![]() ![]() 42,43 Even though the liquid–particle and interparticle forces dictate these outcomes, a generalized framework for analyzing liquid marbles based on these interactions is lacking. In practice, when the liquid is withdrawn from a liquid marble, drastically varying scenarios may occur including the physical distortion of liquid marbles such as buckling and crumpling, 8,40,41 particle multilayering, 8,33 or even the ejection of some particles from the liquid marble into the air. If an external stimulus, e.g., mechanical collision 9 or liquid withdrawal via evaporation, 8 stresses the liquid marble, additional forces may appear. Particles at the bottom also experience the weight of the drop (hydrostatics), which pushes them inside the liquid. Particles constituting the shell of a stationary spherical liquid marble experience coupled forces owing to weight ( F w), buoyancy ( F b), liquid–particle adhesion ( F adh), capillarity that exerts a compression force ( F c) on the particles, and interparticle friction ( F fr) that depends on F c and interparticle friction coefficient. Analytical approaches for modeling the evaporation of sessile liquid marbles 8,33 exploit empirical parameters that may not provide physical insights into the role of liquid–particle interfacial tension, particle surface roughness, 34 particle–particle friction coefficient, 35 and other attributes such as interfacial electrification. Despite the considerable interest and value of the above research, a unified framework for describing the mechanics of stressed liquid marbles, especially as they deflate, is unavailable. 2,27–32 Majority of these fundamental and applied studies evaluate liquid marbles thermo/electro/mechano/magneto-statically. 3 Several potential applications of liquid marbles have also been explored, such as for detecting water pollution, 11 monitoring environmental gases 12 and interfacial reactions, 13 bioreactors for blood typing, 14 cell culturing and screening, 15–18 polymerase chain reaction assay, 19 electrochemistry, 20 micellar self-assembly, 14,15,17,19,21,22 and magnetic translocation 23–26 among others. 1 Subsequently, many reports on the fundamental characteristics of liquid marbles have appeared, such as on their evaporation, 8 coalescence, 9 physical partitioning, 3 viscous dissipation during rolling, 1,10 and exposure to electromagnetic fields. ![]() 6,7 Aussillous and Quéré were the first to report liquid marbles in laboratory. To mitigate this, aphids coat the sticky secretions with wax particles to produce ∼0.1 mm-diameter non-sticky marbles for waste disposal. Curiously, aphids residing inside confined plant galls prepare liquid marbles to preempt life-threatening risks of getting wet by their own sugary secretions. Thus, a liquid marble is a “non-wetting soft object” 5 that rolls and bounces like a marble when gently displaced. 1–4 This arrangement prevents direct contact between the liquid and underlying substrate. Introduction Liquid marbles are commonly composed of water droplets covered with a layer of hydrophobic particles. Altogether, these findings advance our fundamental understanding of liquid marbles and should contribute to the rational development of technologies. Furthermore, this model and the general framework can provide mechanistic insights into extant literature on the evaporation of liquid marbles. ![]() The model fits are in excellent agreement with our experimental results. Based on these insights, we developed an evaporation model for liquid marbles that takes into account their time-dependent shape evolution. We demonstrate that the potential final states of evaporating liquid marbles are characterized by one of the following: (I) constant surface area, (II) particle ejection, or (III) multilayering. ![]() To unentangle the contributions of particle size, roughness, friction, and chemical make-up, we investigated the evaporation of liquid marbles formed with particles of sizes varying over 7 nm–300 μm and chemical compositions ranging from hydrophilic to superhydrophobic. Here, we have combined complementary experiments and theory to fill this gap. For instance, analytical approaches for modeling the evaporation of liquid marbles exploit empirical parameters that are not based on liquid–particle and particle–particle interactions. Despite the considerable cross-disciplinary interest and value of the research on liquid marbles, a unified framework for describing the mechanics of deflating liquid marbles-as the liquid evaporates-is unavailable. These squishy objects bounce, coalesce, break, inflate, and deflate while the liquid does not touch the substrate underneath. They are observed in nature and have practical significance. Liquid marbles refer to droplets that are covered with a layer of non-wetting particles. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |