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Microfluidic approaches for the determination of interfacial tension and viscosity of liquid-liquid systems still face some challenges. One of them is liquid-liquid systems with low interfacial and high viscosity, because dripping flow in normal microdevices can’t be easily realized for the systems. In this work, we designed a capillary embedded step T-junction microdevice to develop a modified microfluidic approach to determine the interfacial tension of several systems, specially, for the systems with low interfacial tension and high viscosity. This method combines a classical T-junction geometry with a step to strengthen the shear force further to form monodispersed w/o or Aqueous Two-phase (ATP) droplet under dripping flow. For systems with low interfacial tension and high viscosity, the operating range for dripping flow is relative narrow whereas a wider dripping flow operating range can be realized in this step T-junction microdevice when the capillary number of the continuous phase is in the range of 0.01 to 0.7. Additionally, the viscosity of the continuous phase was also measured in the same microdevice. Several different systems with an interfacial tension from 1.0 to 8.0 mN·m−1 and a viscosity from 0.9 to 10 mPa·s were measured accurately. The experimental results are in good agreement with the data obtained from a commercial interfacial tensiometer and a spinning digital viscometer. This work could extend the application of microfluidic flows.

o-Nitrotoluene nitration can produce 2,4-dinitrotoluene and 2,6-dinitrotoluene simultaneously, which is also the common side-reaction of toluene mononitration. Kinetic study is helpful to deepen the understanding of nitration and control the reaction better. A homogeneously continuous microflow system was constructed to determine the kinetic parameters of 2-MNT nitration. A complete kinetic model was established and all kinetic parameters were obtained. In general, the observed reaction rate will increase with increasing H2SO4 mass fraction. However, when the H2SO4 mass fraction increases to a certain value, the observed reaction rate decreases. This is the first time to report the maximum observed reaction rate constant corresponding to the H2SO4 mass fraction at different temperatures in this work. Compared to previous reports on this reaction, the system provides more accurate kinetic parameters and can be developed into a reliable platform for the kinetic study of similar reactions.

A novel observation platform by placing the downstream observation window vertically has been constructed, and the actual micro-dispersion state can be exactly reflected in the observation window.

Tissues are highly complicated with spatial heterogeneity in gene expression. However, the cutting-edge single-cell RNA-seq technology eliminates the spatial information of individual cells, which contributes to the characterization of cell identities. Herein, we propose single-cell spatial position associated co-embeddings (scSpace), an integrative algorithm to distinguish spatially variable cell subclusters by reconstructing cells onto a pseudo-space with spatial transcriptome references (Visium, STARmap, Slide-seq, etc.). We demonstrated that scSpace can define biologically meaningful cell subpopulations neglected by single-cell RNA-seq or spatially resolved transcriptomics. The use of scSpace to uncover the spatial association within single-cell data, reproduced, the hierarchical distribution of cells in the brain cortex and liver lobules, and the regional variation of cells in heart ventricles and the intestinal villus. scSpace identified cell subclusters in intratelencephalic neurons, which were confirmed by their biomarkers. The application of scSpace in melanoma and Covid-19 exhibited a broad prospect in the discovery of spatial therapeutic markers.

Microfluidic technologies are reliable methods to obtain uniform and tiny droplets, but their application is limited by the capacity of single microchannel and the difficulty in fabrication and operation of large amounts of parallel droplet generators. Here, we reported a microchannel device equipped with multiple capillaries for rupturing the dispersed fluid, which realized droplet generation frequency up to 40 kHz in a single microchannel. The microchannel was operated under jetting flow, which was robust for controlling the droplet size uniformity; therefore, the device did not need highly precise machinery and accurate installation during fabrication. 30–100 μm droplets with CV

