Quartz Crystal Microbalance Surface Research Articles

Tuning friction and slip at solid-nanoparticle suspension interfaces by electric fields

We report an experimental Quartz Crystal Microbalance (QCM) study of tuning interfacial friction and slip lengths for aqueous suspensions of TiO2 and Al2O3 nanoparticles on planar platinum surfaces by external electric fields. Data were analyzed within theoretical frameworks that incorporate slippage at the QCM surface electrode or alternatively at the surface of adsorbed particles, yielding values for the slip lengths between 0 and 30 nm. Measurements were performed for negatively charged TiO2 and positively charged Al2O3 nanoparticles in both the absence and presence of external electric fields. Without the field the slip lengths inferred for the TiO2 suspensions were higher than those for the Al2O3 suspensions, a result that was consistent with contact angle measurements also performed on the samples. Attraction and retraction of particles perpendicular to the surface by means of an externally applied field resulted in increased and decreased interfacial friction levels and slip lengths. The variation was observed to be non-monotonic, with a profile attributed to the physical properties of interstitial water layers present between the nanoparticles and the platinum substrate.

Polystyrene Micro-pools Distribution on Quartz Crystal Microbalance (QCM) Surface using Ultrasonic Atomization Spray Coating

Surface morphology of polystyrene thin film is one of the significant factors to be take into account in the development of quartz crystal microbalance (QCM) as biosensor and chemical sensor. Many coating methods were developed to modify the morphology of polystyrene thin film surface. Our previous study showed that ultrasonic atomization spray coating (UASC) is a promised coating method to produce a rough polystyrene thin film on QCM sensor with patterns called micro-pools. There are many parameters that can affect the uniformity of micro-pools produced by UASC. In this work, 0.5% polystyrene solution which was solved in toluene was used as material coated onto a QCM sensor using UASC method. The effect of the distance variation between the spray nozzle and specimen towards the surface morphology of polystyrene thin film was observed. The surface morphology of the coated polystyrene and the micro-pools distribution were characterized by an optical microscope and Scanning Electron Microscope (SEM). The electrical impedance of the QCM was measured and characterized using Impedance Analyzer. The result showed that the optimum distance of the spray nozzle and specimen is between the range of 15 until 24 cm. At this optimum distance, the uniform micro-pools distribution was formed on the QCM surface without influencing the QCM acoustic impedance.

Improvement QCM Quality By Polystyrene Coating and Bovine Serum Albumin as Immobilization Agent

Polystyrene (PS) thin film with various concentration of mass (1%, 3%, and 5%) has been deposited onto Quartz Crystal Microbalance (QCM) surface by a spin coating method. The purpose of this research is the improvement of Bovine Serum Albumin (BSA) immobilization into the QCM surface. The QCM resonance frequency has been investigated by means of Impedance Analyzer. The film thickness was calculated by the Sauerbrey equation. The surface roughness of the PS layer was observed by noncontact Topography Measuring System (TMS-1200). Calculation result using a Sauerbrey equation shows the thickness of the PS layer increases with the increasing PS concentration. The QCM/PS with 1% and 5% concentration of mass has rougher morphology and more frequency shifts caused by BSA injection compared to 3% concentration of PS.

A fast-response and highly linear humidity sensor based on quartz crystal microbalance

A fast-response and highly linear humidity sensor based on quartz crystal microbalance (QCM) was prepared by using polyvinyl alcohol (PVA) and nano-silica composites as sensing film. The mass ratio of PVA to nano-silica and the total mass of sensing film which can significantly influence the response time and linearity of humidity sensor were well discussed. The results show that the optimal mass ratio of PVA to nano-silica is 1:1.5 and the total mass of the sensing film coated on the surface of QCM is 1.0 μg. Under the optimum conditions, the frequency shifts linearly respond to the relative humidity. The prepared humidity sensor has short response time (5 s), short recovery time (21 s), good stability and reproducibility. The developed humidity sensor is expected to be used for the detection of humidity in practice.

