Nanofluidic Chip Research Articles

Study on the condensate gas phase behavior in Nano-porous media

The pore size in shale has reached the nanoscale. The phase behavior of fluids in nanopores deviates from classical theory, making conventional phase theory inapplicable to shale reservoirs. It is thus of great significance to clarify the phase behavior at the nanometer pore scale in shale. Based on the shale reservoir in the Kaybob of the Duvernay shale, Canada, 6 nm and 10 nm cubic model systems were constructed, and a microscopic physical model was prepared included pathways at 10 nm, 40 nm, 500 nm, and micrometer scale. The fluid phase behavior in nanopores was studied using molecular simulations and nanofluidic chip experiments. The results show that during the retrograde condensation process, the condensate gas in small-scale pores condenses first and is less likely to evaporate as the pressure decreases. The conclusions drawn are: (1) In nanopores, the dew point pressure of condensate gas is higher than that of the bulk phase, and the smaller the scale of nanopores, the higher the dew point pressure. (2) The volume ratio of condensate in nanopores is higher, increasing as pore size decreases. (3) The condensation rate of condensate in nanoporous media varies slowly with pressure drop; During evaporation, the condensation rate of condensate in small pores varies more slowly with pressure drop compared to the bulk phase but is faster in large pores.

Nanofluidic Study of Multiscale Phase Transitions and Wax Precipitation in Shale Oil Reservoirs

During hydraulic fracturing of waxy shale oil reservoirs, the presence of fracturing fluid can influence the phase behavior of the fluid within the reservoir, and heat exchange between the fluids causes wax precipitation that impacts reservoir development. To investigate multiscale fluid phase transition and microscale flow impacted by fracturing fluid injection, this study conducted no-water phase behavior experiments, water injection wax precipitation experiments, and water-condition phase behavior experiments using a nanofluidic chip model. The results show that in the no-water phase experiment, the gasification occurred first in the large cracks, while the matrix throat was the last, and the bubble point pressure difference between the two was 12.1 MPa. The wax precipitation phenomena during fracturing fluid injection can be divided into granular wax in cracks, flake wax in cracks, and wax precipitation in the matrix throat, and the wax mainly accumulated in the microcracks and remained in the form of particles. Compared with the no-water conditions, the large cracks and matrix throat bubble point in the water conditions decreased by 6.1 MPa and 3.5 MPa, respectively, and the presence of the water phase reduced the material occupancy ratio at each pore scale. For the smallest matrix throat, the final gas occupancy ratio under the water conditions decreased from 32% to 24% in the experiment without water. This study provides valuable insight into reservoir fracture modification and guidance for the efficient development of similar reservoirs.

Nigella sativa, Anthemis hyaline and Citrus sinensis extracts reduce SARS-CoV-2 replication by fluctuating Rho GTPase, PI3K-AKT, and MAPK/ERK pathways in HeLa-CEACAM1a cells

Traditional remedies have long utilized Anthemis hyaline, Nigella sativa, and Citrus sinensis peel extracts as treatments for microbial infections. This study aimed to investigate the influence of Anthemis hyaline, Nigella sativa, and Citrus sinensis extracts on coronavirus replication and apoptosis-related pathways. HeLa-CEACAM1a cells were exposed to mouse hepatitis virus–A59. After viral inoculation, the mRNA levels of 36 genes were quantified using a Fluidigm Dynamic Array nanofluidic chip. IL-8 level and intracellular Ca2+ concentration was measured, and viral titer was assessed by the TCID50/ml assay to detect the extent of infection. Treatment with Nigella sativa extract surged the inflammatory cytokine IL-8 level at both 24 and 48-hour. Changes in gene expression were notable for RHOA, VAV3, ROCK2, CFL1, RASA1, and MPRIP genes following treatment with any of the extracts. The addition of Anthemis hyaline, Nigella sativa, or Citrus sinensis extracts to coronavirus-infected cells reduced viral presence, with Anthemis hyaline extract leading to a virtually undetectable viral load at 6- and 8-hours after infection. While all treatments influenced IL-8 production and viral levels, Anthemis hyaline extract displayed the most pronounced reduction in viral load. Consequently, Anthemis hyaline extract emerges as the most promising agent, harboring potential therapeutic compounds.

