Mettin, Robert

[["dc.bibliographiccitation.firstpage","4100"],["dc.bibliographiccitation.issue","7"],["dc.bibliographiccitation.journal","ACS Applied Materials & Interfaces"],["dc.bibliographiccitation.lastpage","4108"],["dc.bibliographiccitation.volume","7"],["dc.contributor.author","Belova-Magri, Valentina"],["dc.contributor.author","Brotchie, Adam"],["dc.contributor.author","Cairos, Carlos"],["dc.contributor.author","Mettin, Robert"],["dc.contributor.author","Mohwald, Helmuth"],["dc.date.accessioned","2018-11-07T10:00:48Z"],["dc.date.available","2018-11-07T10:00:48Z"],["dc.date.issued","2015"],["dc.description.abstract","For the first time, we apply a high-speed imaging technique to record the activity of acoustically driven cavitation bubbles (86 kHz) on micropatterned surfaces with hydrophobic and hydrophilic stripes. The width of the hydrophobic stripes lies between 3.5 and 115 mu m. This work provides the first direct visualization of the preferential location of bubbles on the hydrophobic areas of the patterns. The results confirm our previous prediction that surface cavitation strongly depends on the surface energy of the irradiated substrate. The observations show a remarkable effect of the stripe width on the size, movement, growth, splitting, and multiplying of the bubbles. The high-speed imaging also reveals that there is a minimal width of the hydrophobic stripes that allows bubble attraction and formation. Our observations are supported by a theoretical approach based on the forces acting on the bubbles."],["dc.identifier.doi","10.1021/am508062h"],["dc.identifier.isi","000350193000028"],["dc.identifier.pmid","25621714"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/37885"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Chemical Soc"],["dc.relation.issn","1944-8244"],["dc.title","Micropatterning for the Control of Surface Cavitation: Visualization through High-Speed Imaging"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","170"],["dc.bibliographiccitation.journal","Ultrasonics Sonochemistry"],["dc.bibliographiccitation.lastpage","181"],["dc.bibliographiccitation.volume","33"],["dc.contributor.author","Reuter, Fabian"],["dc.contributor.author","Cairos, Carlos"],["dc.contributor.author","Mettin, Robert"],["dc.date.accessioned","2018-11-07T10:06:50Z"],["dc.date.available","2018-11-07T10:06:50Z"],["dc.date.issued","2016"],["dc.description.abstract","Cavitation bubbles collapsing in the vicinity to a solid substrate induce intense micro-convection at the solid. Here we study the transient near-wall flows generated by single collapsing bubbles by chronoamperometric measurements synchronously coupled with high-speed imaging. The individual bubbles are created at confined positions by a focused laser pulse. They reach a maximum expansion radius of approximately 425 pm. Several stand-off distances to the flat solid boundary are investigated and all distances are chosen sufficiently large that no gas phase of the expanding and collapsing bubble touches the solid directly. With a microelectrode embedded into the substrate, the time-resolved perturbations in the liquid shear layer are probed by means of a chronoamperometric technique. The measurements of electric current are synchronized with high-speed imaging of the bubble dynamics. The perturbations of the near-wall layer are found to result mainly from ring vortices created by the jetting bubble. Other bubble induced flows, such as the jet and flows following the radial bubble oscillations are perceptible with this technique, but show a minor influence at the stand-off distances investigated. (C) 2016 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.ultsonch.2016.04.023"],["dc.identifier.isi","000378956700019"],["dc.identifier.pmid","27245968"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/39171"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","1873-2828"],["dc.relation.issn","1350-4177"],["dc.title","Vortex dynamics of collapsing bubbles: Impact on the boundary layer measured by chronoamperometry"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","N3069"],["dc.bibliographiccitation.issue","1"],["dc.bibliographiccitation.journal","ECS Journal of Solid State Science and Technology"],["dc.bibliographiccitation.lastpage","N3080"],["dc.bibliographiccitation.volume","3"],["dc.contributor.author","Okorn-Schmidt, Harald F."],["dc.contributor.author","Holsteyns, Frank"],["dc.contributor.author","Lippert, Alexander"],["dc.contributor.author","Mui, David"],["dc.contributor.author","Kawaguchi, Mark"],["dc.contributor.author","Lechner, Christiane"],["dc.contributor.author","Frommhold, Philipp Erhard"],["dc.contributor.author","Nowak, Till"],["dc.contributor.author","Reuter, Fabian"],["dc.contributor.author","Pique, Miquel