Viscosity and rheological behavior of microbubbles in capillary tubes

Graphene-Loaded Aphron Microbubbles for Enhanced Drilling Fluid Performance and Carbon Capture and Storage

Maintaining the stability of microbubbles is essential for enhancing the longevity of aphronic water-based drilling fluid usage in drilling depleted reservoirs and other under-pressured zones. Here, we introduce the integration of partially reduced graphene oxide (PrGO) nanosheets into the shell of aphron microbubbles (AMBS) to enhance the stability and size distribution, particularly for drilling fluid applications and carbon geological storage. The amphiphilic characteristic of PrGO nanosheets, due to meticulous control of the reduction process of graphene oxide, facilitates their spontaneous adsorption at interfaces, thereby reducing the interfacial energy as a two-dimensional surfactant. The loading of PrGO nanosheets in the polymeric shell of AMBs enhances mechanical strength, stability, and resistance to gas diffusion, prolonging the half-life of the microbubbles to over 120%. According to the results, a more uniform size distribution and reduction of microbubble size up to 60% have been achieved at a concentration of 0.30 wt % PrGO. Rheological studies using various models indicate the optimal PrGO concentration for improved stability in aphronic fluids. Filtration tests indicate the loaded PrGO can reduce filtration loss by up to 45% at 0.50 wt % by forming a cohesive and compressible cake, improving filtration control. Changes in the Fourier-transform infrared spectra and contact angle measurements suggest increased surface hydrophobicity with higher graphene concentrations in aphronic fluid cakes. Moreover, the study elucidates that the stability of microbubbles is influenced by the type of core gas, with N2 gas yielding the highest stability and CO2 the lowest. Ultimately, these results highlight the beneficial effect of incorporation of PrGO nanosheets in aphron microbubbles to boost the drilling fluid performance and efficiency, which will pave the way toward ultralightweight fluids that can even be used as carrier and injection fluids in carbon capture and leak-free geological storage technologies.

Growth of Laser-Induced Microbubbles inside Capillary Tubes Affected by Gathered Light-Absorbing Particles

Microbubbles have important applications in optofluidics. The generation and growth of microbubbles is a complicated process in microfluidic channels. In this paper, we use a laser to irradiate light-absorbing particles to generate microbubbles in capillary tubes and investigate the factors affecting microbubble size. The results show that the key factor is the total area of the light-absorbing particles gathered at the microbubble bottom. The larger the area of the particles at bottom, the larger the size of the microbubbles. Furthermore, the area is related to capillary tube diameter. The larger the diameter of the capillary tube, the more particles gathered at the bottom of the microbubbles. Numerical simulations show that the Marangoni convection is stronger in a capillary tube with a larger diameter, which can gather more particles than that in a capillary tube with a smaller diameter. The calculations show that the particles in contact with the microbubbles will be in a stable position due to the surface tension force.

The Role of Ultrasound-Driven Microbubble Dynamics in Drug Delivery: From Microbubble Fundamentals to Clinical Translation

In the last couple of decades, ultrasound-driven microbubbles have proven excellent candidates for local drug delivery applications. Besides being useful drug carriers, microbubbles have demonstrated the ability to enhance cell and tissue permeability and, as a consequence, drug uptake herein. Notwithstanding the large amount of evidence for their therapeutic efficacy, open issues remain. Because of the vast number of ultrasound- and microbubble-related parameters that can be altered and the variability in different models, the translation from basic research to (pre)clinical studies has been hindered. This review aims at connecting the knowledge gained from fundamental microbubble studies to the therapeutic efficacy seen in in vitro and in vivo studies, with an emphasis on a better understanding of the response of a microbubble upon exposure to ultrasound and its interaction with cells and tissues. More specifically, we address the acoustic settings and microbubble-related parameters (i.e., bubble size and physicochemistry of the bubble shell) that play a key role in microbubble-cell interactions and in the associated therapeutic outcome. Additionally, new techniques that may provide additional control over the treatment, such as monodisperse microbubble formulations, tunable ultrasound scanners, and cavitation detection techniques, are discussed. An in-depth understanding of the aspects presented in this work could eventually lead the way to more efficient and tailored microbubble-assisted ultrasound therapy in the future.