The Experts below are selected from a list of 1440 Experts worldwide ranked by ideXlab platform
Detlef Lohse - One of the best experts on this subject based on the ideXlab platform.
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Dynamics of Formation of a Vapor Nanobubble Around a Heated Nanoparticle
Journal of Physical Chemistry C, 2018Co-Authors: Shantanu Maheshwari, Martin A. Van Der Hoef, Andrea Prosperetti, Detlef LohseAbstract:We study the formation of a Nanobubble around a heated nanoparticle in a bulk liquid by using molecular dynamics simulations. The nanoparticle is kept at a temperature above the critical temperature of the surrounding liquid, leading to the formation of a vapor Nanobubble attached to it. First, we study the role of both the temperature of the bulk liquid far away from the nanoparticle surface and the temperature of the nanoparticle itself on the formation of a stable vapor Nanobubble. We determine the exact conditions under which it can be formed and compare this with the conditions that follow from a macroscopic heat balance argument. Next, we demonstrate the role of dissolved gas on the conditions required for nucleation of a Nanobubble and on its growth dynamics. We find that beyond a certain threshold concentration, the dissolved gas dramatically facilitates vapor bubble nucleation due to the formation of gaseous weak spots in the surrounding liquid.
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the nucleation rate of single o2 Nanobubbles at pt nanoelectrodes
Langmuir, 2018Co-Authors: Alvaro Moreno Soto, Sean R German, Martin A Edwards, Devaraj Van Der Meer, Detlef Lohse, Henry S. WhiteAbstract:Nanobubble nucleation is a problem that affects efficiency in electrocatalytic reactions since those bubbles can block the surface of the catalytic sites. In this article, we focus on the nucleation rate of O2 Nanobubbles resulting from the electrooxidation of H2O2 at Pt disk nanoelectrodes. Bubbles form almost instantaneously when a critical peak current, inbp, is applied, but for lower currents, bubble nucleation is a stochastic process in which the nucleation (induction) time, tind, dramatically decreases as the applied current approaches inbp, a consequence of the local supersaturation level, ζ, increasing at high currents. Here, by applying different currents below inbp, Nanobubbles take some time to nucleate and block the surface of the Pt electrode at which the reaction occurs, providing a means to measure the stochastic tind. We study in detail the different conditions in which Nanobubbles appear, concluding that the electrode surface needs to be preconditioned to achieve reproducible results. We ...
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the nucleation rate of single mathrm o_2 Nanobubbles at pt nanoelectrodes
Langmuir, 2018Co-Authors: A Morenosoto, Sean R German, Martin A Edwards, Devaraj Van Der Meer, Detlef Lohse, Henry S. WhiteAbstract:Nanobubble nucleation is a problem that affects efficiency in electrocatalytic reactions, since those bubbles can block the surface of the catalytic sites. In this article, we focus on the nucleation rate of $\mathrm{O_2}$ Nanobubbles resulting from electrooxidation of $\mathrm{H_2O_2}$ at Pt disk nanoelectrodes. Bubbles form almost instantaneously when a critical peak current, $i_\mathrm{nb}^\mathrm{p}$, is applied, but for lower currents, bubble nucleation is a stochastic process in which the nucleation (induction) time, $t_\mathrm{ind}$, dramatically decreases as the applied current approaches $i_\mathrm{nb}^\mathrm{p}$, a consequence of the local supersaturation level, $\zeta$, increasing at high currents. Here, by applying different currents below $i_\mathrm{nb}^\mathrm{p}$, Nanobubbles take some time to nucleate and block the surface of the Pt electrode at which the reaction occurs, providing a means to measure the stochastic $t_\mathrm{ind}$. We study in detail the different conditions in which nan...