Banchs"],["dc.contributor.author","Cairos, Carlos"],["dc.contributor.author","Mettind, Robert"],["dc.date.accessioned","2018-11-07T09:46:36Z"],["dc.date.available","2018-11-07T09:46:36Z"],["dc.date.issued","2014"],["dc.description.abstract","Dealing with nanometer-sized particulate contamination is still one of the major challenges during the manufacturing of yielding semiconductor devices. This is especially true for the increasing number of critical processing steps, where residues of particulate matter need to be removed without mechanically damaging sensitive device patterns and, at the same time, achieve the lowest possible substrate loss. If higher substrate loss would be permitted, a more or less pure chemical mechanism could be employed (e.g. particle undercut by substrate etching and lift-off). However, being only allowed to have statistically seen sub-Angstrom material loss, physical forces need to be integrated jointly with the appropriate chemical support. In this paper we describe particle cleaning techniques, which are based on monodisperse droplet impact, controlled bubble cavitation (acoustic and laser induced), moving contact lines as well as normal-directed extensional flow to meet present and future industry requirements. (C) 2013 The Electrochemical Society. All rights reserved."],["dc.identifier.doi","10.1149/2.011401jss"],["dc.identifier.isi","000331169400012"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/34911"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Electrochemical Soc Inc"],["dc.relation.issn","2162-8769"],["dc.title","Particle Cleaning Technologies to Meet Advanced Semiconductor Device Process Requirements"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","663"],["dc.bibliographiccitation.journal","Ultrasonics Sonochemistry"],["dc.bibliographiccitation.lastpage","676"],["dc.bibliographiccitation.volume","34"],["dc.contributor.author","Thiemann, Andrea"],["dc.contributor.author","Holsteyns, Frank"],["dc.contributor.author","Cairos, Carlos"],["dc.contributor.author","Mettin, Robert"],["dc.date.accessioned","2018-11-07T10:29:39Z"],["dc.date.available","2018-11-07T10:29:39Z"],["dc.date.issued","2017"],["dc.description.abstract","The detailed link of liquid phase sonochemical reactions and bubble dynamics is still not sufficiently known. To further clarify this issue, we image sonoluminescence and bubble oscillations, translations, and shapes in an acoustic cavitation setup at 23 kHz in sulfuric acid with dissolved sodium sulfate and xenon gas saturation. The colour of sonoluminescence varies in a way that emissions from excited non-volatile sodium atoms are prominently observed far from the acoustic horn emitter (\"red region\"), while such emissions are nearly absent close to the horn tip (\"blue region\"). High-speed images reveal the dynamics of distinct bubble populations that can partly be linked to the different emission regions. In particular, we see smaller strongly collapsing spherical bubbles within the blue region, while larger bubbles with a liquid jet during collapse dominate the red region. The jetting is induced by the fast bubble translation, which is a consequence of acoustic (Bjerknes) forces in the ultrasonic field. Numerical simulations with a spherical single bubble model reproduce quantitatively the volume oscillations and fast translation of the sodium emitting bubbles. Additionally, their intermittent stopping is explained by multistability in a hysteretic parameter range. The findings confirm the assumption that bubble deformations are responsible for pronounced sodium sonoluminescence. Notably the observed translation induced jetting appears to serve as efficient mixing mechanism of liquid into the heated gas phase of collapsing bubbles, thus potentially promoting liquid phase sonochemistry in general. (C) 2016 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.ultsonch.2016.06.013"],["dc.identifier.isi","000387626500075"],["dc.identifier.pmid","27773293"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/43681"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","1873-2828"],["dc.relation.issn","1350-4177"],["dc.title","Sonoluminescence and dynamics of cavitation bubble populations in sulfuric acid"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.artnumber","023304"],["dc.bibliographiccitation.issue","2"],["dc.bibliographiccitation.journal","Physics of Fluids"],["dc.bibliographiccitation.volume","26"],["dc.contributor.author","Znidarcic, Anton"],["dc.contributor.author","Mettin, Robert"],["dc.contributor.author","Cairos, Carlos"],["dc.contributor.author","Dular, Matevz"],["dc.date.accessioned","2018-11-07T09:44:14Z"],["dc.date.available","2018-11-07T09:44:14Z"],["dc.date.issued","2014"],["dc.description.abstract","Ultrasonic