Specific responses of surface plasmon resonance and quartz crystal microbalance techniques to the mass of adsorbates at solid-liquid interfaces

Surface plasmon resonance (SPR) and quartz crystal microbalance (QCM) techniques are become increasingly popular in probing behaviors and properties of adsorbates at solid-liquid interfaces. Despite the numerous studies focusing on revealing various relations between their output signals and adsorbed mass, however, the mechanics of these specific relations remains elusive. In this paper, we showed that the universality of a proportional relation between SPR signal and surface mass stems from the catholicity of a linear relation between surface refractive index and surface concentration, and a small refractive index shift. The partial validity of a proportional relation between QCM signal and surface mass is due to that a linear relation between surface viscosity and surface concentration, and a small viscosity shift are not always true. The ratio of SPR and QCM signals to the surface mass is dominated by the refractive index increment and intrinsic viscosity, respectively. The weak sensitivity of refractive index increment to conformation, architecture, etc., makes the mass estimation from SPR technique very convenient. The strong sensitivity of intrinsic viscosity to these factors makes the mass evaluation from QCM technique very difficult, whereas endowing a powerful method in quantitatively probing the conformation of adsorbates at solid-liquid interfaces.

A preliminary study of identification halal gelatin using Quartz Crystal Microbalance (QCM) sensor

Gelatin has been widely used as an additive in pharmaceutical, cosmetic, and food industry. The similar physical appearance between bovine and porcine gelatin causes an issue for some communities like a Muslim due to awareness of halal food. A Muslim community consider porcine gelatin is non-halal material which must be avoided. So there is a demand to distinguish and labeling the origin source of the gelatin in any products. In turn, it lead to development of a method to identify the source of gelatin. In this study, performance of a modified Quartz Crystal Microbalance (QCM) sensor to identify halal gelatin has been investigated. A QCM sensor was modified by depositing polyaniline/nickel compound on the surface of gold electrode QCM carried out by Layer by Layer (LbL) deposition technique. Bovine and porcine gelatin were measured in demineralized water at pH 9. This modified QCM sensor shows good frequency response to distinguish bovine and porcine gelatin. The measurements gave a negative frequency shifts for bovine gelatin and a positive frequency shifts for porcine gelatin. The modified QCM sensor also worked well in the real sample. This indicates that a modified QCM sensor is very useful and effective technique to distinguish bovine gelatin (halal) from porcine gelatin (non-halal).

Real time evaluation of silicon epitaxial growth process by exhaust gas measurement using quartz crystal microbalance

A silicon epitaxial growth process in a trichlorosilane-hydrogen system was evaluated using a quartz crystal microbalance (QCM) placed at the exhaust of a chemical vapor deposition reactor designed for the Minimal Fab. The QCM showed two types of the frequency decrease behaviors, that is, i) a quick shift due to the gas property change caused by the trichlorosilane gas introduction into the ambient hydrogen and ii) the continuous and gradual decrease due to the byproduct deposition on the QCM surface during the silicon epitaxial growth. Because both i) and ii) showed a relationship with the silicon epitaxial growth rate, the in-situ information obtained by the QCM was expected for the real time monitoring of the film deposition process.

Cyclopropylamine plasma polymer surfaces for label-free SPR and QCM immunosensing of Salmonella

We report on the first successful application of nitrogen-containing functional surfaces prepared by plasma polymerization in surface plasmon resonance (SPR) immunosensing. The plasma polymers (PPs) were deposited from cyclopropylamine (CPA) vapors onto gold surfaces of SPR and quartz crystal microbalance (QCM) sensors. It provided an excellent platform for a stable immobilization of antibodies using glutaraldehyde (GA) activation. The performance of the SPR immunosensor was proven by a model pair of monoclonal antibody (Ab) AL-01 and human serum albumin as well as by the selective detection of bacterial pathogen Salmonella Typhimurium using the immobilized anti-Salmonella Ab. A baseline drift of the measured SPR signal, caused by the long-term reactivity of CPA plasma polymers, was well stabilized by 18 h immersion in phosphate buffered saline prior to the GA activation. The immunosensors can be successfully regenerated several times using 10 mM NaOH. The limit of detection of 105 CFU/mL and a wide linear response were achieved for Salmonella. The assay parameters are comparable to the conventional label-free methods. However, the replacement of conventional immobilization matrix with the CPA PPs offers an advantage of excellent adhesion to gold QCM and SPR surfaces achieved by fast and eco-friendly procedure compatible with the vacuum deposition of gold.

Adjustment and Measurement of Contact Angle with Electrowetting on a Quartz-Crystal Microbalance

Electrowetting-on-dielectric (EWOD) has been widely exploited as an actuating force to manipulate liquids by surface tension and modulation of the contact angle on a microscale. To evaluate EWOD, an optical measurement of the droplet contact angle is conventional, but is constrained by the optical properties of the liquid, especially when two liquid phases (e.g., water in oil) are involved. We developed a non-optical method to study EWOD using a quartz-crystal microbalance (QCM). A QCM provides a promising technique for mass sensing, and has been developed for the study of liquid viscosity, density and contact angle. In this research, a QCM was employed to generate EWOD and concurrently to measure the variation of the contact angle. The contact angle of droplets of water in air and in oil was evaluated. The voltage-dependent oil film between a water droplet and the QCM surface was sensed. A modified QCM model considering a voltage-dependent oil film was derived for the analysis of the contact angle.

