Acoustic Resonance Effects and Cavitation in SAW Aerosol Generation

The interaction of surface acoustic waves (SAWs) with liquids enables the production of aerosols with adjustable droplet sizes in the micrometer range expelled from a very compact source. Understanding the nonlinear acousto-hydrodynamics of SAWs with a regulated micro-scale liquid film is essential for acousto-microfluidics platforms, particularly aerosol generators. In this study, we demonstrate the presence of micro-cavitation in an MHz-frequency SAW aerosol generation platform, which is touted as a leap in aerosol technology with versatile application fields including biomolecule inhalation therapy, micro-chromatography and spectroscopy, olfactory displays, and material deposition. Using analysis methods with high temporal and spatial resolution, we demonstrate that SAWs stabilize spatially arranged liquid micro-domes atop the generator's surface. Our experiments show that these liquid domes become acoustic resonators with highly fluctuating pressure amplitudes that can even nucleate cavitation bubbles, as supported by analytical modeling. The observed fragmentation of liquid domes indicates the participation of three droplet generation mechanisms, including cavitation and capillary-wave instabilities. During aerosol generation, the cavitation bubbles contribute to the ejection of droplets from the liquid domes and also explain observed microstructural damage patterns on the chip surface eventually caused by cavitation-based erosion

Acoustic resonance effects and cavitation in SAW aerosol generation

The interaction of surface acoustic waves (SAWs) with liquids enables the production of aerosols with adjustable droplet sizes in the micrometer range expelled from a very compact source. Understanding the nonlinear acousto-hydrodynamics of SAWs with a regulated micro-scale liquid film is essential for acousto-microfluidics platforms, particularly aerosol generators. In this study, we demonstrate the presence of micro-cavitation in a MHz-frequency SAW aerosol generation platform, which is touted as a leap in aerosol technology with versatile application fields including biomolecule inhalation therapy, micro-chromatography and spectroscopy, olfactory displays, and material deposition. Using analysis methods with high temporal and spatial resolution, we demonstrate that SAWs stabilize spatially arranged liquid micro-domes atop the generator's surface. Our experiments show that these liquid domes become acoustic resonators with highly fluctuating pressure amplitudes that can even nucleate cavitation bubbles, as supported by analytical modeling. The observed fragmentation of liquid domes indicates the participation of three droplet generation mechanisms, including cavitation and capillary-wave instabilities. During aerosol generation, the cavitation bubbles contribute to the ejection of droplets from the liquid domes and also explain observed microstructural damage patterns on the chip surface eventually caused by cavitation-based erosion

Author Correction: Surface acoustic wave nebulization improves compound selectivity of low-temperature plasma ionization for mass spectrometry

Correction to: Scientific Reports https://doi.org/10.1038/s41598-021-82423-w, published online 03 February 202

Surface acoustic wave nebulization improves compound selectivity of low-temperature plasma ionization for mass spectrometry

Mass spectrometry coupled to low-temperature plasma ionization (LTPI) allows for immediate and easy analysis of compounds from the surface of a sample at ambient conditions. The efficiency of this process, however, strongly depends on the successful desorption of the analyte from the surface to the gas phase. Whilst conventional sample heating can improve analyte desorption, heating is not desirable with respect to the stability of thermally labile analytes. In this study using aromatic amines as model compounds, we demonstrate that (1) surface acoustic wave nebulization (SAWN) can significantly improve compound desorption for LTPI without heating the sample. Furthermore, (2) SAWN-assisted LTPI shows a response enhancement up to a factor of 8 for polar compounds such as aminophenols and phenylenediamines suggesting a paradigm shift in the ionization mechanism. Additional assets of the new technique demonstrated here are (3) a reduced analyte selectivity (the interquartile range of the response decreased by a factor of 7)—a significant benefit in non-targeted analysis of complex samples—and (4) the possibility for automated online monitoring using an autosampler. Finally, (5) the small size of the microfluidic SAWN-chip enables the implementation of the method into miniaturized, mobile LTPI probes

Evaluation of overall survival and disease-free survival of adjuvant chemotherapy and hormone therapy in patients with breast cancer

