Diffusively Controlled Growth of Nanobubbles under Contact Line Pinning: Implication of Nanoscale Flow and Heat Controls by Nanobubbles

Abstract

More and more micro/nanofluidic devices are proposed to improve the performance in thermal and medical applications, and nanobubbles promise a new way of controlling the heat and flow at high spatial and temporal resolutions. The long lifetime of static nanobubbles has been extensively investigated in both experiments and theoretical modeling, but the dynamic growth of nanobubbles lacks comprehensive understanding. Therefore, we conduct an experimental investigation of nanobubble growth in a graphene liquid cell, under oversaturation conditions of dissolved hydrogen gas by electron beam radiolysis of water, via in situ transmission electron microscopy (in situ liquid cell TEM). We analyze characteristic parameters of nanobubble growth, including radius, volume, extension length, nanobubble shape, contact angle, and growth rate, based on the TEM images. We demonstrate that the growth of individual nanobubbles is determined by the oversaturation level of dissolved gas and follows a diffusively controlled dynamic as described by the Epstein–Plesset model. With the information from 3D reconstruction of nanobubbles, we reveal that both growth rate and local contact angle are affected by contact line pinning. Overall, we present a comprehensive analysis of a diffusively controlled nanobubble growth subjected to dissolved hydrogen gas concentrations and contact line pinning through the growth rate, nanobubble shape, and contact angle.

Single-Digit Nanobubble Sensing via Nanopore Technology

“…6 Notably, nanobubbles exhibit unique fluid dynamic characteristics, particularly their flowing features in mixing and mass transfer processes, rendering them distinctive and valuable in various applications. 7 Existing techniques for detecting nanobubbles in solution encompass fluorescence microscopy, 8 atomic force microscopy (AFM), 9,10 scanning electron microscopy (SEM), 11 nanoparticle tracking analysis (NTA), 12 and dynamic light scattering (DLS), 13 all of which are suitable for high-resolution sensing applications. Some interesting studies show that bubbles have different sizes in acidic and alkaline solutions by various methods.…”

“…For example, nanobubbles serve as carriers, transporting therapeutic agents to specific targets, facilitating pollutant removal for surface cleaning, and aiding nutrient delivery to enhance plant absorption . Notably, nanobubbles exhibit unique fluid dynamic characteristics, particularly their flowing features in mixing and mass transfer processes, rendering them distinctive and valuable in various applications …”

Surface Morphology Enriching the Energy Barrier Leads to the Adsorption Characteristic of Nanobubbles

“…Surface or interfacial nanobubbles (INBs) refer to the gas domains that exist at the solid–liquid interface, typically tens of nanometers in height and hundreds of nanometers in lateral sizes. − Surface nanobubbles have garnered much attention due to their potential applications in different fields, such as fluid slip, − foam flotation, − drug delivery, ultrasound tumor imaging enhancement, and surface cleaning and antifouling. − Understanding the mechanism of formation and the stability of surface nanobubbles is crucial for fundamental research. Surface nanobubbles have been experimentally observed to survive for hours or days, − which defies the classical Laplace theory. , This anomalous stability can be explained by the contact line pinning effect, − which suggests that the contact lines of interfacial nanobubbles are fixed, and therefore the gas diffusion rate within the nanobubbles is limited, thus prolonging the nanobubble lifetime. Dayong Li reported that nanobubbles on the convex and uneven nanostructured polystyrene (PS) surface were anchored between nanobumps, producing a pinning effect that maintained the stability of the nanobubbles.…”