Modified surface by poly(ethylene glycol) with looped conformation and its superior anticoagulant property

Poly(ethylene glycol) (PEG) is currently the gold standard for anticoagulant coatings. Up to now, most researchers focused on the impact of chain length and grafting density of PEG on protein adsorption, but few concerned about the effect of PEG conformation. Gold surfaces of quartz crystal microbalance with dissipation (QCM-D) with looped (SH-PEG-SH) and linear (SH-PEG) PEGs with different molecular weights ( M W=1000 and M W=5000) are prepared. Subsequently, fibrinogen adsorption and anticoagulant properties are measured as well. The compositions and phase structures of PEG modified surfaces are characterized by XPS and AFM. Compared with linear PEG surface, we find that looped PEG surface more efficiently prohibits fibrinogen adsorption, and then has superior antiplatelet and anti-erythrocytes adhesions properties. Fibrinogen adsorption results suggest that when the molecular weight of PEG is low ( M W=1000), the main reason for the fibrinogen resistance of looped PEG is the large surface coverage; when the molecular weight of PEG is high ( M W=5000), the fibrinogen resistance mechanism of looped PEG is a combination of the high viscoelasticity and the large surface coverage. This article provides valuable evidence and guidance for anticoagulant coating and application of high-performance biomaterials.

Controlled Deposition Number of Organic Molecules Using Quartz Crystal Microbalance Evaluated by Scanning Tunneling Microscopy Single-Molecule-Counting.

Precise control of organic molecule deposition on a substrate is quite important for fabricating single-molecule-based devices. In this study, we demonstrate whether a quartz-crystal microbalance (QCM) widely used for a film growth calibration has the ability to precisely measure the number of organic molecules adsorbed on a substrate. The well-known Sauerbrey's equation is extended to formulate the relation between QCM resonant frequency shift and the number of adsorbed molecules onto the QCM surface. The formula is examined by QCM measurements of sublimation of π-conjugated organic molecules and direct counting of the deposited molecules one by one onto metal substrates, using ultrahigh vacuum low-temperature scanning tunneling microscopy (STM). It is revealed that the number of adsorbed molecules evaluated by QCM ( NQCM) show good agreement with those counted from the STM images ( NSTM) within the error of ±25%. The results ensure the QCM capability for controlling the deposition number of organic molecules with high accuracy, that is, if one needs to deposit 100 molecules on the substrate, QCM control promises deposition of 100 ± 25 molecules.

Molecularly imprinted polymer based quartz crystal microbalance sensor system for sensitive and label-free detection of synthetic cannabinoids in urine

Herein, we prepared a novel quartz crystal microbalance (QCM) sensor for synthetic cannabinoids (JWH-073, JWH-073 butanoic acid, JWH-018 and JWH-018 pentanoic acid,) detection. Firstly, the synthetic cannabinoid (SCs) imprinted (MIP) and non-imprinted (NIP) nanoparticles were synthesized by mini-emulsion polymerization system. The SCs-imprinted nanoparticles were first characterized by SEM, TEM, zeta-size and FTIR-ATR analysis and then were dropped onto the gold QCM surface. The SCs-imprinted QCM sensor was characterized by an ellipsometer, contact angle, and AFM. The limit of detection was found as 0.3, 0.45, 0.4, 0.2 pg/mL JWH-018, JWH-073, JWH-018 pentanoic acid and JWH-073 butanoic acid, respectively. The selectivity of the SCs-imprinted QCM sensor was shown by using JWH-018, JWH-018 pentanoic acid, JWH-073 and JWH-073 butanoic acid. According to the results, the SCs-imprinted QCM sensors show highly selective and sensitive in a broad range of synthetic cannabinoid concentrations (0.0005–1.0 ng/mL) in both aqueous and synthetic urine solutions.

Superhydrophobic Polymerized n-Octadecylsilane Surface for BTEX Sensing and Stable Toluene/Water Selective Detection Based on QCM Sensor.