PH-Regulated Ionic Diode Based on an Asymmetric Shaped Multiple-Layer Polymer Membrane

Smart artificial ion channels with tunable properties have wide applications in many fields to achieve ion transport manipulation. Most reported artificial ions are constructed with vertical structures, limiting the further integration of ionic diodes into complex iontronic systems. Inspired by the asymmetric concentration polarization induced by the asymmetric geometry of nanochannels, a novel method is developed to construct horizontally arranged and pH-regulated ionic diodes in nanofluidic chips by self-assembling pH-responsive polymers. The effects of the fabrication and operation parameters on the performance of the ionic diode are systematically investigated. The current rectification ratio of the ionic diode can be modulated flexibly by regulating the pH conditions of the working fluid. An ionic diode bridge circuit for rectifying alternating current signals is built in a single nanofluidic chip and demonstrated, highlighting the feasibility of the ionic diode for complex iontronic system integration. The method presented in this paper provides a promising platform for the development of smart nanofluidic iontronic devices with widespread applicability in biological analysis, sensing, and logic computing.

Digital recombinase polymerase amplification in hydrogel nanofluidic chip for ultrafast and precise quantification of pathogens in fresh food

The fast and precise point-of-care quantification of pathogens is an effective way to monitor and control diseases. In this work, we report a digital recombinase polymerase amplification (dRPA) in hydrogel nanofluidic chip for absolute quantification of nucleic acids as short as 5 min, without the need for complex chip operation. To perform the hydrogel RPA (gRPA), the RPA mixture with hydrogel monomers was introduced into a chip for cross-linking, followed by 39 °C amplification, resulting in a series of dots for digital counting. Since traditional Poisson distribution theory was no longer applicable here, a novel “Random Overlapping Theory” was developed for the first time for gRPA to calibrate the precise number of nucleic acids. With simple operation, the developed gRPA avoids pre-amplification during sample loading and partition. The detection performance of the nanofluidic system was analyzed by testing Listeria monocytogenes, confirming excellent quantitative ability with the limit of detection down to a single copy. This method is also demonstrated to possess excellent performance in real complex fresh food. Due to the facile operation, short detection time, low cost and low temperature required, as well as excellent quantification ability, we believe that the developed method will play an important role in point-of-care tests, especially in resource-limited areas.

Review on Development System of Traceability in Dairy Processing

The application of molecular methods is widely implemented in the traceability systems in the food sector, covering many types of food, as it is shown in this review. The rapid implementation of traceability systems in the food system is due to these techniques with high specificity, sensitivity, efficiency, and speed. In addition, compared with protein-based techniques, DNA-based techniques can be applied to any type of product, regardless of the treatment of processing to which it has been subjected. Future trends in the development of molecular or genetic tools for food traceability are focused on the search of techniques to obtain more information in the shortest time possible. Techniques that allow the identification, both at the species and population level, also facilitate the determination of the geographic origin. At present, one of the most promising techniques is the Digital PCR (dPCR), which allows the analysis of samples containing mixtures of species with high sensitivity and in a single assay, making multiple reactions in parallel through a nanofluidic chip. The application of emerging technologies, microfluidics, and nanotechnology in the development of molecular methods will obtain greater sensitivity, discriminatory power, reproducibility, and speed, thus increasing its potential in the traceability of the food sector.

Nanofluidic chip on tube as standard leak elements

The nanofluidic chips with channels of 100-nm depth and 3-μm width were employed as molecular flow standard leak elements for vacuum technology applications in this paper. The nanofluidic chips are fabricated by MEMS technologies while the macro-micro connection is achieved using glass fusion bonding and standard Swagelok® Fitting. It is found that the choice of annealing temperature and holding time is a key issue regarding fusion bonding and the optimal processing parameters are 780 ℃, 5 min. Meanwhile, the sealing reliability of fusion bonding and the fitting connection is evaluated. Experiment shows that the flow conductance of the as-fabricated leak can reach 10−13 m3∙s−1 magnitude for He, N2 and Ar. This standard leak has the advantages of controlled dimensions, reliable connection, and constant flow conductance over a range of 105 Pa.