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Leakiness of Pinned Neighboring Surface Nanobubbles Induced by Strong Gas–Surface Interaction
2018Co-Authors: Shantanu Maheshwari, Marti Van Der Hoef, Javier Rodrı́guez Rodrı́guez, Detlef LohseAbstract:The stability of two neighboring surface Nanobubbles on a chemically heterogeneous surface is studied by molecular dynamics (MD) simulations of binary mixtures consisting of Lennard-Jones (LJ) particles. A diffusion equation-based stability analysis suggests that two Nanobubbles sitting next to each other remain stable, provided the contact line is pinned, and that their radii of curvature are equal. However, many experimental observations seem to suggest some long-term kind of ripening or shrinking of the surface Nanobubbles. In our MD simulations we find that the growth/dissolution of the Nanobubbles can occur due to the transfer of gas particles from one Nanobubble to another along the solid substrate. That is, if the interaction between the gas and the solid is strong enough, the solid–liquid interface can allow for the existence of a “tunnel” which connects the liquid–gas interfaces of the two Nanobubbles to destabilize the system. The crucial role of the gas–solid interaction energy is a nanoscopic element that hitherto has not been considered in any macroscopic theory of surface Nanobubbles and may help to explain experimental observations of the long-term ripening
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Nanobubble formation on a warmer substrate
Soft Matter, 2014Co-Authors: Shuhua Peng, Detlef Lohse, Greg G Qiao, Voytek Gutowski, Xuehua ZhangAbstract:The solvent exchange procedure is an often-used protocol to produce surface Nanobubbles. In this procedure, the substrate is exposed to a good solvent for gas which is then mixed and rinsed with a poor solvent for gas and the Nanobubbles form on the solid–liquid interface. Here we study the effects of temperatures of the substrate and the first solvent on Nanobubble formation. Atomic force microscopy with temperature control was used to examine the formation of Nanobubbles at temperatures between 37 C and 54 C. It was found that the probability of Nanobubble formation was larger on substrates at higher temperatures. Moreover, on warmer substrates we found Nanobubbles with lateral extensions up to 8 mm. A morphologic analysis shows that all Nanobubbles, including giant Nanobubbles, have a similar aspect ratio, independent of the substrate temperature, and that this aspect ratio corresponds to a contact angle between 13 and 22 (on the gas side), much smaller than the macroscopic counterparts. We finally discuss the implications of our results for various theories on Nanobubble stability.
Agata A Exne - One of the best experts on this subject based on the ideXlab platform.
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time intensity curve analysis and tumor extravasation of Nanobubble ultrasound contrast agents
Ultrasound in Medicine and Biology, 2019Co-Authors: Eric C Abenoja, Reshani Perera, Al De Leo, Tianzhi A, Agata A ExneAbstract:Abstract Our group recently presented a simple strategy using the non-ionic surfactant, Pluronic, as a size control excipient to produce Nanobubbles in the 100-nm range, which exhibited stability and echogenicity on par with clinically available microbubbles. The objective of the present study was to evaluate biodistribution and extravasation of the Pluronic-stabilized lipid Nanobubbles compared with microbubbles in 2 experimental tumor models in mice. Standard lipid-stabilized perfluoropropane bubbles (Pluronic L10) and lipid-stabilized perfluoropropane Nanobubbles were intravenously injected into mice bearing either an orthotopic mouse breast cancer (BC4 T1) or subcutaneous mouse ovarian cancer (OVCAR-3) through the tail vein to perform perfusion dynamic studies. No significant differences between the Nanobubble and microbubble groups were observed in the peak enhancement of the 3 tested regions (tumor, liver and kidney). However, the decay rates of Nanobubble in the tumor and kidney of BC4 T1-bearing mice, as well as in mice with OVRCAR-3 tumors were significantly slower than those of the microbubble. To quantify extravasation, fluorescently labeled bubbles were intravenously injected into mice bearing the same tumors. Histologic analysis showed that Nanobubbles were retained in tumor tissue to a greater extent compared with microbubbles in both tumor models at the 3-h time point. Our results demonstrate unique Nanobubble behavior compared with microbubbles and support augmented application of these agents in ultrasound molecular imaging and drug delivery beyond the tumor vasculature.
