Despite numerous studies about Marangoni instabilities, there are very few of them conducted for the menisci in microscale channels or tubes. In this paper, the onset of Marangoni flow on an ...initially isothermal meniscus in a capillary channel is studied. The temperature gradient perpendicular to the meniscus is found arousing a BACOnardaMarangoni instability when the channel size or the temperature gradient beyond certain values. The threshold Marangoni Number for the instability is obtained, which turns out to be dependent on the Biot Number. The evolution of the meniscus flow patterns with increasing Marangoni Number is studied. The influences of gravity are discussed. The present work is a preliminary step to a comprehensive understanding of Marangoni instability in capillary structures. The temperature gradient that is perpendicular to the meniscus should be paid attention to in the related applications.
Partial filling of mixed ferrite (Ni0.5Zn0.5Fe2O4; NZFO) nanoparticles into the amorphous carbon nanotubes (aCNTs) cavity is achieved by simple mixing of the aqueous dispersions of the two (aCNTs and ...NZFO) at room temperature. The process of incorporation of the nanoparticles into the aCNT cavity is solely mediated by the capillary action of the liquid. NZFO nanoparticles were homogeneously dispersed in the aqueous solution but after mixing they are sparsely distributed into the aCNT channel as a result of the capillary action. The encapsulation of the nanoparticles into the aCNTs amorphous shield was established by means of X-ray diffraction, transmission electron microscopy, Fourier transformed infrared spectroscopy, and Raman spectroscopic analysis. Such entrapment of the nanoparticles causes the composite nanotubes superparamagnetic in nature with blocking temperature (T B) at 15 K. However, compared to the powder NZFO nanoparticles, T B appears more sharply and at relatively lower temperature. Low filling density and the spatial confinement of the nanoparticles lessen the inter-particle interactions and the polydispersity within the NZFO nanoparticles which are manifested in their altered magnetic behavior.
•I have revised the manuscript “Spectral methods for capillary surfaces described by bounded generating curves” and submit these changes for consideration for publication.•I have substantially ...replaces the code snippets with a flowchart and I have added clear and detailed summaries of the goals of each table, as indicated was desired by the referee.
We consider capillary surfaces that are constructed by bounded generating curves. This class of surfaces includes radially symmetric and lower dimensional fluid-fluid interfaces. We use the arc-length representation of the differential equations for these surfaces to allow for vertical points and inflection points along the generating curve. These considerations admit fluids in capillary tubes, sessile drops, and fluids in annular tubes as well as other examples.
We present a pseudo-spectral method for approximating solutions of the associated boundary value problems based on interpolation by Chebyshev polynomials. This method is observably more stable than the traditional shooting method and it is computationally lean and fast. The algorithm is also adaptive, but does not use the adaptive automation in Chebfun.
Realizing ultrathin water and generating an abundant water/air interface in the interconnected pores of photothermal materials is an effective way to boost the solar‐driven water evaporation rate, ...but still a great challenge. Herein, confinement capillarity (CC) of photothermal thin coating on porous sponge for significantly enhancing the solar‐driven water evaporation is proposed. The thin coating is composed of abundant agminated black/hydrophilic nanoparticles (BHNPs), and the channels among the BHNPs can generate strong capillarity for water transportation. Water can be spontaneously limited and transported among the agminated nanoparticles, rather than fill in the interconnected pores of the sponge. Thus, ultrathin water layer can be realized on the outer/inner surface of the sponge skeleton, without precisely controlling water supply. The thin water layer can not only expose as much evaporation area as possible by increasing the vapor escape channel, but also prevent solar energy to heat excess water. Thanks to the CC, the rate of solar steam generation can be greatly improved. Moreover, the photothermal material with CC can maintain its high evaporation rate during the whole day, and can remove the salt during night time, highlighting its recyclability and anti‐salt‐accumulation property. Moreover, the CC can be readily scaled up for practical applications.
Confinement capillarity (CC) can realize ultrathin water, generating an abundant water/air interface in the interconnected pores of photothermal materials. The resultant thin water layer can not only expose as much evaporation area as possible by increasing the vapor escape channel, but also prevent solar energy to heat excess water, significantly enhancing the solar‐driven water evaporation.
