Quartz Crystal Microbalance Mass Research Articles

Exploration of the Mass Sensitivity of Quartz Crystal Microbalance under Overtone Modes Using Electrodeposition Method.

With the in-depth application of quartz crystal microbalance (QCM) sensors in the fields of science and engineering, there is an urgent need for QCM sensors with high mass sensitivity. The mass sensitivity of a QCM is closely related to its resonance frequency, and the high resonance frequency leads to improve its mass sensitivity. However, the resonance frequency of a QCM resonator cannot be increased all the time due to the fragility of quartz wafer and the limits of energy trapping effect. Few studies are associated with mass sensitivity of a QCM resonator under overtone modes. Herein, we propose to make a QCM resonator work in its n-th overtone (n = 3, 5, 7, 9 in this study) mode to increase its resonance frequency during operating. Thereby, the purpose of improving QCM mass sensitivity is achieved, and the mass sensitivity of a QCM working in the n-th overtone mode can be called as n-th overtone mass sensitivity. Then, the n-th overtone mass sensitivity of a QCM sensor is measured by an electrodeposition method. The experimental results show that the n-th overtone mass sensitivity of a QCM is a bit more than n times that of the fundamental mass sensitivity, and it is consistent with the theoretical calculation results. The application of overtone mass sensitivity will greatly improve the sensitivity of QCM sensors, which is very attractive for the research fields that require QCM sensors with high sensitivity.

Analysis of the Uniformization of the QCM Mass Sensitivity Distribution through a Dot Multiring Electrode Structure.

In this paper, to improve the uniformity of the quartz crystal microbalance (QCM) mass sensitivity distribution, the effect of the size of dot ring electrode and dot double-ring electrode on the mass sensitivity distribution is analyzed theoretically from the perspective of the electrode width ratio, the width of the partially electroded region, and the electrode thickness. Within a certain range of electrode thickness, there is an optimum electrode width ratio to obtain a relatively uniform distribution. As long as the width of the partially electroded region is not too large or too small, it has no significant influence on the uniformity of the mass sensitivity of the optimum electrode size. The dot triple-ring electrode is proposed and the comparison of the uniformity between the three electrode structures indicates that more division of the electrode region can greatly improve the uniformity of the mass sensitivity distribution. This research provides a new direction for the uniformization of QCM mass sensitivity distribution.

Reversible oxide formation during cycling of Si anodes

Silicon is a hot candidate for battery anodes as its theoretical storage capacity is almost ten times larger than that of graphite. Volume expansion and kinetic limitations require the nanostructuring in particles, wires or thin films. One feature that still puzzles researchers is the solid electrolyte interface (SEI). Here we use an electrochemical quartz crystal microbalance (QCM) to inspect in-situ SEI formation on Si films. The measured mass uptake is split into a reversible part representing the battery function and an irreversible part attributed to continuous SEI formation. The evaluation of the latter quantifies the dependence of SEI growth on cycling window, rate and anode thickness. More striking is the reversible part. Advanced QCM mass spectrometry enables identification of the ab/desorbed species. Surprisingly, half of the battery storage is not due to lithiation but due to reversible adsorption of Li2O to the SEI layer. The dependence on rate and film thickness indicates this Li2O is formed by a self-limited, field-driven layer growth.

Towards a Hybrid Mass Sensing System by Combining a QCM Mass Sensor With a 3-DOF Mode Localized Coupled Resonator Stiffness Sensor

This paper describes a hybrid mass sensing system comprising a QCM (quartz crystal microbalance) mass sensor operating under atmospheric pressure and a 3-DOF mode localized coupled resonator operating in vacuum. Nanoparticles as consecutive mass perturbations are added onto the QCM, the output signals with respect to the amount of mass change are then being manipulated to generate electrostatic forces. Subsequently, the electrostatic forces act on the 3-DOF mode localized coupled resonator as external stiffness perturbations. The output metrics of the hybrid system were defined as: the resonant frequency shifts, vibration amplitude changes, and the changes in resonance amplitude ratio. Measured data was analyzed for these metrics and compared. This work demonstrated that the proposed hybrid mass sensing system attained a 2.5×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup> N(m · kg)-1 mass to stiffness transduction factor, and has the potential to be employed as a direct liquid contact biochemical transducer.