Abstract : Background: This study evaluated the effect of adjuvant chemotherapy and hormone therapy on overall survival and disease-free survival in patients with breast cancer with hormone receptor-positive, HER2-negative tumor without lymph node involvement. Methods: Breast cancer patients with hormone receptor-positive, HER2-negative, and no lymph node involvement were included in this retrospective cohort study. Patient records were used to collect data on sex, age, time of disease onset, tumor subtype, tumor size, grade, lymphovascular and perineural involvement, ki67, and treatment protocols. Patients were divided into 2 groups: Patients who received both adjuvant chemotherapy and hormonal therapy and patients who received hormonal therapy only. Disease-free survival index (DFS) and overall survival index (OS) were evaluated. Results: Sixty-seven female patients were enrolled in this study. Of them, 68.2% received both adjuvant chemotherapy and hormonal therapy and 31.6% received hormonal therapy only. During follow-up, recurrences occurred in 8 patients. The 3-year and 5-year DFS were 93.4% and 90%, respectively. The 3-year and 5-year DFS were 94% and 92%, respectively, in patients who received both adjuvant chemotherapy and hormonal therapy, and 91% and 85%, respectively, in patients who received hormonal therapy. None of the factors studied affected the 3-year and 5-year DFS. The 3-year and 5-year DFS OS were 98.6% and 96.9%, respectively CONCLUSION: Adjuvant chemotherapy in patients with breast cancer with hormone receptor-positive, HER2-negative, and no lymph node involvement compared with similar patients receiving hormone therapy alone had no significant difference in disease-free survival index and overall survival index. Keywords: breast cancer; disease-free survival index; overall survival inde

Experimental investigation of spray characteristics of prefilming airblast atomizers

Für technische Zerstäubungsprozesse wird häufig eine Flüssigkeitsmenge durch die kinetische Energie eines Hochgeschwindigkeitsgases in einem Luftstromzerstäuber in Einzeltropfen dispergiert. In einem Prefilming-Luftstromzerstäuber befindet sich die zu zerstäubende Flüssigkeit zuerst auf einer Oberfläche (Prefilming-Oberfläche) um einen dünnen Flüssigkeitsfilm zu bilden, bevor sie einem Hochgeschwindigkeitsluftstrom ausgesetzt wird. Das erste Ziel dieser Untersuchungen ist, den Zerstäubungsmechanismus der Prefilming-Zerstäuber zu verstehen und den Effekt variierender Parameter des Sprühsystems beim Zerfallsmechanismus zu ermitteln. Zerfallsregime in der Nähe des Zerstäuberauslasses wurden mittels Schattenverfahren und begleitend durch Partikelverfolgung bestimmt. Im nächsten Schritt wird die Sprühleistung des Prefilming-Luftstromzerstäubers in einer Reihe von Testbedingungen charakterisiert. Die Sprühcharakterisierung wurde mittels Phasen-Doppler-Anemometrie (PDA) durchgeführt um den Einfluss verschiedener Parameter auf die lokale Tropfengröße und Geschwindigkeit im Spray zu untersuchen. Zuletzt werden Zukunftsansätze zu Entwicklung und Design eines Prefilming-Luftstromzerstäubers aufgezeigt. Um einen einzigartigen funktionellen Zusammenhang der experimentellen Daten zu entwickeln, wurde eine Dimensionsanalyse durchgeführt. Darauffolgend zeigt der Einfluss von zwei dimensionslosen Kennzahlen unterschiedliche Sensitivitäten in Abhängigkeit vom Druckbereich und es wurde durch Anpassen der Daten eine geeigneten Korrelationsfunktion hergeteiltet.A bulk of liquid dispersed into single droplets using the kinetic energy of a high-velocity gas in an air-blast atomizer is frequently employed in technical atomization processes. In a prefilming air-blast atomizer, the atomizing liquid is primary situated on a surface (prefilming surface) to form a thin liquid film before exposing to a high-velocity air flow. The first purpose of this study is to understand atomization mechanisms close to prefilming atomizers and to determine the effect of spray system parameter variations on breakup mechanisms. Breakup regimes in the vicinity of the atomizer exit were determined using the shadowgraphy technique associated with particle tracking. In a next step, the spray performance of prefilming air-blast atomizers are characterized in a wide range of test conditions. For the spray characterization, a phase Doppler anemometry (PDA) was utilized to investigate the influence of variable parameters on the local droplet size and velocity in a spray. Finally, prediction approaches are determined for the development and design of a prefilming air-blast atomizer. In order to develop a unique functional relationship from experimental data, a dimensional analysis has been performed. Subsequently, the influence of two main nondimensional numbers shows different sensitivities depending on the pressure range and was quantified by fitting the data to appropriate correlation functions