Wetting of low carbon steel by two industrial grades Al (4063 and 6061) alloys was investigated by the modified sessile drop method at temperatures between 600 and 750°C under high vacuum. The ...formation of intermetallics which would lead to the replacement of the oxidized surface by a clean surface, and further induces the spreading. The formation of precursor film in the wetting of Al 6061/steel was caused by subcutaneous infiltration mechanism. The different chemical compositions in Al alloys also lead to the different interfacial structures and spreading dynamics. The Mg in Al 6061 alloy reduces the oxide film and then make molten Al is easier to infiltrate into the steel substrate; the high affinity of the Si in Al 4043 alloy at Al/steel interface which induced the segregation of Si. The reduction reaction by the Mg in Al 6061 and the reaction between Al and Fe caused the apparent activation energy for spreading is almost an order of magnitude larger than Al 4043.
•Precursor film was observed in high reactive wetting system.•Wettability was improved by the volatile element (Mg) in Al alloys.•Typical characteristics of spreading dynamics in reactive wetting were observed.
Abstract
We present in the contribution an activity which is focused on wetting and capillarity. Experiments with hydrophobic coating are part of the activity too. We use this activity at lower and ...upper secondary school level, detailed description of the activity and our experience with it is discussed in the paper.
Small‐reactor‐based polymerase chain reaction (PCR) has attracted considerable attention. A significant number of tiny reactors must be prepared in parallel to capture, amplify, and accurately ...quantify few target genes in clinically relevant large volume, which, however, requires sophisticated microfabrication and longer sample‐to‐answer time. Here, single plasmonic cavity membrane is reported that not only enriches and captures few nucleic acids by taking advantage of both capillarity and hydrodynamic trapping but also quickly amplifies them for sensitive plasmonic detection. The plasmonic cavity membrane with few nanoliters in a void volume is fabricated by self‐assembling gold nanorods with SiO2 tips. Simulations reveal that hydrodynamic stagnation between the SiO2 tips is mainly responsible for the trapping of the nucleic acid in the membrane. Finally, it is shown that the plasmonic cavity membrane is capable of enriching severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) genes up to 20 000‐fold within 1 min, amplifying within 3 min, and detecting the trace genes as low as a single copy µL−1. It is anticipated that this work not only expands the utility of PCR but also provides an innovative way of the enrichment and detection of trace biomolecules in a variety of point‐of‐care testing applications.
Here, a plasmonic cavity membrane that is designed to not only enrich and capture trace nucleic acids in a clinically relevant large sample volume by taking advantage of capillarity and hydrodynamic trapping but also achieve rapid amplification and sensitive detection is reported.
Evaporation of sessile droplets containing non-volatile solutes dispersed in a volatile solvent leaves behind ring-like solid stains. As the volatile species evaporates, pinning of the contact line ...gives rise to capillary flows that transport non-volatile solutes to the contact line. This phenomenon, called the coffee-ring effect, compromises the overall performance of industrially relevant manufacturing processes involving evaporation such as printing, biochemical analysis, manufacturing of nano-structured materials through colloidal and macromolecular patterning. Various approaches have been developed to suppress this phenomenon, which is otherwise difficult to avoid. The coffee-ring effect has also been leveraged to prepare new materials through convection induced assembly. This review underlines not only the strategies developed to suppress the coffee-ring effect but also sheds light on approaches to arrive at novel processes and materials. Working principles and applicability of these strategies are discussed together with a critical comparison.
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•The coffee-ring effect compromises the overall performance of industrially relevant manufacturing processes involving drop evaporation.•The suppression of this unavoidable phenomenon is a challenge.•The coffee-ring effect has also been applied to improve biochemical analyses and processes.•This article reviews principles of various methods that suppress and utilize the coffee-ring effect.
We analyze a uniqueness result presented by Elcrat, Neel, and Siegel 1 for unbounded liquid bridges, and show that the proof they presented is incorrect. We add a hypothesis to their stated theorem ...and prove that their result holds under this condition. Then we use Chebyshev spectral methods to approximate solutions to certain boundary value problems used to check this hypothesis holds at least on a range of cases.
Liquid Metal Alloy Electrodes
A facile and versatile method is proposed to fabricate unlimited array of thick liquid metal alloy (LMA) electrodes, suitable for flexible electronics and functional ...materials etc. In article number 2310212, Liang Huang, Wenhui Wang, and co‐workers demonstrate LMA electrodes in microfluidics to bring the accumulative dielectrophoretic (DEP) deflection effect. 5000‐LMA‐electrode pairs show 10x higher throughput in DEP separation, and the throughput can be further improved by nearly 100x.
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