Uniformization of QCM’s Mass Sensitivity Distribution by Optimizing its Metal Electrode Configurations

The quartz crystal microbalance (QCM) is an ultra-sensitive measuring device and has been commonly used in many specific applications. The mass sensitivity distribution curve of m-m type QCM (QCM with symmetrical electrode) is a Gaussian distribution. However, achieving highly accurate and repeatable measurements requires the uniform distribution of mass sensitivity. To improve the uniformity of QCM mass sensitivity while ensuring high absolute mass sensitivity, the double-ring electrode geometry is designed. This study improves the size design of the double-ring electrode, and reveals the rules for varying sensitivity and electrode parameters based on a mathematical model. Through analyzing the mass sensitivity distribution of different electrode structures of QCMs, the uniformity of the double-ring electrode QCM is proved. The effects of mass sensitivity distribution of QCM are studied using the finite element method (FEM) by the variation of the size of electrodes, and an optimal size of electrode was discovered. Our results show that the double-ring type QCM has better uniformity of the mass sensitivity distribution and it can maintain the high mass sensitivity when the size of the inner ring of the double-ring electrode is close to half of the size of the outer ring. Meanwhile, there is an optimal outer radius that enables us to obtain an ideal and desirable displacement distribution. The numerical simulation results provide design ideas for the physical design of the double-ring type QCM.

Application of a quartz crystal microbalance to measure the mass concentration of combustion particle suspensions

Researchers studying the biological effects of combustion particles typically rely on suspending particles in de-ionized (DI) water, buffer, and/or media prior to in vitro or in vivo experiments. However, the hydrophobic nature of combustion particles makes it difficult to obtain well-suspended, evenly dispersed mixtures, which also makes it difficult to obtain equivalent dosing and endpoint comparisons. This study explored the use of a quartz crystal microbalance (QCM) to measure the mass concentration of combustion particle suspensions. It compared the QCM mass concentration to that estimated by placing a known mass of combustion particles in DI water. It also evaluated the effect of drop volume and combustion particle type on QCM measurements. The results showed that QCM is a promising direct method for measuring suspended combustion particle mass concentrations, and it is particularly effective for quantifying concentrations of difficult-to-suspend particles and for combustion particles placed in polystyrene containers, which can lead to substantial particle losses.

QCM Mass Sensitivity Analysis Based on Finite Element Method

The quartz crystal microbalance (QCM) mass sensitivity distribution based on a finite element method (FEM) is described in this paper. QCMs can measure the micromass through the measurement of resonance frequency; hence, it is widely applied in surface science, electrochemistry, biomedical science, and so on. It has the advantage of simple structure, label-free analysis, low price, and real-time output. However, the QCM measurement has a problem of lack of uniformity. After theoretical calculation and simulation, it was found that this deficiency is closely related to mass sensitivity. The QCM mass sensitivity depends on the metal electrode size, thickness, and shape. We calculated the QCM mass sensitivity based on Sauerbrey's equation, Bessel equation, and energy trapping. Then, the mass sensitivity was simulated based on FEM. The simulation result shows that the QCM mass sensitivity distribution is an approximate Gaussian curve. This method can help to better understand the mass sensitivity distribution, and give useful information to improve uniform of mass sensitivity distribution.

QCM mass underestimation in molecular biotechnology: Proximity ligation assay for norovirus detection as a case study

The development of piezoelectric mass-sensitive devices is based on the shift in resonance frequency that is proportional to the deposited mass. However, this holds true only for small, rigid masses, while it can result in mass underestimation for heavy, non-rigid masses. In this work, we demonstrate this ‘missing mass’ phenomenon by measurement of high molecular weight biomolecules on a Quartz Crystal Microbalance (QCM) platform. For this, we present a model bioassay consisting of a sandwich-type proximity ligation assay for the detection of norovirus-like particles, and its real-time build-up on QCM as an experimental evidence. Upon combination with a localized QCM platform, we explain the pronounced slipping effect in multilayer biological systems resulting in energy dissipation and subsequent mass underestimation. This helps in pointing out the limitations of mega-gravity field sensors for molecular diagnostics where absolute quantification of pathogen load becomes indispensable towards biosensing applications.