Temperature-regulated surface charge manipulates ionic current rectification in tapered nanofluidic channel

Diverse ionic current rectification methods for nanofluidic chips have recently emerged. Herein, we theoretically demonstrate that by applying a temperature gradient to the aqueous solution, the ionic rectification property of a tapered nanochannel can be manipulated by applying temperature gradients from the tip to base and vice versa. Our modeling results reveal that the rectification ratio can be significantly enhanced by applying a temperature increment from the base to tip, whereas the rectification ratio is significantly suppressed by applying a reverse temperature gradient. In addition to the solution temperature, we also investigated the influence of bulk ionic strength and tip height on the rectification ratio, thereby providing overlapping and non-overlapping regimes of electrical double layers. We demonstrate that the rectification behavior of a tapered nanochannel is determined by the overlapping regime of the electrical double layer at the tip of the nanochannel. Moreover, we propose a semi-analytical solution that can capture numerical results with the same order of magnitude. We expect that the modeling results of this contribution can provide a direction for understanding ionic transport across geometrically and thermally asymmetrical media, which could find applications from energy conversion to logical nanofluidic chip components.

Nanopore chip with self-aligned transverse tunneling junction for DNA detection

To achieve better signal quality and resolution in nanopore sequencing, there has been strong interest in quantum tunneling based detection which requires integration of tunneling junctions in nanopores. However, there has been very limited success due to precision and reproducibility issues. Here we report a new strategy based on feedback-controlled electrochemical processes in a confined nanoscale space to construct nanopore devices with self-aligned transverse tunneling junctions, all embedded on a nanofluidic chip. We demonstrate high-yield (>93%) correlated detection of translocating DNAs from both the ionic channel and the tunneling junction with enriched event rate. We also observed events attributed to non-translocating DNA making contact with the transverse electrodes. Existing challenges for precise sequencing are discussed, including fast translocation speed, and interference from transient electrostatic signals from fast-moving DNAs. Our work can serve as a first step to provide an accessible, and reproducible platform enabling further optimizations for tunneling-based DNA detection, and potentially sequencing.

Ionic Diode Based on an Asymmetric‐Shaped Carbon Black Nanoparticle Membrane

AbstractBioinspired ionic diodes are widely explored to mimic the controllable ion transport of biological ion channels. However, due to their vertical structures, the integration of conventional ionic diodes into complex ionic circuits is still a challenge. Here, a horizontal ionic diode is developed based on an asymmetric nanochannel network membrane (NCNM) constructed from carbon black nanoparticles. The rectification of ionic current is achieved through the asymmetric concentration polarization of ions at two ends of the asymmetric NCNM. The rectification ratio of the NCNM ionic diode can be modified flexibly by changing the working fluid and the geometry of the NCNM. It is found that with the presence of cationic surfactant in the working fluid, the rectification ratio increases more than 30 times from 3.03 to 109.77. Advanced functions of the developed ionic component, including working as an ionic transistor for current switching and integrating into an ionic diode bridge on a single nanofluidic chip for rectifying alternating current signals, are also demonstrated in this paper. The horizontally arranged NCNM ionic diode possesses the advantages of easy fabrication and integration that can be practically applied in the development of ionic electronics and biocomputing.

Novel Application of Nanofluidic Chip Digital PCR for Detection of African Swine Fever Virus.

African swine fever virus (ASFV) gives rise to a grievous transboundary and infectious disease, African swine fever (ASF), which has caused a great economic loss in the swine industry. To prevent and control ASF, once suspicious symptoms have presented, the movement of animal and pork products should be stopped, and then, laboratory testing should be adopted to diagnose ASF. A method for ASFV DNA quantification is presented in this research, which utilizes the next-generation PCR platform, nanofluidic chip digital PCR (cdPCR). The cdPCR detection showed good linearity and repeatability. The limit of detection for cdPCR is 30.1995 copies per reaction, whereas no non-specific amplification curve was found with other swine viruses. In the detection of 69 clinical samples, the cdPCR showed significant consistency [91.30% (63/69)] to the Office International des Epizooties-approved quantitative PCR. Compared with the commercial quantitative PCR kit, the sensitivity of the cdPCR assay was 86.27% (44/50), and the specificity was 94.44% (17/18). The positive coincidence rate of the cdPCR assay was 88% (44/50). The total coincidence rate of the cdPCR and kit was 89.86% (62/69), and the kappa value reached 0.800 (P < 0.0001). This is the first time that cdPCR has been applied to detecting ASFV successfully.

Profiling of Autophagy-Associated microRNAs in the Osteosarcoma Cell Line of U2OS.

