Why QCM-D Is the Preferred Real-Time Method for Surface Analysis Our expertise

It has always been the case that a whole series of processes need to be carried out. First, researchers must figure out what surface properties are needed. Second, how to modify and characterize the surface properties. Several tests need to be done to confirm that we have the right surface properties that we have planned.

Going the Quartz Crystal Way

Quartz crystal microbalance with dissipation monitoring (QCM-D) is a powerful method for monitoring of molecular interactions at surfaces and interfaces and thin film properties

Measuring changes of two parameters, the resonance frequency, Δf, and the energy dissipation, ΔD, of an oscillating quartz crystal disk, this surface sensitive analytical technique can provide information on mass, thickness, and viscoelastic properties of layers at the sensor surface. The method can, for example, be used to systematically study the adsorption behavior of molecules of interest to relevant surfaces in a wide range of solution mixtures.

QCM-D analysis provides a fundamental understanding of processes and the ability to optimize products and processes for authentic conditions.

The QCM-D technology was developed and commercialized in the 1990s by scientists at Chalmers University of Technology in Sweden. Since then, the QCM-D community has grown along with interest in the capabilities of this technology. Today, the instruments are used in research facilities around the world in a wide range of application areas such as in pharmaceuticals, biotechnology, energy, polymers, electronics, and many others.

Figure 1: Frequency (blue) and dissipation (red) shifts for antibody assay construction: immobilization of coupling molecules, streptavidin, and biotinylated protein A, followed by capture of anti-BSA and antigen binding, BSA.

Versatile Conditions

QCM-D can be used under various experimental conditions, such as in controlled humidity, controlled pressure, in harsh solvents, and in the gas phase. The hardware also allows for combination and simultaneous measurements with complementary methods such as electrochemistry, ellipsometry, and microscopy.

The detection range is ~1 Å to 1 um, depending on the layer properties, which allows for molecules such as biomolecules, surfactants, polymers, nanoparticles, cells, and other structures in the same size range to be studied.

Examples of processes that can be analyzed with QCM-D:

• Adsorption / Desorption
• Binding / Release
• Buildup/Degradation
• Crosslinking
• Swelling / Collapse

Figure 2: Schematic illustration of processes that can be studied with QCM-D.
(Top) Molecular adsorption, desorption, and binding
(Middle) Soil swelling and removal
(Bottom) Crosslinking or collapse of polymer brush