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The QCM200 Quartz Crystal Microbalance measures mass and viscosity
in processes occurring at or near surfaces, or within thin films.
This system includes a controller, crystal oscillator electronics,
crystal holder, three quartz crystals, and Windows / Mac software.
The instrument reads the resonant frequency and resistance of a
5 MHz, AT-cut quartz crystal. The resonant frequency changes as
a linear function of the mass of material deposited on the crystal
surface. The resistance at resonance changes with the viscosity
/ elasticity of the material (film or liquid) in contact with the
crystal surface.
As a gravimetric instrument, the QCM200 can measure mass ranging
from micrograms to fractions of a nanogram. Detection limits correspond
to submonolayers of atoms. Observations of conformational changes,
such as phase transitions, swelling, and cross-linking, can easily
be made.
Specifically designed to handle heavy loads (up to 5 kΩ),
the instruments will maintain oscillation in aqueous solutions contai
ning over 88 % glycerol (w/w %). It isideal for studies involving
lossy films and highly viscous liquids.
The QCM200 is a stand-alone instrument with a built-in frequency
counter and resistance meter. Series resonance frequency and resistance
are measured and displayed, and there is an analog output proportional
to frequency which can be used to interface with a potentiostat.
The QCM200 can be operated from the front panel or a PC using the
RS-232 interface. Windows and MacIntosh
software is provided for real-time data acquisition, display,
analysis and storage. Both frequency and resistance trends can be
viewed. User-tags are provided to time-stamp important events.
The stability and accuracy of the QCM200 are ideal for most experiments.
For special applications requiring optimum long-term frequency stability,
a precision timebase, such as the FS725 Rubidium Frequency Standard,
can be connected to the external 10 MHz input.
QCM Electronics
A unique automatic gain control circuit provides the quartz crystal
with the required signal amplitude to overcome viscoelastic losses
and achieve series resonance. It also monitors the energy dissipated
by the sensor, which is used to determine the series resistance
of the crystal. The controller provides power to the crystal oscillator
electronics, and includes a potentiometer for canceling shunt capacitance.
Proper capacitance cancellation is required to assure true series
resonance operation of the crystal oscillator, and to eliminate
frequency and resistance errors.
In the QCM200, the digital controller also contains a frequency
counter with 0.01 Hz resolution for accurate frequency measurements,
and a resistance meter with 5 digits of resolution covering a range
of 0 to 5000 Ω.
Crystals, Holder and Flow Cell
The QCM200 uses a 5 MHz, 1" diameter, AT-cut quartz crystal
wafer with circular electrodes on both sides. Crystals are available
in a variety of materials. The crystal holder is a rugged, compact,
easy to use fixture. The holder and all crystals may be used in
liquid or gas environments.
An optional axial flow cell adapter attaches to the standard crystal
holder. This provides an easy way of interfacing the QCM to a flow
injection analysis system.
EQCM
For EQCM applications, an analog output proportional to frequency
shift may be directly connected to a potentiostat or galvanostat.
Only the front-surface electrode of the crystal is exposed to the
solution. This electrode is also transformer isolated, as required
for EQCM operation.
The figure below illustrates a typical EQCM experiment. The frequency
analog output of the QCM controller is connected to the potentiostat
A/D input. The potentiostat digitizes the voltage, and it's software
displays relative frequency changes synchronous with the electrochemical
data. The versatile QCM200 can be easily integrated into any custom
5 MHz crystal based EQCM setup.
In the Lab
The QCM200 is a valuable research tools for applications ranging
from pure surface science to biochemistry. Quartz crystals can be
pre-coated with any thin film material including organic polymers,
hydrogels, composites, ceramics, biomolecules, bacteria and living
cells. This provides unlimited potential for the development of
novel gas and biological sensors.
The quartz crystal microbalance is an essential addition to any
biological laboratory. The data 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 biological interactions.
QCM200 Software
A Windows/Mac software program
is included to facilitate remote operation and simplify data acquisition.
Applications
Selected Literature
Citations of SRS QCM100/200
Immunosensors
Sorption sensors
Moisture analyzers
Particulate monitors
Contamination monitors
Electrovalency measurements
Hydrogen absorption on metal films
Bubble formation
Redox and conductive polymer research
Double-layer characterization
Corrosion studies
Surface oxidation
DNA and RNA hybridization studies
Antigen-antibody reactions
Protein adsorption
Detection of virus capsids, bacteria, mammalian cells
Biofouling and antifouling
Biomembranes and biomaterials
Protein-protein interactions
Self-assembled monolayers (SAMs)
Molecularly imprinted polymers (MIPs)
Langmuir/Langmuir-Blodgett films
Laser ablation, desorption and breakdown studies
MEMS nanomaterials
Intelligent biomaterials
Demo Video of QCM Probe Assembly
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