Inducing drop to bubble transformation via resonance in ultrasound

Abstract

Bubble formation plays an important role in industries concerned with mineral flotation, food, cosmetics, and materials, which requires additional energy to produce the liquid–gas interfaces. A naturally observed fact is, owing to the effect of surface tension, a bubble film tends to retract to reduce its surface area. Here we show a “reverse” phenomenon whereby a drop is transformed into a bubble using acoustic levitation via acoustic resonance. Once the volume of the cavity encapsulated by the buckled film reaches a critical value V*, resonance occurs and an abrupt inflation is triggered, leading to the formation of a closed bubble. Experiments and simulations both reveal that V* decreases with increasing acoustic frequency, which agrees well with acoustic resonance theory. The results afford enlightening insights into acoustic resonance and highlight its role in manipulating buckled fluid–fluid interfaces, providing a reference for fabricating unique core–shell-like materials.

Power generation from the interaction of a liquid droplet and a liquid membrane

“…The penetrability, shape adaptability, and self-healing ability of the liquid membrane can effectively maintain a smooth separation of two liquids. The liquid membrane typically shows dynamic reconfigurability 21 , stability, and elasticity 22 , which can be used for antifouling transport 23 , unusual particle separators 24 , biomedical fluid handling 25 and so on. In recent years, such membranes have been shown to have extensive applications in biochemistry and medicine 26 , environmental management, fossil fuel extraction, cosmetics and other industries.…”

Evaporation and drying kinetics of water-NaCl droplets via acoustic levitation

“…14 Zang et al used ALM to generate bubbles for industries pertaining to inorganic salts, food, cosmetics, and materials. 15,16 Furthermore, these authors also developed a microreactor that coats solid potassium permanganate on the surface of levitated water droplets. 17,18 Xie et al demonstrated that small organisms such as insects and small sh can levitate in a living state.…”

Evaporation of droplet in mid-air: Pure and binary droplets in single-axis acoustic levitator

“…The container-less nature of ALM makes this technique widely applicable in the fields of material processing, biology, and analytical chemistry, since such container-less processing can prevent nucleation and contamination due to contact with container walls [2–9]. For example, Zang et al applied ALM to the formation of bubbles for use in food, cosmetics, pharmaceuticals, ultra-light materials, and mineral flotation [10,11], additionally examining the spreading of potassium permanganate on the surface of levitated water droplets to develop a microreactor [12,13]. Xie et al demonstrated that small organisms, such as insects and small fish can be acoustically levitated as well [14].…”