Biomedical Engineering Reference
In-Depth Information
(Figure 21.4). It comes with controller, oscillator electronics, crystal holder, and three quartz
crystals. An external frequency counter and precision voltmeter (not included) are needed to
complete the QCM-measurement setup. The QCM series measures the resonant frequency
and resistance of an 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 viscoelasticity of the material (film or liquid) in contact with the crystal's face [128].
As a gravimetric instrument, the QCM100 can measure mass ranging from micrograms
to fractions of a nanogram, with detection limits corresponding to submonolayers of atoms.
Measurement of resistance provides the opportunity to examine the viscosity and elasticity
of films and liquids at or near the crystal surface. This makes it feasible to observe confor-
mational changes, such as phase transitions, swelling, and cross-linking, in real time. The
electronics are specifically designed to handle heavy loads (up to 5 kW) making these
instruments ideal for studies involving glossy films and highly viscous liquids.
Applications of QCM100 instrument include the detection of virus capsids and bacteria,
mammalian cells, immunosensors, sorption sensors, antigen-antibody reactions, and
protein adsorption.
21.3.2.2 Packaged Interdigitated Microsensor Electrodes, (ABTECH Scientific, Inc.)
Central to ABTECH's suite of advanced products is its proprietary biochip technology. Based
on impedemetric detection of chemically amplified biochemical signals, ABTECH's biochip
technology gives rise to a suite of enzyme biochips (enzyme biosensors), immunodiagnostic
biochips (immunosensors), and DNA biochips (genosensors) that are well suited to the
physician's office, emergency room care, and the pathology lab markets (Figure 21.5) [129].
ABTECH is a biotechnology test and measurement company with interests in
point-of-con-
cern
biomedical diagnostics. Engaged in research, product development and commercializa-
tion of proprietary biosensor-based diagnostics, and monitoring technologies, ABTECH is
developing and marketing a suite of instrumented tests for the physician's office, emergency-
room care, and the pathology laboratory. ABTECH's mission is to deliver chemical and
biosensor-based test and measurement products that are cost-effective, reliable, and meet the
sensitivity, detection limits, and convenience requirements of the markets that they serve.
The Laboratory Products Group manufactures, markets, and sells research and devel-
opment products such as sensor devices, biochip substrates, transducers, electrodes,
FIGURE 21.4
QCM100
.
Quartz crystal microbalance ana-
lyzer. (From http://www.thinksrs.com/.
Accessed December 20, 2004.)
FIGURE 21.5
Packaged interdigitated microsensor elec-
trodes. (From www.abtechsci.com. Accessed
December 20, 2004.)
