Dynamic Quartz Crystal Microbalance Research Articles

Hydrodynamic slip in nanoconfined flows: a review of experimental, computational, and theoretical progress.

Nanofluidics has made significant impacts and advancements in various fields, including ultrafiltration, water desalination, biomedical applications, and energy conversion. These advancements are driven by the distinct behavior of fluids at the nanoscale, where the solid-fluid interaction characteristic lengthscale is in the same order of magnitude as the flow conduits. A key challenge in nanofluidics is understanding hydrodynamic slip, a phenomenon in which fluids flow past solid boundaries with a non-zero surface velocity, deviating from the classical no-slip boundary condition. This review consolidates experimental, computational, and theoretical efforts to elucidate the mechanisms behind hydrodynamic slip in nanoconfined flows. Key experimental methods, such as the surface force apparatus, atomic force microscopy, and micro-particle image velocimetry are evaluated alongside emerging techniques like suspended microchannel resonators, dynamic quartz crystal microbalance, and hybrid graphene/silica nanochannels, which have advanced hydrodynamic slip characterization at the nanoscale. In addition to direct slip measurement techniques, methods like sum frequency generation spectroscopy, X-ray reflectometry, and ellipsometry are discussed for their roles in probing solid-liquid interfacial interactions, shedding light on the origins of hydrodynamic slip. The review also highlights the contributions of molecular dynamics simulations, including both non-equilibrium (NEMD) and equilibrium (EMD) approaches, in modeling interfacial phenomena and slip behavior. Additionally, it explores the influence of factors such as surface wettability, shear rate, and confinement on slip, emphasizing the interaction between liquid structuring and solid-liquid interactions. Advancements made so far have uncovered more complexities in nanoconfined flows which have not been considered in the past, inviting more investigation to fully understand and control fluid behavior at the molecular level.

Microscopic Insight into Kinetics of Inorganic Scale Deposition during Smart Water Injection Using Dynamic Quartz Crystal Microbalance and Molecular Dynamics Simulation

Inorganic scale deposition has been found to affect many industrial processes, including water injection into the oil reservoirs. The incompatibility of high sulfate ion content of seawater with formation water containing calcium ion results in formation damage and production decline. In this study, several simultaneous techniques are utilized for qualitative and quantitative analysis of calcium sulfate scale to get more insight into the damage of formation during smart water flooding at micro and Nano scales. In the experimental section, calcium sulfate deposition due to the mixing of the formation water and seawater samples was investigated using the dynamic quartz crystal microbalance technique (DQCM). The effect of sulfate and magnesium ions existing in the seawater on the amount of calcium sulfate deposition were studied, individually. The results showed that the sulfate concentration of seawater could significantly change the mass deposition in a specific range. Also, at an optimal concentration of ...

Fibrinogen and albumin adsorption profiles on Ni-free Zr-based thin film metallic glass

In this study, we assessed the fibrinogen and albumin adsorption performance of Ni-free Zr-based (Zr53Cu33Al9Ta5) thin-film metallic glass (TFMG). Quartz crystal microbalance (QCM) system and fluorescence spectrophotometer were used to obtain protein adsorption measurements, using two different substrates (QCM and glass). Test samples were fabricated by coating both of the substrates with TFMG and Ti (widely used in implants) for comparison. In dynamic QCM as well as static fluorescence spectrophotometer tests, the TFMG achieved a lower fibrinogen to albumin adsorption ratio. The TFMG coating also exhibited high hydrophobicity (water contact angle of 96°) with low surface roughness of 1.06 nm and surface free energy of 35.3 mN/m. This is a clear demonstration of the excellent hemocompatibility of Ni-free Zr-based TFMG.