Autophagy is a cellular process that plays a role in the destruction of proteins and organelles. It has been shown that impaired autophagic flux triggers canceration, infectious disease, and neurodegenerative diseases. It has been suggested that tumor formation is inhibited by autophagy that reduces oxidative stress and recycles damaged organelles. microRNAs are 17-25 bp in length, single-stranded, and noncoding small RNAs that play roles in the regulation of metabolic gene expression at the post-transcriptional level. Osteosarcoma is an aggressive bone cancer that affects mainly children and adolescents. The current article aims to profile autophagy-associated miRNAs in osteosarcoma cell lines and to examine the therapeutical potentials of these miRNAs by suppressing their expressions with Adriamycin and Rapamycin. We used fluidigm dynamic array nanofluidic chip 96.96 for mRNA expression assay in osteosarcoma cell line U2OS. It was probed that after the suppression of autophagy-associated miRNAs by adriamycin and rapamycin, while most of the miRNAs were down-regulated in osteosarcoma cell lines, some miRNAs' expressions, such as miR-3141, miR-4296, miR-133b, and miR-720, were strikingly increased. Rapamycin and adriamycin, mTOR inhibitors, stir autophagic machinery, which results in decreased cell survival. Together, we propose that the expressions of miR-3141, miR-4296, miR-133b, and miR-720 might exacerbate the pathogenesis of osteosarcoma; therefore, the suppression of these miRNAs with the loss-offunction approaches could be an appropriate strategy that is worth testing in osteosarcoma.

Nanofluidic Immobilization and Growth Detection of Escherichia coli in a Chip for Antibiotic Susceptibility Testing.

Infections with antimicrobial resistant bacteria are a rising threat for global healthcare as more and more antibiotics lose their effectiveness against bacterial pathogens. To guarantee the long-term effectiveness of broad-spectrum antibiotics, they may only be prescribed when inevitably required. In order to make a reliable assessment of which antibiotics are effective, rapid point-of-care tests are needed. This can be achieved with fast phenotypic microfluidic tests, which can cope with low bacterial concentrations and work label-free. Here, we present a novel optofluidic chip with a cross-flow immobilization principle using a regular array of nanogaps to concentrate bacteria and detect their growth label-free under the influence of antibiotics. The interferometric measuring principle enabled the detection of the growth of Escherichia coli in under 4 h with a sample volume of 187.2 µL and a doubling time of 79 min. In proof-of-concept experiments, we could show that the method can distinguish between bacterial growth and its inhibition by antibiotics. The results indicate that the nanofluidic chip approach provides a very promising concept for future rapid and label-free antimicrobial susceptibility tests.

Inside Back Cover: Biotechnology Journal 1/2020

The fully integrated Beacon cell culture system enables the manipulation, culturing and assaying of thousands of clones on a single nanofluidic chip. The Beacon platform allows for the generation of clonally derived cell lines of known phenotypic identity with a superior clonality data package, detailed tracking, rapid verification of clonal origin, and 99 % assurance of clonality. This is reported by Kim Le, Christopher Tan, Huong Le, Jasmine Tat, Ewelina Zasadzinska, Jonathan Diep, Ryan Zastrow, Chun Chen,and Jennitte Stevens in article 1900247.

Nanofluidic devices prepared by an atomic force microscopy-based single-scratch approach.

Nanofluidic chips with different numbers of nanochannels were fabricated based on a commercial AFM system using a single-scratch approach. The electrical characterization and enzymatic reactions at the nanoscale were demonstrated using the obtained chips. The effects of the number of nanochannels and the solution concentration on the measured electric current were investigated. The influence of the hydrodynamic convection generated from the induced inflow at the end of the nanochannel on the ion transport through the nanochannel was also studied. Moreover, the enzymatic reactions for trypsin towards poly-l-lysine (PLL) or thrombin were conducted with a nanofluidic chip to investigate the reaction specificity between trypsin and PLL. Results show that the electric current change during the experimental process could be used as a label-free indicator to detect the enzymatic activity.

