Improvement of tool reliability and uptime is a current focus in development of extreme ultraviolet lithography. The lifetime of collection mirrors for extreme ultraviolet light in tin-based plasma light sources is limited considerably by contamination with thick tin deposits that cannot be removed sufficiently fast by plasma etching. For tin droplet splats sticking to large substrates, we have developed and compared several efficient cleaning techniques based on cryogenic cooling. A silicon carbide substrate and different silicon wafer samples with up to 6 inch diameter with the surface uncoated, multilayer-coated, unstructured and grating-structured were tested. After tin dripping onto heated samples, embrittlement of droplet contamination is induced in-situ by stresses during phase transformation, following the initiation of tin pest with seed crystals of gray tin. Conversion of initially adhesive deposits to loose gray tin has been reached in less than 24 hours on all tested surfaces by continuous cooling with cold nitrogen vapor to temperatures in the range of -30 to -50 °C. Alternatively, stress-initiated tin-removal by delamination of beta-Sn droplet splats has been attained via contraction strain induced by strong cooling to temperatures of around -120 °C. Profilometry has been used to analyze the bottom side of tin droplet splats removed from a grating-structured wafer. The in-situ tin cleaning techniques give results comparable to fast ex-situ cleaning that has been achieved either by sample immersion in liquid nitrogen or by splat removal after CO2 snowflake aerosol impact using a hand-held jet-nozzle. The implementation of the in-situ phase-conversion concept for the cleaning of collector mirrors in commercial light sources for lithography is discussed.
{"title":"Cryogenic cleaning of tin-drop contamination on surfaces relevant for extreme ultraviolet light collection","authors":"N. Böwering, C. Meier","doi":"10.1116/6.0000501","DOIUrl":"https://doi.org/10.1116/6.0000501","url":null,"abstract":"Improvement of tool reliability and uptime is a current focus in development of extreme ultraviolet lithography. The lifetime of collection mirrors for extreme ultraviolet light in tin-based plasma light sources is limited considerably by contamination with thick tin deposits that cannot be removed sufficiently fast by plasma etching. For tin droplet splats sticking to large substrates, we have developed and compared several efficient cleaning techniques based on cryogenic cooling. A silicon carbide substrate and different silicon wafer samples with up to 6 inch diameter with the surface uncoated, multilayer-coated, unstructured and grating-structured were tested. After tin dripping onto heated samples, embrittlement of droplet contamination is induced in-situ by stresses during phase transformation, following the initiation of tin pest with seed crystals of gray tin. Conversion of initially adhesive deposits to loose gray tin has been reached in less than 24 hours on all tested surfaces by continuous cooling with cold nitrogen vapor to temperatures in the range of -30 to -50 °C. Alternatively, stress-initiated tin-removal by delamination of beta-Sn droplet splats has been attained via contraction strain induced by strong cooling to temperatures of around -120 °C. Profilometry has been used to analyze the bottom side of tin droplet splats removed from a grating-structured wafer. The in-situ tin cleaning techniques give results comparable to fast ex-situ cleaning that has been achieved either by sample immersion in liquid nitrogen or by splat removal after CO2 snowflake aerosol impact using a hand-held jet-nozzle. The implementation of the in-situ phase-conversion concept for the cleaning of collector mirrors in commercial light sources for lithography is discussed.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":"93 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90541124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We performed several measurements of anomalous forces on a dielectric rotor in operation, subjected to high voltage. The device operated under constant and intense angular velocity for each high voltage applied. The measurements were made in the similar way than an analogue magnetic gyroscope, by considering clockwise and counterclockwise rotations. We found that there are significant weight reduction on the device in the clockwise case, with one order of magnitude higher than the magnetic case. In addition, we detected a similar asymmetry in the observation of the effect, that is, there are smaller results for the anomalous forces in counterclockwise rotation. We also propose a theoretical model to explain the quantitative effect based on average values of macroscopic observables of the device rotation and concluded that it is consistent with the experimental results.
