Liquid Metal Vacuoles

Abstract

In the field of interfacial science, the formation, maintenance and rupture theory of bubble gas-liquid two-phase interface has been an important basic scientific issue. Compared to soapy water, it is impossible to blow bubbles only with pure water since the interaction between water molecules is too strong, making it more inclined to form water droplets. The addition of soap makes it easier to form and maintain bubbles. However, even with the help of surfactants, beautiful soap bubbles are fleeting and rather easily destroyed. This is because the bubble is a thermodynamically unstable system with a high surface Gibbs function. [4] When the bubble is formed, the gas-liquid interface area and the interfacial free energy of the system increases. Therefore, the formation of bubbles is a thermodynamically nonspontaneous process that requires external work on the system. Overall, the addition of surfactants can reduce the gas-liquid interfacial tension, thus reducing the energy consumption when blowing bubbles, which is beneficial to the formation and stability of bubbles. [5] In addition, the more important role of the surfactant lies in that its molecules can form an oriented monolayer on the gas-liquid interface, with the polar end points to the water. The more tightly the surfactants are arranged on the fluid surface, the firmer the interfacial film and the more stable the bubbles.Water is usually adopted in traditional bubble studies because of its inherently low surface tension (≈70 mN m −1 ) and the ability of surfactants to further reduce the surface tension. While in this work, we propose to introduce a high-surface-tension liquid metal (LM) fluid and study the formation of membrane structure in a solution (S) environment. Among the many possible LM candidates, gallium-based low-melting-point LM has received extensive attention in recent years, since it combines the virtues of liquid, such as fluidity, flexibility, and deformability with the advantages of metals, like high electrical conductivity and heat conductivity. [6] Besides, gallium-based alloys are nontoxic and all components have a very low vapor pressure at elevated temperature, which permits safe handling. [7] Owing to these outstanding merits, LM is believed to be an alternative material to realize numerous functions and has therefore been applied in a variety of significant areas, [8][9][10] including device cooling, flexible electronics, deformable antennas, biomedical technology, 3D print, etc. Besides, LM has been found to display a wealth of surface and interface phenomena since such a Conventional bubbles are generally made of an outside water film and the interior air, and their formation and rupture involve rich scientific knowledge. An intriguing question is what would happen if the water film and air of such bubbles were replaced by completely different fluids? Here, a high-surfacetension liquid metal-solution bilayer is introduced into the two-phase interface system, and a new conceptual hybrid vacuole consisting of a liquid metal outer...

Mechanism of Oil-in-Liquid Metal Emulsion Formation

“…For example, LM readily breaks up into microdroplets when mixed with a similar volume of another liquid (e.g., silicone oil). 43−46 Smaller volumes of air, 47,48 silicone oil, water, peroxide, hydrochloric acid, and sodium hydroxide 48,49 can be directly injected into a larger pool of LM but rapidly escape due to large buoyancy forces. Interestingly, the environment above the LM pool can be adjusted to promote or inhibit oxide or surfactant "shell" formation and trap either very small (∼5−10 μm) 50 or very large (∼1 cm) droplets of several fluids right under the external LM surface.…”

“…Interestingly, the environment above the LM pool can be adjusted to promote or inhibit oxide or surfactant "shell" formation and trap either very small (∼5−10 μm) 50 or very large (∼1 cm) droplets of several fluids right under the external LM surface. 48,49 However, these neat fluidic structures are restricted to the surface region or are temporary, so they are of limited use in practical applications. In contrast, silicone oil with a viscosity below ∼1000 cSt can be manually dispersed into microscale droplets (∼5−500 μm) within LM foams to create lasting emulsions.…”

“…Without oxide formation, LM’s enormous surface tension (∼8 times that of water), high density (∼6 times that of water), and low viscosity (∼2 times that of water) make the addition of secondary fluids challenging. For example, LM readily breaks up into microdroplets when mixed with a similar volume of another liquid (e.g., silicone oil). − Smaller volumes of air, , silicone oil, water, peroxide, hydrochloric acid, and sodium hydroxide , can be directly injected into a larger pool of LM but rapidly escape due to large buoyancy forces. Interestingly, the environment above the LM pool can be adjusted to promote or inhibit oxide or surfactant “shell” formation and trap either very small (∼5–10 μm) or very large (∼1 cm) droplets of several fluids right under the external LM surface. , However, these neat fluidic structures are restricted to the surface region or are temporary, so they are of limited use in practical applications.…”

“…For example, LM readily breaks up into microdroplets when mixed with a similar volume of another liquid (e.g., silicone oil). − Smaller volumes of air, , silicone oil, water, peroxide, hydrochloric acid, and sodium hydroxide , can be directly injected into a larger pool of LM but rapidly escape due to large buoyancy forces. Interestingly, the environment above the LM pool can be adjusted to promote or inhibit oxide or surfactant “shell” formation and trap either very small (∼5–10 μm) or very large (∼1 cm) droplets of several fluids right under the external LM surface. , However, these neat fluidic structures are restricted to the surface region or are temporary, so they are of limited use in practical applications. In contrast, silicone oil with a viscosity below ∼1000 cSt can be manually dispersed into microscale droplets (∼5–500 μm) within LM foams to create lasting emulsions .…”

Liquid Metal Combinatorics toward Materials Discovery

“…[145] Liquids can also be injected into liquid metal to form liquid metal vacuoles. [146] The size and maintenance time of the liquid metal vacuoles can be adjusted by varying the solution environment and composition of the injecting solution. This metastable state of the hybrid fluid interface leads to several interesting phenomena, such as interfacial flow and clear drapes.…”