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.
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.
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.
The fluid-fluid interface is a complex environment for a floating object where the statics and dynamics may be governed by capillarity, gravity, inertia, and other external body forces. Yet, the ...alignment of these forces in intricate ways may result in beautiful pattern formation and self-assembly of these objects, as in the case of crystalline order observed with bubble rafts or colloidal particles. While interfacial self-assembly has been explored widely, controlled manipulation of floating objects,
e.g.
drops, at the fluid-fluid interface still remains a challenge largely unexplored. In this work, we reveal the self-assembly and manipulation of water drops floating at an oil-air interface. We show that the assembly occurs due to electrostatic interactions between the drops and their environment. We highlight the role of the boundary surrounding the system by showing that even drops with a net zero electric charge can self-assemble under certain conditions. Using experiments and theory, we show that the depth of the oil bath plays an important role in setting the distance between the self-assembled drops. Furthermore, we demonstrate ways to manipulate the drops actively and passively at the interface.
Water drops floating at an interface can be self-assembled and controlled using electrostatic effects. Uncharged drops can be moved around as desired, while charged drops exhibit spontaneous directed motion.
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