{"title":"Characterization of Anomalous Forces in Dielectric Rotors","authors":"E. Porcelli, V. S. Filho","doi":"10.1139/CJP-2020-0570","DOIUrl":"https://doi.org/10.1139/CJP-2020-0570","url":null,"abstract":"We performed several measurements of anomalous forces on a dielectric rotor in operation, subjected to high voltage. The device operated under constant and intense angular velocity for each high voltage applied. The measurements were made in the similar way than an analogue magnetic gyroscope, by considering clockwise and counterclockwise rotations. We found that there are significant weight reduction on the device in the clockwise case, with one order of magnitude higher than the magnetic case. In addition, we detected a similar asymmetry in the observation of the effect, that is, there are smaller results for the anomalous forces in counterclockwise rotation. We also propose a theoretical model to explain the quantitative effect based on average values of macroscopic observables of the device rotation and concluded that it is consistent with the experimental results.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":"62 7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91074418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report a decreased surface wettability when polymer films on a glass substrate are treated by ultra-fast laser pulses in a back-illumination geometry. We propose that back-illumination through the substrate confines chemical changes beneath the surface of polymer films, leaving the surface blistered but chemically intact. To confirm this hypothesis, we measure the phase contrast of the polymer when observed with a focused ion beam. We observe a void at the polymer-quartz interface that results from the expansion of an ultrafast laser-induced plasma. A modified polymer layer surrounds the void, but otherwise the film seems unmodified. We also use X-ray photoelectron spectroscopy to confirm that there is no chemical change to the surface. When patterned with partially overlapping blisters, our polymer surface shows increased hydrophobicity. The increased hydrophobicity of back-illuminated surfaces can only result from the morphological change. This contrasts with the combined chemical and morphological changes of the polymer surface caused by a front-illumination geometry.
{"title":"Surface adhesion of back-illuminated ultrafast laser-treated polymers","authors":"D. Kallepalli, Alan T. K. Godfrey, Jesse Ratté, A. Staudte, Chunmei Zhang, P. Corkum","doi":"10.1103/PhysRevMaterials.5.045201","DOIUrl":"https://doi.org/10.1103/PhysRevMaterials.5.045201","url":null,"abstract":"We report a decreased surface wettability when polymer films on a glass substrate are treated by ultra-fast laser pulses in a back-illumination geometry. We propose that back-illumination through the substrate confines chemical changes beneath the surface of polymer films, leaving the surface blistered but chemically intact. To confirm this hypothesis, we measure the phase contrast of the polymer when observed with a focused ion beam. We observe a void at the polymer-quartz interface that results from the expansion of an ultrafast laser-induced plasma. A modified polymer layer surrounds the void, but otherwise the film seems unmodified. We also use X-ray photoelectron spectroscopy to confirm that there is no chemical change to the surface. When patterned with partially overlapping blisters, our polymer surface shows increased hydrophobicity. The increased hydrophobicity of back-illuminated surfaces can only result from the morphological change. This contrasts with the combined chemical and morphological changes of the polymer surface caused by a front-illumination geometry.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":"249 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87018193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this work, we develop a numerical fitting routine to extract multiple thermal parameters using frequency-domain thermoreflectance (FDTR) for materials having non-standard, non-semi-infinite geometries. The numerical fitting routine is predicated on either a 2-D or 3-D finite element analysis that permits the inclusion of non semi-infinite boundary conditions, which can not be considered in the analytical solution to the heat diffusion equation in the frequency domain. We validate the fitting routine by comparing it to the analytical solution to the heat diffusion equation used within the wider literature for FDTR and known values of thermal conductivity for semi-infinite substrates (SiO2, Al2O3 and Si). We then demonstrate its capacity to extract the thermal properties of Si when etched into micropillars that have radii on the order of the pump beam. Experimental measurements of Si micropillars with circular cross-sections are provided and fit using the numerical fitting routine established as part of this work. Likewise, we show that the analytical solution is unsuitable for the extraction of thermal properties when the geometry deviates significantly from the standard semi-infinite case. This work is critical for measuring the thermal properties of materials having arbitrary geometries, including ultra-drawn glass fibers and laser gain media.