Experimental investigation of spray characteristics of prefilming airblast atomizers

Für technische Zerstäubungsprozesse wird häufig eine Flüssigkeitsmenge durch die kinetische Energie eines Hochgeschwindigkeitsgases in einem Luftstromzerstäuber in Einzeltropfen dispergiert. In einem Prefilming-Luftstromzerstäuber befindet sich die zu zerstäubende Flüssigkeit zuerst auf einer Oberfläche (Prefilming-Oberfläche) um einen dünnen Flüssigkeitsfilm zu bilden, bevor sie einem Hochgeschwindigkeitsluftstrom ausgesetzt wird. Das erste Ziel dieser Untersuchungen ist, den Zerstäubungsmechanismus der Prefilming-Zerstäuber zu verstehen und den Effekt variierender Parameter des Sprühsystems beim Zerfallsmechanismus zu ermitteln. Zerfallsregime in der Nähe des Zerstäuberauslasses wurden mittels Schattenverfahren und begleitend durch Partikelverfolgung bestimmt. Im nächsten Schritt wird die Sprühleistung des Prefilming-Luftstromzerstäubers in einer Reihe von Testbedingungen charakterisiert. Die Sprühcharakterisierung wurde mittels Phasen-Doppler-Anemometrie (PDA) durchgeführt um den Einfluss verschiedener Parameter auf die lokale Tropfengröße und Geschwindigkeit im Spray zu untersuchen. Zuletzt werden Zukunftsansätze zu Entwicklung und Design eines Prefilming-Luftstromzerstäubers aufgezeigt. Um einen einzigartigen funktionellen Zusammenhang der experimentellen Daten zu entwickeln, wurde eine Dimensionsanalyse durchgeführt. Darauffolgend zeigt der Einfluss von zwei dimensionslosen Kennzahlen unterschiedliche Sensitivitäten in Abhängigkeit vom Druckbereich und es wurde durch Anpassen der Daten eine geeigneten Korrelationsfunktion hergeteiltet.A bulk of liquid dispersed into single droplets using the kinetic energy of a high-velocity gas in an air-blast atomizer is frequently employed in technical atomization processes. In a prefilming air-blast atomizer, the atomizing liquid is primary situated on a surface (prefilming surface) to form a thin liquid film before exposing to a high-velocity air flow. The first purpose of this study is to understand atomization mechanisms close to prefilming atomizers and to determine the effect of spray system parameter variations on breakup mechanisms. Breakup regimes in the vicinity of the atomizer exit were determined using the shadowgraphy technique associated with particle tracking. In a next step, the spray performance of prefilming air-blast atomizers are characterized in a wide range of test conditions. For the spray characterization, a phase Doppler anemometry (PDA) was utilized to investigate the influence of variable parameters on the local droplet size and velocity in a spray. Finally, prediction approaches are determined for the development and design of a prefilming air-blast atomizer. In order to develop a unique functional relationship from experimental data, a dimensional analysis has been performed. Subsequently, the influence of two main nondimensional numbers shows different sensitivities depending on the pressure range and was quantified by fitting the data to appropriate correlation functions

Experimental and Theoretical Investigation of Nucleation Site Density and Heat Transfer During Dropwise Condensation on Thin Hydrophobic Coatings

Dropwise condensation (DWC) has the potential to enhance heat transfer compared to filmwise condensation (FWC). The heat transfer rates achieved by DWC depend on the drop size distribution, which is influenced by nucleation processes of newly formed drops. In DWC modeling, the nucleation site density Ns is used as an input parameter to obtain the drop size distribution of small drops. However, due to the small scale of the condensate nuclei, direct observation is difficult, and experimental data on the nucleation site density are scarce. In the literature, values in the range of 109 m−2 to 1015 m−2 can be found for Ns. In this paper, we report DWC experiments on SiO2 and 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) thin hydrophobic coatings that show significantly different nucleation site densities. Nucleation site densities are estimated from high-speed imaging of small drops during initial condensation and from model calibration using established DWC theory. We have found the values for Ns to be in the range from 1.1×1010 m−2 to 5.1×1011 m−2 for the SiO2 coating and 1011 m−2 to 1013 m−2 for the PFDTES coating. Our results show that there can be large differences in the nucleation site density under similar conditions depending on the surface properties. This underlines the importance of investigating nucleation site density specifically for each surface and under consideration of the specific process conditions used for DWC