Research on the frequency stability of a bonded QCM for dew point measurement

A bonded structure of quartz crystal microbalance (QCM) based on finite element method to measure dew point is proposed. Adhesive joints of QCM have dominating impacts on QCM’s stability in a constant environment which is one of crucial problems in designing dew point sensors. Our main purpose is to seek an optimum bonding plan for keeping the frequency stability of dew point sensor. Considering that the QCM mass sensitivity distribution along the surface of the bonded QCM follows a Gaussian-type function, we use R-square as a standard to compare the frequency stability of the structure by changing material and dimension parameters of adhesive joints with the help of APDL language in ANSYS 15.0. At last, four QCMs bonding with various lengths of adhesive joints (L) are chosen for testing time and temperature drift, and the QCM with L less than 2 mm had better frequency stability revealed by partly simulation results.

Quartz crystal microbalance with microfluidic multi-stream solution control for mineralization kinetic analysis

We present a quartz crystal microbalance (QCM) sensor integrated with microfluidic multi-stream solution control for a variety of analysis applications, including improved studies of mineralization kinetics. The cost-effective assembly of this device and functionality of the QCM crystal in situations of rigid and viscoelastic mass loading are demonstrated. The significant advantage of this system is the control of solution mixing on-chip through the use of laminar parallel-flow which creates a liquid–liquid reaction interface at the QCM sensor. This shows improved sensor response times, due to laminar flow, of 105Hz/min compared to 19Hz/min for turbulent mixing in a bulk solution flow cell. This device adds to the current real-time mass measurements obtained from traditional QCM by allowing for simultaneous optical microscopy. The combination of QCM mass analysis, optical microscopy, and laminar parallel-flow to achieve a liquid–liquid reaction interface provides an analytical system well suited for the study of controlled mineralization. The microfluidic solution flow decreases non-specific mineralization and offers significant experimental control.

Pronounced aromatic carboxylic acid detection using a layer-by-layer mesoporous coating on optical fibre long period grating

In this work a new optical fibre sensor for the detection of aromatic carboxylic acids (ACAs) is proposed. The operation of the sensor is based on the measurement of the change in refractive index of a functional coating deposited onto the cladding of the optical fibre. Mesoporous thin films were fabricated using the layer-by-layer self-assembly of poly(allylamine hydrochloride) (PAH) and silica nanospheres (SiO 2 ) with a diameter in the range of 40–50 nm. The film was successfully deposited onto three different transducers; an optical fibre long-period grating (LPG), a quartz crystal microbalance (QCM) and a silicon wafer used in reflectometric interference spectroscopy (RIfS). The amino (NH 2 ) functional group of PAH was used as the binding site for the detection of ACAs. High sensitivity, with binding constants of 1.36 ± 0.01 × 10 6 and 5.6 ± 0.01 × 10 8 M −1 for benzoic acid and mellitic acid, respectively, was achieved. The lowest measured concentration of 1 nM of mellitic acid was achieved selectively over structurally (phenol) and functionally (acetic acid) related compounds. Concomitant refractive index (RI) and QCM mass changes were measured to validate the LPG response.

Importance of Trimethylaluminum Diffusion in Three-Step ABC Molecular Layer Deposition Using Trimethylaluminum, Ethanolamine, and Maleic Anhydride

Hybrid organic-inorganic films were grown by molecular layer deposition (MLD) with a three-step ABC reaction sequence using (A) trimethylaluminum (TMA), (B) ethanolamine (EA), and (C) maleic anhydride (MA) at 90 °C. Very large steady state mass gains of 1854-4220 ng/(cm(2) cycle) were measured depending on reaction conditions. These mass gains are much larger than typical mass gains for surface reactions. The quartz crystal microbalance (QCM) mass profiles during the TMA reaction were consistent with TMA diffusion into and out of the ABC films. The ABC mass gains per cycle also displayed a strong dependence on the TMA dose and purge times that was consistent with the effects of TMA diffusion. Multiple dose experiments conducted at 130 °C revealed that the ABC reactions were self-limiting for thin ABC films. For thicker ABC films, increased TMA diffusion into the ABC film led to non-self-limiting behavior. Numerical modeling assuming Fickian diffusion for TMA diffusing into and out of the ABC film could fit the QCM mass profiles. The results all indicate that TMA diffusion into the ABC MLD film plays a key role in the thin film growth. In addition, X-ray reflectivity (XRR) measurements revealed that the ABC films were exceptionally smooth.

