viscoelastic losses and achieve seriesresonance. Italso monitors the energy dissipated by the sensor, which is used to determine the series resistance of the crystal. Thecontroller provides power to the crystal oscillator electronics, and includes a potentiometer for canceling shuntcapacitance. Propercapacitance cancellation is required to assure true series resonance operation of the crystal oscillator, and to eliminate frequency and resistanceerrors.

In the QCM200, the digital controller also contains a frequency counter with 0.01Hz resolution for accurate frequency measurements, and a resistance meter with 5digits of resolution covering a range of 0 to5000Ω.

Crystals, Holder and Flow Cell

The QCM200 uses a 5MHz, 1" diameter, AT-cut quartz crystal wafer with circular electrodes on bothsides. Crystalsare available in a variety ofmaterials. The crystal holder is a rugged, compact, easy to use fixture. Theholder and all crystals may be used in liquid or gasenvironments.

An optional axial flow cell adapter attaches to the standard crystalholder. Thisprovides an easy way of interfacing the QCM to a flow injection analysissystem.

EQCM

EQCM X EQCM

For EQCM applications, an analog output proportional to frequency shift may be directly connected to a potentiostat orgalvanostat. Onlythe front-surface electrode of the crystal is exposed to thesolution. Thiselectrode is also transformer isolated, as required for EQCMoperation.

The figure below illustrates a typical EQCMexperiment. Thefrequency analog output of the QCM controller is connected to the potentiostat A/Dinput. The potentiostat digitizes the voltage, and it's software displays relative frequency changes synchronous with the electrochemicaldata. Theversatile QCM200 can be easily integrated into any custom 5MHz crystal based EQCMsetup.

In the Lab

The QCM200 is a valuable research tools for applications ranging from pure surface science tobiochemistry. Quartzcrystals can be pre-coated with any thin film material including organic polymers, hydrogels, composites, ceramics, biomolecules, bacteria and living cells. Thisprovides unlimited potential for the development of novel gas and biologicalsensors.

The quartz crystal microbalance is an essential addition to any biologicallaboratory. Thedata from a QCM perfectly complements that obtained from other techniques, such as surface plasmon resonance (SPR) and atomic force microscopy (AFM), aiding in the analysis of complex biologicalinteractions.

Data Acquisition Software X Data Acquisition Software

QCM200 Software

A Windows software program is included to facilitate remote operation and simplify dataacquisition.