The present study reports a facile and low-cost route to produce a superhydrophobic polymerized n-octadecylsilane surface with micronano hierarchical structure on the surface of quartz crystal microbalance (QCM). The surface is used as a novel functional sensing material to detect benzene, toluene, ethylbenzene, and xylene (BTEX) vapor on the basis of QCM platform. The composites were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, and contact angle measurements. The type of solvent used to dissolve N-octadecyltrichlorosilane has a big impact on the morphology, wettability, and sensing performance of the polymer material. Further systematic studies suggest that surface wettability (contact angle) and molecular polarity of the detected analytes are effective factors in selective detection toward BTEX using resonator-type gas sensors. Gas sensing results toward toluene in different relative humidities show that the new-style sensor has stable toluene/water selective detection performance and that the disturbance of water is negligible. Besides, the limit of detection toward toluene of the sensor is lower than the odor threshold value.

Surface Modification Enhanced Reflection Intensity of Quartz Crystal Microbalance Sensors upon Molecular Adsorption.

Molecular adsorption on a sensing surface involves molecule-substrate and molecule-molecule interactions. Combining optical systems and a quartz crystal microbalance (QCM) on the same sensing surface allows the quantification of such interactions and reveals the physicochemical properties of the adsorbed molecules. However, low sensitivity of the current reflection-based techniques compared to the QCM technique hinders the quantitative analysis of the adsorption events. Here, a layer-by-layer surface modification of a QCM sensor is studied to increase the optical sensitivity. The intermediate layers of organic-inorganic molecules and metal-metal oxide were explored on a gold (Au) surface of a QCM sensor. First, polyhedral oligomeric silsesquioxane-derivatives that served as the organic-inorganic intermediate layer were synthesized and modified on the Au-QCM surface. Meanwhile, titanium oxide, fabricated by anodic oxidation of titanium, was used as a metal-metal oxide intermediate layer on a titanium-coated QCM surface. The developed technique enabled interrogation of the molecular adsorption owing to the enhanced optical sensitivity.

Understanding Interactions between Clay and Model Coal Surfaces in Electrolyte Solutions by a Quartz Crystal Microbalance with Dissipation Study

Clay slime coating is known to have a negative impact on coal flotation. It is therefore of great importance to study interactions between clay and coal under flotation conditions. In this study, the effect of electrolytes on the interactions of montmorillonite (MMT) clays with carbon or asphaltenes on sensor surfaces of quartz crystal microbalance with dissipation (QCM-D) as model coal was investigated. Ion beam sputtering deposition and spin coating methods were used to prepare carbon and asphaltene (a class of natural polyaromatic compounds) surfaces. The prepared surfaces were characterized by Raman spectroscopy. QCM-D was used to determine in situ interactions between MMT clays and model coal surfaces in electrolyte aqueous solutions. The MMT clays were shown to deposit significantly on the model coal surfaces only in the presence of NaCl or CaCl2 as a result of the compression of electrical double layers. Moreover the enhanced deposition by calcium ions is stronger than by sodium ions. The results f...

Preparation and ion sensing property of the self-assembled microgels by QCM

AbstractThe polyanion polystyrene sulfonate (PSS), the polycation poly (allylamine hydrochloride) (PAH), and the anionic poly (N-isopropylacrylamide-co-acrylic acid) [P(NIPAM-co-AA)] microgels were self-assembled onto the polyethylene imine (PEI) adsorbed gold surfaces of quartz crystal microbalance (QCM) because of the electrostatic attractions. The interactions of various metal particles including Ca2+, Bi3+, Cu2+, Zn2+, Ni2+, Sn2+, Co2+, and Cd2+with the obtained PEI/PSS/PAH/microgel layer in aqueous solutions were evaluated by QCM. The PEI/PSS/PAH/Microgel covered QCM sensor demonstrates the lowest detection limit of 0.1 ppm in aqueous solutions and the obviously linear connection between the frequency response and Ni2+concentration from 0.1 to 20 ppm, which is due to the complexation of Ni2+with the carboxyl groups of microgels. Atomic force microscopy (AFM) was used to reveal the morphology and stability of the self-assembled polyelectrolyte/microgel layer before and after adsorbing heavy metal ions. These self-assembled materials of polyelectrolyte/microgel layer will be helpful for manufacturing ion-selective materials for separation and identification purposes.

A Quartz Crystal Microbalance Immunosensor for Stem Cell Selection and Extraction.