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cryo em visualization of lipid and polymer stabilized perfluorocarbon gas Nanobubbles a step towards Nanobubble mediated drug delivery
Scientific Reports, 2017Co-Authors: Christophe Hernandez, Sahil Gulati, Gabriella Fioravanti, Phoebe L Stewa, Agata A ExneAbstract:Gas microbubbles stabilized with lipids, surfactants, proteins and/or polymers are widely used clinically as ultrasound contrast agents. Because of their large 1–10 µm size, applications of microbubbles are confined to the blood vessels. Accordingly, there is much interest in generating nanoscale echogenic bubbles (Nanobubbles), which can enable new uses of ultrasound contrast agents in molecular imaging and drug delivery, particularly for cancer applications. While the interactions of microbubbles with ultrasound have been widely investigated, little is known about the activity of Nanobubbles under ultrasound exposure. In this work, we demonstrate that cryo-electron microscopy (cryo-EM) can be used to image nanoscale lipid and polymer-stabilized perfluorocarbon gas bubbles before and after their destruction with high intensity ultrasound. In addition, cryo-EM can be used to observe electron-beam induced dissipation of Nanobubble encapsulated perfluorocarbon gas.
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acoustic characterization and pharmacokinetic analyses of new Nanobubble ultrasound contrast agents
Ultrasound in Medicine and Biology, 2013Co-Authors: Nicolas Rogni, Tianyi M Krupka, Luis Solorio, Hiroki Yoshiara, Gilles Guenette, Christophe Sanders, Naohisa Kamiyama, Agata A ExneAbstract:In contrast to the clinically used microbubble ultrasound contrast agents, nanoscale bubbles (or Nanobubbles) may potentially extravasate into tumors that exhibit more permeable vasculature, facilitating targeted molecular imaging and drug delivery. Our group recently presented a simple strategy using the non-ionic surfactant Pluronic as a size control excipient to produce Nanobubbles with a mean diameter of 200 nm that exhibited stability and echogenicity on par with microbubbles. The objective of this study was to carry out an in-depth characterization of Nanobubble properties as compared with Definity microbubbles, both in vitro and in vivo. Through use of a tissue-mimicking phantom, in vitro experiments measured the echogenicity of the contrast agent solutions and the contrast agent dissolution rate over time. Nanobubbles were found to be more echogenic than Definity microbubbles at three different harmonic frequencies (8, 6.2 and 3.5 MHz). Definity microbubbles also dissolved 1.67 times faster than Nanobubbles. Pharmacokinetic studies were then performed in vivo in a subcutaneous human colorectal adenocarcinoma (LS174T) in mice. The peak enhancement and decay rates of contrast agents after bolus injection in the liver, kidney and tumor were analyzed. No significant differences were observed in peak enhancement between the Nanobubble and Definity groups in the three tested regions (tumor, liver and kidney). However, the decay rates of Nanobubbles in tumor and kidney were significantly slower than those of Definity in the first 200-s fast initial phase. There were no significant differences in the decay rates in the liver in the initial phase or in three regions of interest in the terminal phase. Our results suggest that the stability and acoustic properties of the new Nanobubble contrast agents are superior to those of the clinically used Definity microbubbles. The slower washout of Nanobubbles in tumors suggests potential entrapment of the bubbles within the tumor parenchyma.
Yuliang Wang - One of the best experts on this subject based on the ideXlab platform.
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nano wilhelmy investigation of dynamic wetting properties of afm tips through tip Nanobubble interaction
Scientific Reports, 2016Co-Authors: Yuliang Wang, Huimi Wang, Shusheng I, I GuoAbstract:The dynamic wetting properties of atomic force microscopy (AFM) tips are of much concern in many AFM-related measurement, fabrication, and manipulation applications. In this study, the wetting properties of silicon and silicon nitride AFM tips are investigated through dynamic contact angle measurement using a nano-Wilhelmy balance based method. This is done by capillary force measurement during extension and retraction motion of AFM tips relative to interfacial Nanobubbles. The working principle of the proposed method and mathematic models for dynamic contact angle measurement are presented. Geometric models of AFM tips were constructed using scanning electronic microscopy (SEM) images taken from different view directions. The detailed process of tip-Nanobubble interaction was investigated using force-distance curves of AFM on Nanobubbles. Several parameters including Nanobubble height, adhesion and capillary force between tip and Nanobubbles are extracted. The variation of these parameters was studied over Nanobubble surfaces. The dynamic contact angles of the AFM tips were calculated from the capillary force measurements. The proposed method provides direct measurement of dynamic contact angles for AFM tips and can also be taken as a general approach for nanoscale dynamic wetting property investigation.