Doubled haploid breeding (DH breeding) is one of the major maize breeding techniques. The screening of haploid seeds is an essential link of DH breeding. Oil marking method is more stable than other haploid marking methods, which makes the oil content of haploid and diploid seeds significantly different. Currently, it is the most mature way to measure the oil content of maize seeds by nuclear magnetic resonance (NMR) spectrometer. However, the slow speed, high cost, and large volume have restricted the wide applications of NMR spectrometer. Similar to NMR, near infrared spectroscopy (NIRS) can also be used for the non-destructive screening of seeds. Moreover, compared with NMR spectrometer, NIRS spectrometer has a fast speed, low cost, and small volume. This study attempts to explore a maize haploid seed screening solution based on NIRS quantitative analysis to meet the demand of large-scale DH breeding. In this study, a screening solution for Maize Haploid seeds based on the quantitative analysis of NIRS is proposed, and tests of the solution by two representative varieties show a consistent average accuracy above 90%. A model monitoring and calibration solution based on small sample set is proposed to guarantee the stability and efficiency of the screening solution. The reason for the poor separability of the non-embryo side diffuse reflectance spectra is analyzed, and the feasibility of the non-embryo side spectra is verified by analyzing the spectral information of hyperspectral data. In summary, this research provides a more economical and efficient solution for maize haploid screening.

Liquid-liquid dispersion coupled with droplet formation and mass transfer of surfactants is one of the most typical phenomena in many chemical processes. As in every aspect of this process, the interfacial tension variation caused by the unsaturated adsorption of surfactants on the droplet surface plays an important role. This article focuses on microdroplet formation and the dynamic interfacial behavior of surfactants in the jetting regime. In a capillary embedded step T-junction device, controllable preparation of monodisperse droplets is achieved, and a correlation for predicting droplet sizes is established. A method for measuring the dynamic interfacial tension is provided. Mass transfer coefficients are then calculated for Tween 20 during the droplet formation process by a semiempirical correlation. The results indicate that dynamic interfacial tensions are lower than those obtained when the surfactant is adsorbed to equilibrium. Based on the tip-streaming phenomenon, mass transfer coefficients for Tween 20 can reach up to ∼10-3 m/s, higher than those obtained in coaxial microfluidic devices. All the preliminary results shed light on the nature of droplet formation and will be of significance for application in industrial apparatuses.

The kinetics of p-nitrotoluene nitration with mixed acid is important to industrial process design and safety control. However, it's difficult to acquire accurate kinetic data and no kinetics study has ever been reported before because of fast, highly exothermic and heterogeneous characteristics. In this work, a continuous-flow microreactor system including a micromixer, a capillary reactor and an online quenching module was designed to carry out the nitration under a homogeneous reaction condition. The homogeneous nitration can completely eliminate mass transfer resistance between phases, and accurately control reaction temperature and residence time in the continuous-flow microreactor system. The observed reaction rate constants separately based on HNO3 and NO2+, pre-exponential factor and activation energy of p-nitrotoluene nitration were obtained and a general method was established to collect kinetics data for such a kind of fast and highly exothermal nitration reactions.

The effects of varieties, producing areas, ears, and ear positions of maize on near-infrared (NIR) spectra were investigated to determine the factors causing the differences in NIR fingerprints of maize varieties. A total of 130 inbred lines were grown in two regions in China, and 12,350 kernel samples were analyzed through NIR spectroscopy. Spectral differences among varieties, producing areas, ears, and ear positions were determined and compared on the basis of pretreated spectra. The bands at 1300-1470, 1768-1949, 2010-2064, and 2235-2311 nm were mainly affected by the producing area. Band selection and principal component analysis were applied to improve the influence of variety on NIR spectra by processing the pretreated spectra. The degrees of the influence of varieties, producing areas, ears, and ear positions were calculated, and the percentages of the influence of varieties, producing areas, ears, and ear positions were 45.40%, 42.66%, 8.22%, and 3.72%, respectively. Therefore, genetic differences among maize inbred lines are the main factors accounted for NIR spectral differences. Producing area is a secondary factor. These results could provide a reference for researchers who authenticate varieties, perform geographical origin traceabilities, and conduct maize seed breeding.