Proximity Effect in Quartz Crystal Microbalance

When an object approaches a vibrating quartz crystal microbalance (QCM) the resonant frequency changes. This "proximity effect" was seen at the distance of 10 mm in air and became more pronounced as the distance decreased. This effect depends on the quality factor (Q-factor) value of a QCM, conductivity of the object, and electrical connection of the object to QCM electrodes. A special setup was constructed to test the impact of the proximity effect on a QCM. Damping fluid was placed on one side of QCM, to change the Q-factor. A conducting metal disk was brought close to the other side of the QCM exposed to air. By varying the distance between the QCM and an object (metal disk), a shift in frequency was observed. This proximity effect was largest (>200 Hz for 10 MHz QCM) when the Q-factor was low and a conducting metal disk (e.g., Cu) was electrically shorted to the proximal (nearest) QCM electrode. The finite element modeling showed that the proximity effect was likely due to interaction of the object with the fringing electromagnetic field of the QCM. A simple modified Butterworth Van-Dyke model was used to describe this effect. It must be recognized that this effect may lead to large experimental artifacts in a variety of analytical QCM applications where the Q-factor changes. Therefore, in order to avoid artifacts, QCM and similar mass acoustic devices should not operate in the low Q-factor (<1000) regime.

Quartz Crystal Microbalance Detection of Glutathione-Protected Nanoclusters Using Antibody Recognition

A quartz crystal microbalance (QCM) immunosensor was developed for the quantitative detection of glutathione-protected nanoclusters. Advantages intrinsic to QCM were employed to make it an attractive alternative to other immunosensing techniques. We have addressed challenges in the area of QCM mass sensing through experimental correlation between damping resistance and frequency change for a reliable mass measurement. Electrode functionalization was optimized with the use of protein A to immobilize and present polyclonal IgG for antigen binding. This method was developed for the detection of glutathione (antigen)-protected clusters of nanometer size with high surface area and thiolate valency. Quantitation of glutathione-nanocluster binding to immobilized polyclonal antibody provides equilibrium constants (K(a) = (3.6 +/- 0.2) x 10(5) M(-1)) and kinetic rate constants (k(f) = (5.4 +/- 0.7) x 10(1) M(-1) s(-1) and k(r) = (1.5 +/- 0.4) x10(-4) s(-1)) comparable to literature reports. These observations further imply that immunoreactive nanoparticles have potential in medical diagnostics and materials assembly.

Effect of the Polycation Nature on the Structure of Layer-by-Layer Electrostatically Self-Assembled Multilayers of Polyphenol Oxidase

Self-assembled multilayers comprised of alternate layers of polyphenol oxidase (PPO) and poly(allylamine) (PAH) or PPO and poly(diallyldimethylamine) (PDDA), deposited on a 3-mercaptopropanesulfonic acid (MPS)-modified gold surface, were studied "in-situ" (under water) by means of ellipsometry and quartz crystal microbalance (QCM), and "ex-situ" (in open air) by ellipsometry and fourier transform infrared reflection-absorption spectroscopy (FT-IRRAS). Optical ellipsometric properties of (PAH)(n)(PPO)(n) and (PDDA)(n)(PPO)(n) multilayers were obtained at two wavelengths, employing an isotropic single-layer model with the substrate parameters measured after thiol adsorption. Film thickness as well as ellipsometric mass values based on the de Feijter equation were also evaluated. The quartz crystal impedance analysis showed that self-assembled multilayers behaved as acoustically thin films, and therefore, the shifts observed in the film inductive impedance parameter were interpreted in terms of gravimetric mass. The enzyme mass up-take in each adsorption step was determined on PAH or on PDDA topmost layer. A comparative study between the ellipsometric thickness and acoustic mass values allowed us to obtain average values of "apparent" densities of (2.1 +/- 0.1) and (2.4 +/- 0.1) g cm(-3) for (PAH)(n)(PPO)(n) and (PDDA)(n)(PPO)(n) multilayers, respectively. The content of water included in the open polymer-enzyme structure was evaluated by comparison of QCM and ellipsometric mass values. FT-IRRAS spectra of each layer in (PAH)(n)(PPO)(n) and (PDDA)(n)(PPO)(n) films were recorded, and the intensity ratio of the amide bands was evaluated to obtain information about layer-by-layer enzyme conformation. An enzyme/polycation distribution model for (PAH)(n)(PPO)(n)and (PDDA)(n)(PPO)(n) multilayer structures is presented on the basis of combined ellipsometric, QCM, and FT-IRRAS results.