Kinetics and Control of Self-Assembly of ABH1 Hydrophobin from the Edible White Button Mushroom

Hydrophobins are small fungal proteins that self-assemble at hydrophobic/hydrophilic interfaces to form stable, amyloid membranes that are resistant to denaturation. Their remarkable surface activity has driven intense research for their potential utility in biomedical and cosmetic applications. In this research, the self-assembly characteristics of the Class I hydrophobin ABH1 from Agaricus bisporus , the edible white button mushroom, were evaluated as a function of solution and interface properties, in an attempt to gain greater mechanistic understanding. The kinetics of self-assembly were examined using dynamic quartz crystal microbalance techniques in combination with AFM, ellipsometry, contact angle goniometry, light scattering, and circular dichroism spectroscopy. It was found that the strength of interfacial tension between two phases drives the speed of ABH1 assembly and that the nature and location of the molecular ordering was influenced by temperature. ABH1 demonstrates different characteristics and self-assembly properties than those reported for other Class I hydrophobins, including causing an instantaneous decrease in surface tension in aqueous solution and undergoing a direct transition to β-sheet conformation on self-assembly at elevated temperature.

Quartz crystal microbalance monitoring of intervention of doxorubicin-loaded core–shell magnetic silica nanospheres on human breast cancer cells (MCF-7)

We prepare core–shell type magnetic silica nanospheres (Fe3O4@SiO2) as drug carriers for cellular delivery of the widely used anticancer drug doxorubicin (DOX). The cytotoxicity of doxorubicin-loaded magnetic silica composite (DOX-Fe3O4@SiO2) on human breast cancer cells (MCF-7) are studied by dynamic quartz crystal microbalance (QCM) monitoring, cyclic voltammetry (CV) characterization, 3-(4,5-dimethylthizaol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay and optical microscopic inspections, and agreeable conclusions are drawn from various methods. We find that the DOX-Fe3O4@SiO2 are able to induce cell death in a dose-dependent way and exhibit higher cytotoxicity under external magnetic field in comparison with the free DOX, suggesting the potential of the Fe3O4@SiO2 for targeting drug-delivery. The QCM sensor-based in situ/process monitoring in combination with ex situ/static analyses based on CV, MTT and optical microscopic inspections provides a reliable and informative experimental platform for investigating incubation of cells and interventions from exogenous substances.

Anti-electroviscous effect of near-surface 5CB liquid crystal and its boundary lubrication property

The rheological properties of the near-surface 5CB (4-pentyl-4′-cyanobiphenyl) liquid crystal (LC) under an external electric field (EEF) are investigated using a dynamic quartz crystal microbalance (QCM). The real-time film-forming process and shearing response of the EEF-induced absorbed LC liquid are studied. The results indicate that the EEF-induced adsorbed LC is composed of a bulk liquid layer and a near-surface boundary layer. Within the boundary layer, the nematic 5CB LC presents an anti-electroviscous effect which may be due to the EEF-induced ordered structure. According to the estimation from QCM measurements, this near-surface layer is about 100 nm thick under certain electric strength and is irreversible even after the EEF is removed. Based on a QCM model, the near-surface LC layer presents a decreased and irreversible viscosity as the EEF voltage increases against the reversible electro-viscous effect of the bulk 5CB liquid crystal measured by rheometer and Raman spectrum measurements. The anti-electroviscous effect of the near-surface 5CB layer is also proved by an improved boundary lubrication property tested on a tribometer. The coefficient of friction of 5CB LC after a preliminary induction of EEF is the lowest one compared to those without EEF and during the application of EEF. The unique anti-electroviscous property of near-surface 5CB LC revealed in this article suggests a potential method to actively reduce shear resistance in boundary lubrication and in microfluidics.

Combination of Electrografting and Atom-Transfer Radical Polymerization for Making the Stainless Steel Surface Antibacterial and Protein Antiadhesive