A cost-effective immunosensor for the detection and isolation of dental pulp stem cells (DPSCs) based on a quartz crystal microbalance (QCM) has been developed. The recognition mechanism relies on anti-CD34 antibodies, DPSC-specific monoclonal antibodies that are anchored on the surface of the quartz crystals. Due to its high specificity, real time detection, and low cost, the proposed technology has a promising potential in the field of cell biology, for the simultaneous detection and sorting of stem cells from heterogeneous cell samples. The QCM surface was properly tailored through a biotinylated self-assembled monolayer (SAM). The biotin–avidin interaction was used to immobilize the biotinylated anti-CD34 antibody on the gold-coated quartz crystal. After antibody immobilization, a cellular pellet, with a mixed cell population, was analyzed; the results indicated that the developed QCM immunosensor is highly specific, being able to detect and sort only CD34+ cells. Our study suggests that the proposed technology can detect and efficiently sort any kind of cell from samples with high complexity, being simple, selective, and providing for more convenient and time-saving operations.

Piezoelectric biosensor for the determination of Tumor Necrosis Factor Alpha

Tumor Necrosis Factor Alpha (TNFα) is an important marker of inflammatory processes in human body. In the current healthcare, determination of TNFα blood or plasma level is done by Enzyme Linked Immuno-Sorbent Assay (ELISA) as a primary choice method. Piezoelectric immunosensors are analytical platform recording affinity interactions on their surface. It is inferred that the immunosensors would be a functional alternative to the ELISA. In this study, antibody against TNFα was immobilized on Quartz Crystal Microbalance (QCM) sensor and the same was made on magnetic particles. Human TNFα was measured in a way of interaction with QCM surface and then the particles were applied. The assay exerted sufficient limit of detection equal to 1.62pg/ml and it also fully correlated with standard ELISA tests. No interference by interleukin 6 or albumin was observed. Long term stability of the immunosensors lasting for at least three months was found. The immunosensors appears to be readily for practical performance and it would be an alternative to the standard ELISA especially when diagnoses made in field, homecare conditions or conditions of small hospitals as an emergency test.

Quartz crystal microbalance as an assay to detect anti-drug antibodies for the immunogenicity assessment of therapeutic biologics.

Because of their biological origins, therapeutic biologics can trigger an unwanted deleterious immune response with some patients. The immunogenicity of therapeutic biologics can affect drug efficacy and patient safety by the production of circulating anti-drug antibodies (ADA). In this study, quartz crystal microbalance (QCM) was developed as an assay to detect ADA. Etanercept (Enbrel®) was covalently grafted to dextran-modified QCM surfaces. Rabbits were immunized with etanercept to generate ADA. Results showed the QCM assay could detect purified ADA from rabbits at concentrations as low as 50ng/mL, within the sensitivity range of ELISA. The QCM assay could also assess the ADA isotype. It was shown that the ADA were composed of the IgG isotype, but not IgM, as expected. Furthermore, it was shown that QCM surfaces that had been used to detect ADA could be regenerated in glycine-HCl solution and reused. The QCM assay was also demonstrated to detect ADA in crude serum samples. Serum was collected from the rabbits and analyzed before and after etanercept immunization. ADA were clearly detected in serum from rabbits after immunization, but not in serum before immunization. Serum from patients administered with etanercept for rheumatoid arthritis (RA) treatment was also analyzed and compared to serum from healthy donors. Sera from 10 RA patients were analyzed. Results showed one of the RA patient serum samples may have ADA present. In conclusion, QCM appears to be a viable assay to detect ADA for the immunogenicity assessment of therapeutic biologics.

QCM Coupled Resonating Systems Under Vacuum: Sensitivity and Characteristics

We present the underlying physics in the resonance frequency characteristics of a bare quartz crystal microbalance (QCM) and a QCM-micro pillar based coupled resonator sensor (QCM-CRS) when they were subjected to pressure changes in a vacuum chamber. The QCMs experienced an increase in resonance frequency with decrease in pressure due to an inverse mass loading effect introduced on the QCM surface. However, when the pressure (below atmospheric pressure) dominated the mass loading, the resonance frequency of QCMs decreased. A sensitivity increase of 11 times to the pressure changes was observed for the case of QCM-CRS made of resonating micropillars attached around the central region of the electrode. In addition, the resonance frequency shift was linear for pressure changes between 31 and 71 kPa, demonstrating the possibility of employing the QCM-CRS as a vacuum detector element. The proposed sensor element is envisioned to have wide industrial applications ranging from detecting vacuum in chambers used in coating systems to crack detection in closed chambers.