horn transducers are frequently used in applications of acoustic cavitation in liquids, for instance, for cell disruption or sonochemical reactions. They are operated typically in the frequency range up to about 50 kHz and have tip diameters from some mm to several cm. It has been observed that if the horn tip is sufficiently small and driven at high amplitude, cavitation is very strong, and the tip can be covered entirely by the gas/vapor phase for longer time intervals. A peculiar dynamics of the attached cavity can emerge with expansion and collapse at a self-generated frequency in the subharmonic range, i.e., below the acoustic driving frequency. Here, we present a systematic study of the cavitation dynamics in water at a 20 kHz horn tip of 3 mm diameter. The system was investigated by high-speed imaging with simultaneous recording of the acoustic emissions. Measurements were performed under variation of acoustic power, air saturation, viscosity, surface tension, and temperature of the liquid. Our findings show that the liquid properties play no significant role in the dynamics of the attached cavitation at the small ultrasonic horn. Also the variation of the experimental geometry, within a certain range, did not change the dynamics. We believe that the main two reasons for the peculiar dynamics of cavitation on a small ultrasonic horn are the higher energy density on a small tip and the inability of the big tip to \"wash\" away the gaseous bubbles. Calculation of the somewhat adapted Strouhal number revealed that, similar to the hydrodynamic cavitation, values which are relatively low characterize slow cavitation structure dynamics. In cases where the cavitation follows the driving frequency this value lies much higher-probably at Str>20. In the spirit to distinguish the observed phenomenon with other cavitation dynamics at ultrasonic transducer surfaces, we suggest to term the observed phenomenon of attached cavities partly covering the full horn tip as \"acoustic supercavitation.\" This reflects the conjecture that not the sound field in terms of acoustic (negative) pressure in the liquid is responsible for nucleation, but the motion of the transducer surface. (C) 2014 AIP Publishing LLC."],["dc.identifier.doi","10.1063/1.4866270"],["dc.identifier.isi","000332322000017"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/34350"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Amer Inst Physics"],["dc.relation.issn","1089-7666"],["dc.relation.issn","1070-6631"],["dc.title","Attached cavitation at a small diameter ultrasonic horn tip"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","474"],["dc.bibliographiccitation.journal","Ultrasonics Sonochemistry"],["dc.bibliographiccitation.lastpage","483"],["dc.bibliographiccitation.volume","34"],["dc.contributor.author","Kauer, Markus"],["dc.contributor.author","Belova-Magri, Valentina"],["dc.contributor.author","Cairos, Carlos"],["dc.contributor.author","Schreier, Hans-Juergen"],["dc.contributor.author","Mettin, Robert"],["dc.date.accessioned","2018-11-07T10:29:39Z"],["dc.date.available","2018-11-07T10:29:39Z"],["dc.date.issued","2017"],["dc.description.abstract","Despite the increasing use of high frequency ultrasound in heterogeneous reactions, knowledge about the spatial distribution of cavitation bubbles at the irradiated solid surface is still lacking. This gap hinders controllable surface sonoreactions. Here we present an optimization study of the cavitation bubble distribution at a solid sample using sonoluminescence and sonochemiluminescence imaging. The experiments were performed at three ultrasound frequencies, namely 580, 860 and 1142 kHz. We found that position and orientation of the sample to the transducer, as, well as its material properties influence the distribution of active cavitation bubbles at the sample surface in the reactor. The reason is a significant modification of the acoustic field due to reflections and absorption of the ultrasonic wave by the solid. This is retraced by numerical simulations employing the Finite Element Method, yielding reasonable agreement of luminescent zones and high acoustic pressure amplitudes in 2D simulations. A homogeneous coverage of the test sample surface with cavitation is finally reached at nearly vertical inclination with respect to the incident wave. (C) 2016 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.ultsonch.2016.06.008"],["dc.identifier.isi","000387626500055"],["dc.identifier.pmid","27773271"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/43680"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","PUB_WoS_Import"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","1873-2828"],["dc.relation.issn","1350-4177"],["dc.title","Visualization and optimization of