When illuminated by a laser, plasmonic nanoparticles immersed in water can very quickly and strongly heat up, leading to the nucleation of so-called plasmonic vapor bubbles. While the long-time behavior of such bubbles has been well-studied, here, using ultrahigh-speed imaging, we reveal the nucleation and early life phase of these bubbles. After some delay time from the beginning of the illumination, a giant bubble explosively grows, and collapses again within 200 μs (bubble life phase 1). The maximal bubble volume $V_{max}$ remarkably increases with decreasing laser power, leading to less total dumped energy E. This dumped energy shows a universal linear scaling relation with $V_{max}$, irrespective of the gas concentration of the surrounding water. This finding supports that the initial giant bubble is a pure vapor bubble. In contrast, the delay time does depend on the gas concentration of the water, as gas pockets in the water facilitate an earlier vapor bubble nucleation, which leads to smaller delay times and lower bubble nucleation temperatures. After the collapse of the initial giant bubbles, first, much smaller oscillating bubbles form out of the remaining gas nuclei (bubble life phase 2). Subsequently, the known vaporization dominated growth phase takes over, and the bubble stabilizes (life phase 3). In the final life phase 4, the bubble slowly grows by gas expelling due to heating of the surrounding. Our findings on the explosive growth and collapse during the early life phase of a plasmonic vapor bubble have strong bearings on possible applications of such bubbles. Significance Plasmonic microbubbles are at the center of numerous applications, including micromanipulation/nanomanipulation, biomedical diagnosis and therapy, and solar energy harvesting. Controlling the dynamics of these microbubbles is key to successfully exploiting their potential in the growing number of applications. Literature has vastly overlooked the nucleation and early microsecond dynamics by which these microbubbles arise. It is of utmost importance to understand this early phase, as it displays the most violent dynamics and is the precursor and origin of all subsequent dynamics, on which the many applications rely.

High-velocity impact welding is a kind of solid-state welding process that is one of the solutions for the joining of dissimilar materials that avoids intermetallics. Five main methods have been developed to date. These are gas gun welding (GGW), explosive welding (EXW), magnetic pulse welding (MPW), vaporizing foil actuator welding (VFAW), and laser impact welding (LIW). They all share a similar welding mechanism, but they also have different energy sources and different applications. This review mainly focuses on research related to the experimental setups of various welding methods, jet phenomenon, welding interface characteristics, and welding parameters. The introduction states the importance of high-velocity impact welding in the joining of dissimilar materials. The review of experimental setups provides the current situation and limitations of various welding processes. Jet phenomenon, welding interface characteristics, and welding parameters are all related to the welding mechanism. The conclusion and future work are summarized.

Under continuous laser irradiation, noble metal nanoparticles immersed in water can quickly heat up, leading to the nucleation of so-called plasmonic bubbles. In this work we want to further understand the bubble nucleation and growth mechanism. In particular, we quantitatively study the effect of the amount of the dissolved air on the bubble nucleation and growth dynamics, both for the initial giant bubble, which forms shortly after switching on the laser and which is mainly composed of vapor, and for the final life phase of the bubble, during which it mainly contains air expelled from the water. We found that the bubble nucleation temperature depends on the gas concentration: the higher the gas concentration, the lower the bubble nucleation temperature. Also the long-term diffusion dominated bubble growth is governed by the gas concentration. The radius of the bubbles grows as R(t)∝t^1/3 for air equilibrated and for air oversaturated water. In contrast, in partially degassed water, the growth is much slower, since even for the highest temperature we achieve, the water remains under-saturated.

Significance: Plasmonic bubbles are relevant in biomedical diagnosis and therapy, catalysis, and micro- and nanomanipulation. Hitherto, their behavior has mainly been analyzed in pure liquids. However, in general, these applications of plasmonic bubbles take place in binary or multicomponent liquids. Here we show that plasmonic bubbles in a binary liquid display surprising phenomena, resulting from the emerging complicated physicochemical hydrodynamics of a vapor bubble in such binary liquids. Depending on the application, these phenomena can be either a benefit or a hindrance. Our results are also relevant for other bubble nucleation processes in multicomponent liquids, such as boiling, electrolysis, or catalysis.

Spherical-cap-shaped interfacial nanobubbles (NBs) forming on hydrophobic surfaces in aqueous solutions have extensively been studied both from a fundamental point of view and due to their relevance for various practical applications. In this study, the nucleation mechanism of spontaneously generated NBs at solid–liquid interfaces of immersed nanostructured hydrophobic surfaces is studied. Depending on the size and density of the surface nanostructures, NBs with different size and density were reproducibly and deterministically obtained. A two-step process can explain the NB nucleation, based on the crevice model, i.e., entrapped air pockets in surface cavities which grow by diffusion. The results show direct evidence for the spontaneous formation of NBs on a surface at its immersion. Next, the influence of size and shape of the nanostructures on the nucleated NBs are revealed. In particular, on non-circular nanopits we obtain NBs with a non-circular footprint, demonstrating the strong pinning forces at the three-phase contact line.

The understanding of the shrinkage dynamics of plasmonic bubbles formed around metallic nanoparticles immersed in liquid and irradiated by a resonant light source is crucial for the usage of these bubbles in numerous applications. In this paper we exper- imentally show and theoretically explain that a plasmonic bubble during its shrinkage undergoes two different phases: first, a rapid partial bubble shrinkage governed by vapor condensation and, second, a slow diffusion-controlled bubble dissolution. The history of the bubble formation plays an important role in the shrinkage dynamics during the first phase, as it determines the gas-vapor ratio in the bubble composition. Higher laser powers lead to more vaporous bubbles, while longer pulses and higher dis- solved gas concentrations lead to more gaseous bubbles. The dynamics of the second phase barely depends on the history of bubble formation, i.e. laser power and pulse duration, but strongly on the dissolved gas concentration, which defines the concentra- tion gradient at the bubble interface. Finally, for the bubble dissolution in the second phase, with decreasing dissolved gas concentration, we observe a gradual transition from a R(t) ∽ (t₀ - t)^1/3 scaling law to a R(t) ∽ (t₀ - t)^1/2 scaling law, where t₀ is the lifetime of the bubble and theoretically explain this transition.