QCM-I ‘Impedance measurement’ of quartz up to 80 MHz – a fully-fledged and comparable alternative to QCM-D technology
QCM-I ‘Impedance measurement’ of quartz up to 80 MHz – a fully-fledged and comparable alternative to QCM-D technology
The QCM-I technique of ‘impedance measurement’ is a well-established and sensitive measurement method for determining the viscoelastic properties of very thin, hydrated layers (polymers, biological samples or biofilms) at an electrode interface in an electrolyte, in real time and without the need for additional markers.Using a QCM-I measuring device, the impedance of the quartz crystal sensor is measured with a network analyser to determine both the resonance frequency and the bandwidth (full width at half maximum – FWHM) of the resonance spectrum. This is carried out across several frequency ranges, both at the fundamental resonance frequency (5 MHz) of the quartz crystal and at the higher harmonics (15 MHz, 25 MHz, 35 MHz, etc.).
The change in mass of the hydrated mass coupled to the sensor surface can then be measured, via a proportionality factor, with the frequency change down to one billionth of a gram. The FWHM of the resonance frequency peak in the quartz’s EIS spectrum is directly related to the energy dissipation at the interface and provides information on the viscoelastic properties and structure of the adsorbed layer or on the viscosity of the liquid.
Product Description
The QCM-I system is a highly sensitive mass sensor that measures the resonance frequency change and the resonance frequency quality of a quartz crystal resonator and thus, as a biosensor without additional markers, makes it possible to measure “wet masses” near the sensor surface and to characterise them with regard to density, shear modulus and viscosity of the adsorbed layer for an accurate layer thickness determination including layer properties of the biological sample or sample polymer for a wide range of applications.
The measuring principle is based on the impedance analysis of the quartz crystal. The resonance frequency and the bandwidth or resonance frequency quality are determined. The bandwidth or bandwidth at half maximum (FWHM) is directly correlated to the quality factor (Q), which by definition is the reciprocal of the dissipation (D) or power loss known from the QCM-D technique.
In the case of biological samples or sample polymers, we are not dealing with materials that adhere rigidly to the quartz crystal resonator, but with samples that cannot follow part of the shear movement of the quartz and are therefore lost as dissipation (D). As a result, incorrect results are obtained under the assumption of a rigid coating and the Sauerbrey approximation that the coating material and sensor have approximately the same density.
To close this gap, the QCM-D technique, in which the amplitude of the recorded decay of the oscillation is calculated from the decay time (t) and frequency (ƒ), was used to obtain the dimensionless dissipation (D) or power loss.
Viscoelastic properties of polymer layers can be described with this value D, which corresponds to the reciprocal value of the quality factor Q. This quality factor Q in turn corresponds to a simplified quotient of the energy that could be stored in the oscillating system compared to the energy that was lost.
The ability to measure not only the fundamental frequency together with D, but also at higher harmonics of the fundamental frequency makes it possible to calculate not only the mass of the coating, but also its viscoelastic properties using a mechanical continuum model (Voigt-Kelvin model).
In contrast to the QCM-D measurement principle, the QCM-I measurement principle uses impedance analysis as a readout technique. In this case, impedance spectra are recorded for fundamental and overtone frequencies. These spectra are fitted with the parameters FWHM (Full Width at Half Maximum) and resonance frequency ƒ. The equivalent circuit model developed by Johannsmann showed that the DFWHM/Dƒ formula can be linked to the viscoelastic properties of the crystal and its surface layers, so that viscoelastic analysis is also possible using impedance measurement technology. The dissipation can be expressed by the FWHM parameter derived from the impedance analysis.
It was also shown that the impedance spectrum of the QCM-I measurement principle can be obtained from the ozillation decay curve of the QCM-D measurement principle by Fourier transformation, which makes the two parameters of D obtained from the different measurement principles equivalent.
It could even be shown that data obtained from the QCM-D measurement principle by equivalent circuit diagrams can lead to viscoelastic properties in the same way as the data obtained with the QCM-I measurement principle by the Voigt-Kelvin model.
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Specifications
FREQUENCY RESOLUTION:200 mHz (in electrolyte)
‘DISSIPATION’ RESOLUTION:
10⁻⁷
MASS RESOLUTION:
≤ 1
ng·cm⁻²
SENSOR:
AT-SiO₂ (OD 14 mm; fundamental resonance frequency = 5 MHz)
CHANNELS:
1 –
4
FREQUENCY
RANGE:
1 MHz – 80 MHz (up to the 13th harmonic for the 5 MHz sensor)
TEMPERATURE CONTROL:
4°C – 80 °C with ± 0.02 K
MATERIALS IN CONTACT
WITH THE MEDIA:
PTFE, PEEK, SS; VITON or KALREZ
POWER SUPPLY:
DC power supply with AC/DC transformer (100 V – 240 V at 50 Hz – 60 Hz)
VOLUME
DOSING:
Sample injection via external syringe or peristaltic pump unit (manual or controlled by BioSense software)
Rheodyne Model 9725 manual injection valve
Rheodyne MX Series semi-automatic switching valve.
