Surface nanobubbles: Theory, simulation, and experiment. A review

Abstract

Surface nanobubbles (NBs) are stable gaseous phases in liquids that form at the interface with solid substrates. They have been particularly intriguing for their high stability that contradicts theoretical expectations and their potential relevance for many technological applications. Here, we present the current state of the art in this research area by discussing and contrasting main results obtained from theory, simulation and experiment, and presenting their limitations.We also provide future perspectives anticipating that this review will stimulate further studies in the research area of surface NBs.The subsequent sections of this review article are organised as follows: In Sec. 2, we present a range of different theoretical, simulation and experimental methodologies, which are used to study surface NBs discussing their limitations and contrasting main results. In Sec. 3, we discuss the main morphological and mechanical characteristics of surface NBs. In Sec. 4, we provide a review of the main experimental methods to generate surface NBs. In Sec. 5, we discuss the main hypothesis that supports the intriguing high NBs' stability, i.e. contactline pinning. Finally, we present our perspectives in the research area of surface NBs in Sec. 6.

Proving and interpreting the spontaneous formation of bulk nanobubbles in aqueous organic solvent solutions: effects of solvent type and content

“…[8][9][10][11][12][13][14][15] A similar debate which lasted for many years took place after surface nanobubbles emerged and became the focus of attention about two decades ago. 16 The present situation is exacerbated by the lack of a full rational explanation of the mechanism behind the long-term stability of BNBs. 6,[17][18][19] A number of speculative interpretations have been postulated but a complete physical model has yet to emerge.…”

The effect of ultrasound on bulk and surface nanobubbles: A review of the current status

“…Some researchers have summarized and reviewed different stability theories or models of bulk and surface nanobubbles in recent years [2] , [5] , [6] . However, there is no effective research on the stability mechanisms of bulk and surface nanobubbles in an acoustic field.…”

“…Nanobubbles include bulk and surface nanobubbles. Surface nanobubbles are described as spherical caps that are a few nanometers to tens of nanometers high and about 1 μm wide [5] , [6] . They are well studied in the literature and proven to be gas filled entities [7] , [8] , although the origin of their stability is still in dispute [9] , [10] , [11] , [12] , [13] , [14] , [15] .…”

“…Temperature changes and ethanol water are the most commonly used methods to produce surface nanobubbles [41] , [42] . The formation of nanobubbles or microbubbles on a solid surface immersed in water is dependent on surface heterogeneities [5] , [6] . There are many preexisting gas cavities on hydrophobic solid surfaces, which can be due to the presence of physical “defect points,” normally termed “grooves” or “crevices,” on solid surfaces [43] , [44] .…”

Surface nanodrops and nanobubbles: a classical density functional theory study

“…In particular, using a model disjoining pressure, Svetovoy et al (2016) recently showed that surface-interface interactions significantly affect the shapes and contact angles of nanobubbles. Recent reviews by Theodorakis & Che (2019), Qian, Arends & Zhang (2019) and Lohse & Zhang (2015) discuss the latest experimental approaches, simulation studies and capillary models of surface nanodrops and nanobubbles. Interesting and promising fully microscopic approaches for computing the disjoining pressure of adsorbed liquid films were recently developed by MacDowell (2011), MacDowell et al (2014) and Nold et al (2014).…”