A two-step "grafting from" method has been successfully carried out, which is based on the electrografting of polyacrylate chains containing an initiator for the atom transfer radical polymerization (ATRP) of 2-(tert-butylamino)ethyl methacrylate (TBAEMA) or copolymerization of TBAEMA with either monomethyl ether of poly(ethylene oxide) methacrylate (PEOMA) or acrylic acid (AA) or styrene. The chemisorption of this type of polymer brushes onto stainless steel surfaces has potential in orthopaedic surgery. These films have been characterized by ATR-FTIR, Raman spectroscopy, atomic force microscopy (AFM), and measurement of contact angles of water. The polymer formed in solution by ATRP and that one detached on purpose from the surface have been analyzed by size exclusion chromathography (SEC) and (1)H NMR spectroscopy. The strong adherence of the films onto stainless steel has been assessed by peeling tests. AFM analysis has shown that addition of hydrophilic comonomers to the grafted chains decreases the surface roughness. According to dynamic quartz crystal microbalance experiments, proteins (e.g., fibrinogen) are more effectively repelled whenever copolymer brushes contain neutral hydrophilic (PEOMA) co-units rather than negatively charged groups (PAA salt). Moreover, a 2- to 3-fold decrease in the fibrinogen adsorption is observed when TBAEMA is copolymerized with either PEOMA or AA rather than homopolymerized or copolymerized with styrene. Compared to the bare stainless steel surface, brushes of polyTBAEMA, poly(TBAEMA-co-PEOMA) and poly(TBAEMA-co-AA) decrease the bacteria adhesion by 3 to 4 orders of magnitude as revealed by Gram-positive bacteria S. aureus adhesion tests.

Study on kinetics of early stage protein adsorption on poly(2-methoxyethylacrylate) (PMEA) surface

Abstract We have already reported that poly(2-methoxyethylacrylate) (PMEA) showed excellent blood compatibility featured by the significantly low adsorption of plasma protein and the low platelet adhesion. In this study, we tried to analyze the adsorption behavior of the plasma proteins (albumin and fibrinogen) on PMEA surface in terms of kinetics in the early stage of the adsorption reaction by using dynamic quartz crystal microbalance (QCM) method. In addition, the conformational changes of the proteins on the polymer surfaces were investigated. It was concluded from the results that the QCM method could be applied to the analysis of the kinetics in such a polymer–protein system. The characteristic of PMEA is that its detachment rate constant k−1, was higher than those from poly(2-hydroxyethylmethacrylate) (PHEMA) and polypropylene (PP) which were used as references. The degree of the conformational changes of the proteins decreases in the following order; PP>PHEMA>>PMEA. This was strongly related to the difference of the detachment rate constant k−1.

Electrochemical sensor for measurement of urea and creatinine in serum based on ac impedance measurement of enzyme-catalyzed polymer transformation.

Enzyme-catalyzed polymer transformation with electrochemical ac impedance detection has been employed for the measurement of urea and creatinine in serum samples. A polymer, based on poly(methylvinyl ether)/maleic anhydride modified by esterification with n-octanol, which is stable at pH 7.4 and which is transformed rapidly in response to alkaline pH changes, was linked to enzymatic reactions between urease and urea or creatinine deiminase and creatinine to produce a disposable sensor system. The polymer was screen-printed onto interdigitated screen-printed carbon electrodes and the electrodes overlaid with absorbent pads containing the relevant enzyme. Application of serum samples, "spiked" with either urea or creatinine, resulted in rapid polymer transformation, and resultant changes in the capacitance of the polymer-coated electrodes were analyte-concentration dependent. Additional information on the mechanisms of polymer transformation was obtained from dynamic quartz crystal microbalance measurements.

Improved Accuracy in Dynamic Quartz Crystal Microbalance Measurements of Surfactant Enhanced Spreading

Our previously reported quartz crystal microbalance (QCM) method for measuring dynamic wetting on solid substrates has been modified slightly to obtain more accurate spreading rates of aqueous dispersions of nonionic surfactants. Spreading rates are determined from analysis of frequency changes that occur as a result of an aqueous film containing dispersed surfactant spreading radially over the resonator surface following introduction of a small droplet to the center of QCM. The modification involves larger QCM electrodes, which increase the area over which the spreading event is measured compared to previously used smaller electrodes, and a frequency counter capable of more rapid data acquisition. The larger electrodes permit spreading to be measured over a larger area relative to the initial drop size and for longer time, while faster data acquisition provides more data immediately following introduction of the droplet to the QCM surface. This obviates overweighting of data acquired in the later stages of spreading when the aqueous film approaches the electrode edges and advances along the electrode tabs. These wetting rates were corroborated by real-time video microscopy of the wetting processes on identical surfaces. Comparison of the wetting rates on gold electrodes modified with various organosulfur monolayers reveals that the dependence of rates on surface energy is identical for the different electrode sizes, the rates being systematically larger for the larger electrodes.