An external autosampler unit is available as an
option
VOLUME
“FLOW CELL”:
approx. 40 µl
TYPICAL VOLUME FLOW RATES:
0.01 µl·min⁻¹ to 35 ml·min⁻¹ with external syringe pump (1 ml – 60 ml syringe size)
ADJUSTABLE
SAMPLE VOLUME:
1 µl – 2000 µl (depending on the installed loop volume)
Options and Accessories
• QCM-I glove box
• QSH-014 – QCM sensor holder with flow cell for 14 mm crystals – 974-00001
• O-ring kit for QSH-014 — 1 x 12x2mm silicone with gold wires, 3 x 12x2mm Viton – 974-00016
• PCB kit for QSH-014 with M2.5 screws – 974-00020
• Nut and ferrule set (5 sets of P259 flangeless ferrules and P252 nuts 1/4-28 flat bottom) – 974-00022
• Nut and ferrule set (5 sets of M650 flangeless ferrules and M644-03 nuts 6-40 flat bottom) – 974-00023
• Luer (female) connector with 1/4-28 union – 974-00024
• Perifit for connecting Teflon tubing to Tygon pump tubing, PEEK, fits nut MV-SP-007 – 974-00025
• FEP tubing (OD 1/16”, ID 0.03”, 10ft long) – 974-00026
• RF cable kit (200 mm long) to connect remote QCM sensor holder to main unit – 974-00027
• Cleaning holder to hold six (6) crystals, PEEK – 974-00028
• RF calibration kit for service purposes – 974-00029
• Calibration kit for training purposes – 974-00030
• Test electrical cable with 1 mm banana plug and 2 mm banana plug, silicone, 500 mm long – 974-00031
• Test electrical cable with 1 mm banana socket and 4 mm banana socket, silicone, 500 mm long – 974-00032
• Test electrical cable with 2 mm banana plug and 2 mm banana socket, silicone, 500 mm long – 974-00033
• Test electrical cable with 2mm banana plug and 4mm banana socket, silicone, 500mm long – 974-00034
• QSH-dip – QCM sensor holder for dip-in applications – 974-00003
• QSH-vac – QCM sensor holder for vacuum applications – 974-00004
• QSH-HT-HP – QCM sensor holder for high-temperature and high-pressure applications – 974-00005
• QSH-ext – extension RF cable assembly for remote QCM sensor holder – 974-00006
• QMH – QCM measuring head with temperature control – 974-00007
• UVO – mini UV ozone cleaner – 974-00008
• PSC-10 – plasma surface cleaner – 974-00009
• SYR-2 – two-channel syringe pump – 974-00010
• SASV – semi-automatic switching valve with BioSense 3.xx software module – 974-00011
• BioSense – BioSense 3.xx software, second user licence – 974-00012
• BioSense upgrade – BioSense 2.xx software upgrade to BioSense 3.xx – 974-00013
• BioSense EC upgrade – BioSense 3.xx software upgrade to BioSense EC 3.xx – 974-00014
• Customer training – customer training via the internet (max. 4 hours) on how to use the QCM and BioSense – 974-00015
Applications
– Basics of Electrochemical Impedance Spectroscopy [Link AN 5657]
– Equivalent Circuit Modelling in EIS [Link AN 5658]
– Comparison of Corrosion Rates Calculated by EFM, LPR and EIS [Link AN 5660]
– Tsujikawa-Hisamatsu-Electrochemical (THE) Method for Crevice Corrosion Repassivation Potentials [Link AN 5671]
– Basics of Electrochemical Corrosion Measurements [Link AN 5677]
– EIS Measurement of a Very Low Impedance Lithium Ion Battery [Link AN 5682]
– Steps for Creating an Application Using GamryCOM [Link AN 5687]
– Measuring the Impedance of Your Reference Electrode [Link AN 5697]
– Testing Supercapacitors: Part 1 – CV, EIS and Leakage Current [Link AN 5710]
– Demystifying Transmission Lines: What are they? Why are they useful? [Link AN 5711]
– Basics of a Quartz Crystal Microbalance [Link AN 5717]
– OptiEIS™ – A Multisine Implementation [Link AN 5718]
– Testing Supercapacitors: Part 2 – CCD and Stacks [Link AN 5724]
– Calibration of an Au-coated Quartz Crystal [Link AN 5727]
– EQCM Investigations of a Thin Polymer Film [Link AN 5728]
– Measuring Surface-Related Currents using Digital Staircase Voltammetry [Link AN 5731]
– Testing Supercapacitors: Part 3 – Electrochemical Impedance Spectroscopy [Link AN 5732]
– Monitoring Layer-by-Layer Assembly of Polyelectrolyte Film using a Quartz Crystal Microbalance [Link AN 5736]
– Characterisation of a Supercapacitor using an Electrochemical Quartz Crystal Microbalance [Link AN 5737]
– Extending Electrochemical Quartz Crystal Microbalance Techniques to Macroscale Electrodes [Link AN 5746]
– How Cabling and Signal Amplitudes Affect EIS Results [Link AN 5747]
– Testing Lithium-Ion Batteries [Link AN 5748]
– The Art of Electrochemistry in an Autoclave [Link AN 5751]
– Getting Started With Your First Experiment: DC105 Corrosion Techniques – Polarisation Resistance [Link AN 5754]
– Getting Started With Your First Experiment: EIS300 Electrochemical Impedance Techniques – Potentiostatic Electrochemical Impedance Spectroscopy [Link AN 5755]
– The Implementation of Transmission Lines Using Generalised Circuit Blocks [Link AN 5757]
– Use of Transmission Lines for Electrochemical Impedance Spectroscopy [Link AN 5758]
– A Snapshot of Electrochemical Impedance Spectroscopy [Link AN 5759]
– Determination of the correct value of Cdl from the impedance results fitted by commercially available software [Link AN 5760]
– EIS of Organic Coatings and Paints [Link AN 5763]
