We show that dielectric colloidal dimers with broken symmetry in geometry, composition, or interfacial charges can all propel in directions that are perpendicular to the applied ac electric field. The asymmetry in particle properties ultimately results in an unbalanced electrohydrodynamic flow on two sides of the particles. Consistent with scaling laws, the propulsion direction, speed, and orientation of dimers can be conveniently tuned by frequency. The new propulsion mechanism revealed here is important for building colloidal motors and studying collective behavior of active matter.

Electrochromatography is utilized to separate a mixture of 16 different polycyclic aromatic hydrocarbons (PAHs). Fused-silica capillary columns ranging in size from 50 to 150 µ i.d. were packed (20-40-cm sections) with 3•µ octadecylsilica particles. A potential of 15-30 kV is applied across the 30-50-cm total length capillary column to generate electroosmotic flow that carries the PAHs through the stationary phase. An intracavity-doubled argon ion laser operating at 257 nm is used to detect the PAHs by laser-induced fluorescence. Efficiencies up to

Full exploitation and utilization of the unconventional reservoirs of shale gas have become a central issue due to the increasing worldwide energy demand. Enhancing shale gas recovery by injecting CO2 is a promising technique that combines shale gas extraction and CO2 capture and storage (CCS) perfectly. In this study, a kerogen-based slit-shaped pore with a width of ∼21 Å was constructed by two kerogen matrices, and the grand canonical Monte Carlo (GCMC) and molecular dynamics (MD) simulation methods were used to investigate the adsorption and diffusion properties of CH4 and CO2 in the kerogen matrix and slit nanopores and explore the displacement efficiency of the residual CH4 by CO2 in kerogen slit nanopores. The adsorption energy of CH4 and CO2 on the kerogen fragment surface and the isosteric heat of CH4 and CO2 in kerogen slit nanopores were examined to demonstrate the competitive adsorption of CO2 over CH4 in kerogen slit nanopores, and the different intensity of interactions between the CH4 and CO2 molecules with the pore surface plays a key role. An effective displacement process of the residual adsorbed CH4 by CO2 in kerogen slit nanopores was performed. The efficiency of displacement was enhanced with the increasing bulk pressure, and the sequestration amount of CO2 in kerogen slit nanopores increased at the same time. Moreover, it was found that part of CH4 adsorbed firmly inside the intrinsic pores of the kerogenmatrix was very hard to be displaced by the CO2 injection. This work demonstrates the microbehaviors of CH4 and CO2 in kerogen slit nanopores and the microscopic mechanism of the displacement of CH4 by CO2, for the purpose of providing useful guidance for enhancing shale gas extraction by injecting CO2.

Recently, CRISPR-Cas technology has opened a new era of nucleic acid-based molecular diagnostics. However, current CRISPR-Cas-based nucleic acid biosensing has a lack of the quantitative detection ability and typically requires separate manual operations. Herein, we reported a dynamic aqueous multiphase reaction (DAMR) system for simple, sensitive and quantitative onepot CRISPR-Cas12a based molecular diagnosis by taking advantage of density difference of sucrose concentration. In the DAMR system, recombinase polymerase amplification (RPA) and CRISPR-Cas12a derived fluorescent detection occurred in spatially separated but connected aqueous phases. Our DAMR system was utilized to quantitatively detect human papillomavirus (HPV) 16 and 18 DNAs with sensitivities of 10 and 100 copies within less than 1 h. Multiplex detection of HPV16/18 in clinical human swab samples were successfully achieved in the DAMR system using 3D-printed microfluidic device. Furthermore, we demonstrated that target DNA in real human plasma samples can be directly amplified and detected in the DAMR system without complicated sample pretreatment. As demonstrated, the DAMR system has shown great potential for development of next-generation point-of-care molecular diagnostics.

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The effect of induced electro-osmosis on a cylindrical particle positioned next to a planar surface (wall) is studied theoretically both under the thin double layer approximation utilizing the Smoluchowski slip velocity approximation and under thick electric double layer conditions by solving the Poisson-Nernst-Planck (PNP) equations. The imposed, undisturbed electric field is parallel to the planar surface. The induced hydrodynamic and electrostatic forces are calculated as functions of the particle's and the medium's dielectric constants and the distance between the particle and the surface. The resultant force acting on the particle is directed normal to and away from the wall. The presence of such a repulsive force may adversely affect the interactions between macromolecules suspended in solution and wall-immobilized molecules and may be significant to near-wall particle imaging velocimetry (PIV) in electrokinetic flows.

Recently, bulk nanobubbles have attracted intensive attention due to the unique physicochemical properties and important potential applications in various fields. In this study, periodic pressure change was introduced to generate bulk nanobubbles. N2 nanobubbles with bimodal distribution and excellent stabilization were fabricated in nitrogen-saturated water solution. O2 and CO2 nanobubbles have also been created using this method and both have good stability. The influence of the action time of periodic pressure change on the generated N2 nanobubbles size was studied. It was interestingly found that, the size of the formed nanobubbles decreases with the increase of action time under constant frequency, which could be explained by the difference in the shrinkage and growth rate under different pressure conditions, thereby size-adjustable nanobubbles can be formed by regulating operating time. This study might provide valuable methodology for further investigations about properties and performances of bulk nanobubbles.

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