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Bubbles oscillating in the presence of ultrasound is commonly employed in biomedical applications for drug delivery, ultrasound enhanced thrombolysis, and the transport and manipulation of cells. This is possible because bubbles tend to interact with the ultrasound to undergo periodic shape changes known as shape-mode oscillation, concomitant with the generation of liquid agitation or streaming. This phenomenon is examined both experimentally and theoretically on a single bubble at a frequency of (45 1) kHz. Effects of ultrasonic frequency and power on the flowfield were explored. Experiments revealed different trends in the development of liquid streaming velocities at different acoustic forcing conditions (5.53, 6.80 and 7.02 Vpp), with lowest (0.5 mm/s) and highest (1.1 mm/s) values of time-averaged mean streaming velocity occurring at 6.80 Vpp and 7.02 Vpp, respectively. Simulations captured the simultaneous evolution of bubble-shapes that helped create flow vortices in the liquid surrounding the bubble. These vortices collectively responsible in generating signature patterns in the liquid for a dominant shape-mode of the bubble, and could also generate localised shear stresses for practical application. The velocity and pressure profiles in the liquid around the bubble confirmed the connection of the applied and reflected soundwaves in driving this phenomenon.

Brown seaweed Ecklonia radiata harbors valuable polyphenols, notably phlorotannins, prized for their health benefits. This study optimized phlorotannin extraction via conventional solvent extraction and ultrasound-assisted extraction methods, utilizing variable concentrations of ethanol. Employing fractional factorial designs, key variables were identified. Steepest ascent/descent method and central composite rotatable designs refined optimal conditions, enhancing phlorotannin and polyphenol yields, and antioxidant capacities. Under optimized conditions, phlorotannin contents reached 2.366 ± 0.01 and 2.596 ± 0.04 PGE mg/g, total polyphenol contents peaked at 10.223 ± 0.03 and 10.836 ± 0.02 GAE mg/g. Robust antioxidant activity was observed: DPPH and OH radical scavenging capacities measured 27.891 ± 0.06 and 17.441 ± 0.08 TE mg/g, and 37.498 ± 1.12 and 49.391 ± 0.82 TE mg/g, respectively. Reducing power capacities surged to 9.016 ± 0.02 and 28.110 ± 0.10 TE mg/g. Liquid chromatography-mass spectrometry (LC-MS) and high-performance liquid chromatography (HPLC) analyses revealed enriched antioxidant compounds. Variations in polyphenol profiles were noted, potentially influencing antioxidant capacity nuances. This study illuminated the potential of E. radiata potential as a polyphenol source and offers optimized extraction methods poised to benefit various industries.

An alternative method to efficiently synthesize Core‐Crosslinked Star polymers (arm‐first approach) is described in this work. The star polymers are produced utilizing a two‐step, one‐pot Sono‐RAFT process. N,N′‐dimethylacrylamide (DMA) is used to prepare the arms, whereas N,N′‐methylenebis(acrylamide) (MAA) is employed as the crosslinking agent. The reactions were conducted in an aqueous medium at room temperature. Using the sono‐RAFT approach, polymerization under different applied powers, crosslinker to arm ratios, and degrees of polymerization were investigated to determine the optimal reaction conditions for synthesizing star polymers. By altering the applied power, the reaction time can be decreased by half. Using a triblock arm, a CCS polymer was produced, and the resulting polymer demonstrated a very high arm‐to‐star conversion.

Ultrasonic waves in a liquid media generate both chemical and mechanistic effects that are actively used to perform chemical reactions, polymer synthesis, nanoparticle synthesis, colloids, food processing and so on. The application of sonochemistry in polymer science has been an interesting topic of research in the recent years. Ultrasonication acts as an external stimulus to initiate free radical polymerization (FRP) by the homolysis of the solvent, thereby generating radicals. The recent utilization of high frequency ultrasound (>100 KHz) for polymer synthesis has evoked new interest in the use of sonochemistry in the field of polymer chemistry, especially in chain growth polymerization reactions including reversible-deactivation radical polymerization (RDRP) techniques and novel applications. This review presents the principles of sonochemisty and the fundamental aspects governing the cavitation process and the radical generation process. A historical overview of the development of ultrasound-assisted polymerization with a focus on chain-growth polymerizations operating under pseudo-“living” conditions including nitroxide-mediated polymerization (NMP), atom transfer radical polymerization (ATRP) and reversible addition–fragmentation chain transfer (RAFT) polymerization is provided. The utilization of ultrasound in polymer applications such as hydrogels, biomedical nanostructures, drug delivery, nanocomposite synthesis is also discussed. Unlike conventional FRP, ultrasound-initiated polymerization does not involve any external toxic chemical initiators, adds temporal control to the polymerization process, offers excellent control over the molecular weight and the microstructure of the final polymers, etc. The ultrasound assisted polymerization is a novel, clean and green technology, which can be investigated further by coupling with thermo-, mechano- or photochemical stimuli or flow chemistry. It has the potential to be scaled up into an industrial process.