cavitation activity at a solid surface in high frequency ultrasound fields"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","2044"],["dc.bibliographiccitation.issue","6"],["dc.bibliographiccitation.journal","Ultrasonics Sonochemistry"],["dc.bibliographiccitation.lastpage","2051"],["dc.bibliographiccitation.volume","21"],["dc.contributor.author","Cairos, Carlos"],["dc.contributor.author","Schneider, Julia"],["dc.contributor.author","Pflieger, Rachel"],["dc.contributor.author","Mettin, Robert"],["dc.date.accessioned","2018-11-07T09:33:23Z"],["dc.date.available","2018-11-07T09:33:23Z"],["dc.date.issued","2014"],["dc.description.abstract","The sonoluminescence spectra from acoustic cavitation in aqueous NaCl solutions are systematically studied in a large range of ultrasonic frequencies under variation of electrical power and argon sparging. At the same time, bubble dynamics are analysed by high-speed imaging. Sodium line and continuum emission are evaluated for acoustic driving at 34.5, 90, 150, 365, and 945 kHz in the same reactor vessel. The results show that the ratio of sodium line to continuum emission can be shifted by the experimental parameters: an increase in the argon flow increases the ratio, while an increase in power leads to a decrease. At 945 kHz, the sodium line is drastically reduced, while the continuum stays at elevated level. Bubble observations reveal a remarkable effect of argon in terms of bubble distribution and stability: larger bubbles of non-spherical shapes form and eject small daughter bubbles which in turn populate the whole liquid. As a consequence, the bubble interactions (splitting, merging) appear enhanced which supports a link between non-spherical bubble dynamics and sodium line emission. (C) 2014 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.ultsonch.2014.03.006"],["dc.identifier.isi","000340020500022"],["dc.identifier.pmid","24690298"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/31951"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.relation.issn","1873-2828"],["dc.relation.issn","1350-4177"],["dc.title","Effects of argon sparging rate, ultrasonic power, and frequency on multibubble sonoluminescence spectra and bubble dynamics in NaCl aqueous solutions"],["dc.type","journal_article"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]

[["dc.bibliographiccitation.firstpage","24"],["dc.bibliographiccitation.journal","Ultrasonics Sonochemistry"],["dc.bibliographiccitation.lastpage","30"],["dc.bibliographiccitation.volume","25"],["dc.contributor.author","Mettin, Robert"],["dc.contributor.author","Cairos, Carlos"],["dc.contributor.author","Troia, Adriano"],["dc.date.accessioned","2018-11-07T09:55:38Z"],["dc.date.available","2018-11-07T09:55:38Z"],["dc.date.issued","2015"],["dc.description.abstract","The details of bubble behaviour in chemically active cavitation are still not sufficiently well understood. Here we report on experimental high-speed observations of acoustically driven single-bubble and few-bubble systems with the aim of clarification of the connection of their dynamics with chemical activity. Our experiment realises the sonochemical isomerization reaction of maleic acid to fumaric acid, mediated by bromine radicals, in a bubble trap set-up. The main result is that the reaction product can only be observed in a parameter regime where a small bubble cluster occurs, while a single trapped bubble stays passive. Evaluations of individual bubble dynamics for both cases are given in form of radius-time data and numerical fits to a bubble model. A conclusion is that a sufficiently strong collapse has to be accompanied by non-spherical bubble dynamics for the reaction to occur, and that the reason appears to be an efficient mixing of liquid and gas phase. This finding corroborates previous observations and literature reports on high liquid phase sonochemical activity under distinct parameter conditions than strong sonoluminescence emissions. (C) 2014 Elsevier B.V. All rights reserved."],["dc.identifier.doi","10.1016/j.ultsonch.2014.08.015"],["dc.identifier.isi","000353005200005"],["dc.identifier.pmid","25194210"],["dc.identifier.uri","https://resolver.sub.uni-goettingen.de/purl?gro-2/36796"],["dc.notes.status","zu prüfen"],["dc.notes.submitter","Najko"],["dc.publisher","Elsevier Science Bv"],["dc.publisher.place","Amsterdam"],["dc.relation.conference","14th Meeting of the European Society of Sonochemistry"],["dc.relation.eventlocation","Avignon Univ, Avignon, FRANCE"],["dc.relation.issn","1873-2828"],["dc.relation.issn","1350-4177"],["dc.title","Sonochemistry and bubble dynamics"],["dc.type","conference_paper"],["dc.type.internalPublication","yes"],["dc.type.peerReviewed","yes"],["dc.type.status","published"],["dspace.entity.type","Publication"]]