A novel bonding method for fabrication of PMMA nanofluidic chip with low deformation of the nano-trenches

All PMMA-based nanofluidic chips are becoming increasingly important for biological and medical applications. To fabricate PMMA nanofluidic chips, the open nano-trenches should be sealed by thermal bonding method. However, the present thermal bonding method suffers from high deformation of nano-trenches due to PMMA softening near glass transition temperature. In this work, a novel bonding technique, based on acetone and ethanol (v:v, 8:2) treatment, is developed to adjust the Young’s modulus of PMMA in its surface layer. By optimizing nanoimprinting and bonding process, PMMA nanofluidic chip was fabricated without undesired nano-trench deformation. The integrity of the enclosed PMMA nanofluidic system was verified by a fluorescence filling experiment.

Nanofluidic fluorescence microscopy with integrated concentration gradient generation for one-shot parallel kinetic assays

We report a simple and cost-effective nanofluidic fluorescence microscopy platform with parallel kinetic assay capability for the determination of kinetic parameters in a single run. An on-chip microfluidic concentration diluter, or gradient generator, was integrated to a biofunctionalized nanofluidic chip, enabling simultaneous interrogation of multiple biomolecular interactions with a full titration series of analyte in a single experiment. We demonstrate that since the association and dissociation phases are induced by the on-chip gradient generator and a reverse buffer flow operation, complete kinetic sensorgrams for IgG/anti-IgG interactions can be achieved within 20 min on a single device, which is at least 10 times faster than traditional kinetic techniques. This method could contribute to low-cost, rapid and high-throughput drug-screening and clinical diagnostics.

Nano-electrokinetic ion concentration in the ion enrichment zone

To reveal the internal discipline and accurately identify the inflection point, the Poisson–Nernst–Planck equations combined with the Navier–Stokes equation are employed and a method based on the horizontal angle of the tangent line and the distance from a pointcut to the origin is presented. Utilizing a micromachining technique and a photopolymerization reaction, a polyacrylamide gel plug is integrated into a microchannel to form a micro–nanofluidic chip. With the chip, FITC concentration experiments are developed with the initial concentration of 10 nM. Experimental testing confirms the results and demonstrates that the concentration is increased at first and then decreased with the increasing of the electric potential. That variation trend should be attributed to a balance between the repulsive force and the electrophoresis effect. The research results also demonstrate that upon increasing the voltage, the horizontal angle first decreases and then increases corresponding with the reverse trend of the distance. For a given micro–nanochannel, the peak ion concentration can be obtained through decreasing the horizontal angle and increasing the distance. The results will help determine peak voltage.

Polycarbonate Nanofluidic Chip Fabrication Technique by Hot Embossing and Thermal Bonding.

Nanofluidic devices are becoming increasingly critical for medical, chemical and biological applications. In this paper, a 2D Polycarbonate (PC) nanofluidic chip was fabricated by hot embossing and thermal bonding method. In this paper, the effect of the hot embossing parameters on the replication precision of 2D PC nanochannels was investigated by finite element method. To increase the bonding rate of the chip, the parameters of the thermal bonding process were optimized. Under the optimized parameters the 2D PC nanofluidic chip was successfully fabricated. The results show that the replication precision of the nanochannels can be as high as 97% and the bonding rate of the chip can be 96%. The fluorescent images demonstrate that there is no block and leakage through the whole microchannels and nanochannels. It is expected that this fabrication method has great potential to fabricate 2D nanofluidic chip with low cost and high precision.

Flow patterns of oil–water two-phase flow during pressure-driven process in nanoscale fluidic chips

Unconventional oil reservoirs have great potential to become significant sources of petroleum production in the future. Many shale oil systems consist of nanoscale pores and fractures that are significantly smaller than those from conventional reservoirs, and pore sizes are only slightly more than one order of magnitude of those of the saturating fluid molecules. This difference will cause abnormal wettability effect and typical fluid flow mechanisms in unconventional oil systems. Therefore, it is increasingly important to investigate fluid flow behaviours in nanoscale porous media. In this work, a lab-on-chip approach for the direct visualization of the water–oil flow in nanoscale channels was developed by using an advanced laser microscopy system combined with a nanofluidic chip. For the micro-scale study of interface transmission during the drainage and imbibition processes, parallel linear nanofluidic chips were used. A comprehensive study of water–oil flow behaviours is presented. During the drainage process, liquids tend to have a piston-like flow in nanoscale channels; both residual phase saturation and configuration affect the flow behaviour on such small scale; during the imbibition process, a fading-out phenomenon was observed. For a macroscale study of pressure and recovery relationships, unusual entrance pressure was discovered by using network nanofluidic chips comparing to conventional results.