Direct monitoring kinetic studies of DNA polymerase reactions on a DNA-immobilized quartz-crystal microbalance.

Catalytic reactions of DNA polymerase I from E. coli (Klenow fragment, KF) were monitored directly with a template/primer (40/25- or 75/25-mer)-immobilized 27-MHz quartz-crystal microbalance (QCM). The 27-MHz QCM is a very sensitive mass-measuring device in aqueous solution, as the frequency decreases linearly with increasing mass on the QCM electrode at the nanogram level. Three steps in polymerase reactions which include 1) binding of DNA polymerase to the primer on the QCM (mass increase); 2) elongation of complementary nucleotides along the template (mass increase); and 3) release of the enzyme from the completely polymerized DNA (mass decrease), could be monitored continuously from the time dependencies of QCM frequency changes. The binding constant (Ka) of KF to the template/primer DNA was 10(8)M(-1) (k(on) = 10(5)M(-1)s(-1) and k(off)= 10(-3)s(-1)), and decreased to 10(6)M(-1) (k'on = 10(4)M(-1)s(-1) and k'off = 10(-2)s(-1)) for completely polymerized DNA. This is due to the 10-fold decrease in binding rate constant (k(on)) and 10-fold increase in dissociation rate constant (k(off)) for completed DNA strands. Ka values depended slightly on the template and primer sequences. The kinetic parameters in the elongation process (k(cat) and Km) depended only slightly on the DNA sequences. The repair process during the elongation catalyzed by KF could also be monitored in real time as QCM frequency changes.

Validation of antibody-based recognition by piezoelectric transducers through electroacoustic admittance analysis

The development of immunosensors based on piezoelectric transducers is widely investigated due to their attractive potentialities. The quartz crystal microbalance (QCM) may give a direct response signal which characterizes the binding event between a sensitive layer, immobilized onto the surface transducer, and the analyte to be detected. However, for small biomolecules, such as some antigens, it is quite difficult to obtain an observable signal. This is mainly due to the lack of sensitivity of the commonly used QCM (5 to 10 MHz quartz crystal). Moreover, the mass estimated with the QCM response through the Sauerbrey equation and the mass which can be measured thanks to other analytical techniques, in our case an enzymatic assay, are different: the deposited mass is generally overestimated by the QCM. To validate QCM mass measurements and, therefore antigens recognition, the interactions of acoustic shear waves with a biolayer were investigated during enzyme adsorption onto the microbalance gold electrode or during the antibody/antigen binding. Electroacoustic admittance was measured around the resonance frequency of a 27 MHz quartz resonator in parallel with microbalance measurements. The parameters which characterize the quartz microbalance equivalent circuit were compared with the classical microbalance frequency. The mass overestimation, given by the microbalance, could be explained either by modification of the rheological properties of the sensitive layers and/or by an inadequacy of the assay performed.

Total yield measurements in matrix‐assisted laser desorption using a quartz crystal microbalance

AbstractA quartz crystal microbalance (QCM) is employed to determine the desorption yield of neutral particles in matrix‐assisted laser desorption ionization. For ferulic acid, the matrix substance used, the QCM mass resolution of 1 ng corresponds to a detection limit of ≈︁1012 particles. Sample exposure effects are studied at different fluences by measuring the total desorption yield after consecutive laser pulses fired on the same spot on the sample. The dependence of the total yield on the fluence is studied for different angles of incidence of the laser beam. Varying the distance between the QCM and the sample yields information about the angular spread of the desorbed neutral particles. Additional information about the fluence threshold for the production of charged particles is gained by direct electronic measurements of sample charging.