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boundary slip and Nanobubble study in micro nanofluidics using atomic force microscopy
Soft Matter, 2010Co-Authors: Yuliang Wang, Hara HushaAbstract:The boundary condition at the solid–liquid interface on the micro/nanoscale is an important issue in micro/nanofluidic systems, where drag forces between fluids and solid walls need to be minimized. Recent studies have shown that on hydrophobic surfaces the fluid velocity near the solid surface is not equal to the velocity of the solid surface, a phenomenon called boundary slip. Theoretical and experimental studies suggest that at the solid–liquid interface, the presence of Nanobubbles is responsible for boundary slip. In this review, various techniques for boundary slip investigation are described. We focus on the research performed using contact and tapping mode atomic force microscopy methods to study boundary slip on hydrophilic, hydrophobic, and superhydrophobic surfaces. The impact of surface roughness and hydrophobicity on measured slip length is discussed. The process of how to eliminate the influences of cantilever deflection and electrostatic forces on experimental measurement is discussed. Based on Nanobubble imaging on a hydrophobic surface, the role of Nanobubbles on boundary slip is discussed. Nanobubble movement and coalescence, as well as tip–Nanobubble interactions, are discussed. The relationship between Nanobubble immobility and surface structures on hydrophobic surfaces is discussed. Finally, a method to quantitatively measure sliding force on hydrophobic surfaces using atomic force microscopy is presented, and the effect of the presence of an electric field is discussed.
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improved Nanobubble immobility induced by surface structures on hydrophobic surfaces
Langmuir, 2009Co-Authors: Yuliang Wang, Hara Husha, Xuezeng ZhaoAbstract:In fluid flow on hydrophobic surfaces, boundary slip occurs at the solid-liquid interface and Nanobubbles on the surfaces are believed to be the reason for it. Boundary slip is of practical importance in micro/nanofluidics to reduce the drag force in fluid flow. However, Nanobubbles tend to move under external disturbance. Therefore, the decreased degree of Nanobubble movement (Nanobubble immobility) is of interest. In this study, Nanobubble immobility is studied on both continuously and partially coated polystyrene films. Experimental results show improved immobility on both surfaces. The nanoindents generated by Nanobubbles after immersion in a liquid for a period of time on both films and island-like structures on the partially coated film are thought to be the reasons for improved immobility. A model is developed to reveal the role of nanoindents and island structures in the improvement of Nanobubble immobility based on contact angle hysteresis and surface tension. Analysis shows that both structures increase the initial force needed to move Nanobubbles. Hence, Nanobubble immobility is improved on both surfaces as compared with smooth hydrophobic surfaces.
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coalescence and movement of Nanobubbles studied with tapping mode afm and tip bubble interaction analysis
Journal of Physics: Condensed Matter, 2008Co-Authors: Bharat Bhushan, Yuliang Wang, Abdelhamid MaaliAbstract:Imaging of a polystyrene (PS) coated silicon wafer immersed in deionized (DI) water was conducted using atomic force microscopy (AFM) in the tapping mode (TMAFM). As reported earlier, spherical cap-like domains, referred to as Nanobubbles, were observed to be distributed on the PS surface. Experiments reveal that, in addition to the well-known parameter of scan load, scan speed is also an important parameter which affects Nanobubble coalescence. The process of Nanobubble coalescence was studied. It was found that during coalescence, small Nanobubbles were easily moved and merged into bigger ones. Based on the interaction between the AFM cantilever tip and a bubble in the so-called force modulation mode of TMAFM, bubble height and adhesive force information for a given bubble was extracted. A viscoelastic model is used to obtain the interaction stiffness and damping coefficient, which provides a method to obtain the mechanical properties of Nanobubbles. The model was further used to study the effect of surface tension force on attractive interaction force and contact angle hysteresis on the changes of the interaction damping coefficient during tip–bubble interaction.
James Richard Thorley Seddo - One of the best experts on this subject based on the ideXlab platform.
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Nanobubble nanoparticle interactions in bulk solutions
Langmuir, 2016Co-Authors: Minmi Zhang, James Richard Thorley SeddoAbstract:Nanobubbles form stable colloids in supersaturated solutions. Here we demonstrate the ability of these solutions to interact with Au nanoparticle suspensions. The principle goal was to demonstrate particle modification, similar to froth flotation, and we do indeed see bubble–particle interactions. However, unlike in froth flotation, where bubble–particle interactions are driven mainly through collisions, for bulk Nanobubble solutions we find that the principle interaction is through nucleation of new Nanobubbles on the particles.
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diffusive shielding stabilizes bulk Nanobubble clusters
ChemPhysChem, 2012Co-Authors: Joos H Weijs, James Richard Thorley Seddo, Detlef LohseAbstract:Using molecular dynamics, we study the nucleation and stability of bulk Nanobubble clusters. We study the formation, growth, and final size of bulk Nanobubbles. We find that, as long as the bubble-bubble interspacing is small enough, bulk Nanobubbles are stable against dissolution. Simple diffusion calculations provide an excellent match with the simulation results, giving insight into the reason for the stability: Nanobubbles in a cluster of bulk Nanobubbles protect each other from diffusion by a shielding effect.
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knudsen gas provides Nanobubble stability
Physical Review Letters, 2011Co-Authors: James Richard Thorley Seddo, Henricus J W Zandvlie, Detlef LohseAbstract:We provide a model for the remarkable stability of surface Nanobubbles to bulk dissolution. The key to the solution is that the gas in a Nanobubble is of Knudsen type. This leads to the generation of a bulk liquid flow which effectively forces the diffusive gas to remain local. Our model predicts the presence of a vertical water jet immediately above a Nanobubble, with an estimated speed of ∼3.3 m/s, in good agreement with our experimental atomic force microscopy measurement of ∼2.7 m/s. In addition, our model also predicts an upper bound for the size of Nanobubbles, which is consistent with the available experimental data.
Holge Schonhe - One of the best experts on this subject based on the ideXlab platform.
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surface Nanobubbles studied by time resolved fluorescence microscopy methods combined with afm the impact of surface treatment on Nanobubble nucleation
Langmuir, 2016Co-Authors: Nicole Hai, Daniel Wesne, Sergey I Druzhini, Holge SchonheAbstract:The impact of surface treatment and modification on surface Nanobubble nucleation in water has been addressed by a new combination of fluorescence lifetime imaging microscopy (FLIM) and atomic force microscopy (AFM). In this study, rhodamine 6G (Rh6G)-labeled surface Nanobubbles nucleated by the ethanol–water exchange were studied on differently cleaned borosilicate glass, silanized glass as well as self-assembled monolayers on transparent gold by combined AFM-FLIM. While the AFM data confirmed earlier reports on surface Nanobubble nucleation, size, and apparent contact angles in dependence of the underlying substrate, the colocalization of these elevated features with highly fluorescent features observed in confocal intensity images added new information. By analyzing the characteristic contributions to the excited state lifetime of Rh6G in decay curves obtained from time-correlated single photon counting (TCSPC) experiments, the characteristic short-lived (<600 ps) component of could be associated with ...
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dimensions and the profile of surface Nanobubbles tip Nanobubble interactions and Nanobubble deformation in atomic force microscopy
Langmuir, 2014Co-Authors: Wiktoria Walczyk, Holge SchonheAbstract:The interactions between argon surface Nanobubbles and AFM tips on HOPG (highly oriented pyrolitic graphite) in water and the concomitant Nanobubble deformation were analyzed as a function of position on the Nanobubbles in a combined tapping mode and force–volume mode AFM study with hydrophilic and hydrophobic AFM tips. On the basis of the detailed analysis of force–distance curves acquired on the bubbles, we found that for hydrophobic tips the bubble interface may jump toward the tip and that the tip–bubble interaction strength and the magnitude of the bubble deformation were functions of vertical and horizontal position of the tip on the bubble and depended on the bubble size and tip size and functionality. The spatial variation is attributed to long-range attractive forces originating from the substrate under the bubbles, which dominate the interaction at the bubble rim. The nonuniform bubble deformation leads to a nonuniform underestimation of the bubble height, width, and contact angle in conventiona...