{"title":"A numerical fitting routine for frequency-domain thermoreflectance measurements of nanoscale material systems having arbitrary geometries","authors":"R. Warzoha, Adam A. Wilson, Brian F. Donovan, A. Smith, N. Vu, Trent Perry, Longnan Li, N. Miljkovic, E. Getto","doi":"10.1063/5.0030168","DOIUrl":"https://doi.org/10.1063/5.0030168","url":null,"abstract":"In this work, we develop a numerical fitting routine to extract multiple thermal parameters using frequency-domain thermoreflectance (FDTR) for materials having non-standard, non-semi-infinite geometries. The numerical fitting routine is predicated on either a 2-D or 3-D finite element analysis that permits the inclusion of non semi-infinite boundary conditions, which can not be considered in the analytical solution to the heat diffusion equation in the frequency domain. We validate the fitting routine by comparing it to the analytical solution to the heat diffusion equation used within the wider literature for FDTR and known values of thermal conductivity for semi-infinite substrates (SiO2, Al2O3 and Si). We then demonstrate its capacity to extract the thermal properties of Si when etched into micropillars that have radii on the order of the pump beam. Experimental measurements of Si micropillars with circular cross-sections are provided and fit using the numerical fitting routine established as part of this work. Likewise, we show that the analytical solution is unsuitable for the extraction of thermal properties when the geometry deviates significantly from the standard semi-infinite case. This work is critical for measuring the thermal properties of materials having arbitrary geometries, including ultra-drawn glass fibers and laser gain media.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":"42 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86549803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Shape-shifting panel from 3D printed undulated ribbon lattice","authors":"Filippo Agnelli, M. Tricarico, A. Constantinescu","doi":"10.1016/J.EML.2020.101089","DOIUrl":"https://doi.org/10.1016/J.EML.2020.101089","url":null,"abstract":"","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74872352","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The rapid growth of electronic waste must be curtailed to prevent accumulation of environmentally and biologically toxic materials, which are essential to traditional electronics1. The recent proliferation of transient electronics has focused predominantly on biocompatibility(2,3), and studies reporting material recapture have only demonstrated reuse of conducting materials(4–6). Meanwhile, the ideal solution to the electronic waste epidemic — recapture and reuse of all materials — has been largely neglected. Here we show complete recyclability of all materials in printed, all-carbon electronics using paper substrates, semiconducting carbon nanotubes, conducting graphene, and insulating crystalline nanocellulose. The addition of mobile ions to the dielectric produced significant improvements in switching speed, subthreshold swing, and among the highest on-current for printed transistors. These devices evinced superlative stability over 6 months, after which they are shown to be controllably decomposed for complete recycling of materials and re-printing of devices with similar performance to baseline devices. The printing of all-carbon, recyclable electronics presents a new path toward green electronics with potential to mitigate the environmental impact of electronic waste. We anticipate all-carbon, recyclable electronics to be a watershed, facilitating internet-of-everything applications, such as ubiquitous sensors for continuous monitoring of diseases or environmental conditions, while preserving carbon neutrality in the device lifecycle.
{"title":"Fully printed, all-carbon, recyclable electronics","authors":"Nicholas X. Williams, George Bullard, N. Brooke, M. Therien, A. Franklin","doi":"10.21203/rs.3.rs-74355/v1","DOIUrl":"https://doi.org/10.21203/rs.3.rs-74355/v1","url":null,"abstract":"\u0000 The rapid growth of electronic waste must be curtailed to prevent accumulation of environmentally and biologically toxic materials, which are essential to traditional electronics1. The recent proliferation of transient electronics has focused predominantly on biocompatibility(2,3), and studies reporting material recapture have only demonstrated reuse of conducting materials(4–6). Meanwhile, the ideal solution to the electronic waste epidemic — recapture and reuse of all materials — has been largely neglected. Here we show complete recyclability of all materials in printed, all-carbon electronics using paper substrates, semiconducting carbon nanotubes, conducting graphene, and insulating crystalline nanocellulose. The addition of mobile ions to the dielectric produced significant improvements in switching speed, subthreshold swing, and among the highest on-current for printed transistors. These devices evinced superlative stability over 6 months, after which they are shown to be controllably decomposed for complete recycling of materials and re-printing of devices with similar performance to baseline devices. The printing of all-carbon, recyclable electronics presents a new path toward green electronics with potential to mitigate the environmental impact of electronic waste. We anticipate all-carbon, recyclable electronics to be a watershed, facilitating internet-of-everything applications, such as ubiquitous sensors for continuous monitoring of diseases or environmental conditions, while preserving carbon neutrality in the device lifecycle.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78855650","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This note presents a comprehensive characterization of physical and mechanical properties of water repellent (hydrophobic) soil collected from Cleveland National Forest in California immediately after the Holy Fire, 2018, and delineates comparisons with chemically induced hydrophobic sand in the laboratory. Hydrophobicity is a particle surface characteristic that governs different levels of attraction between water molecules and solid particles. Wildfires can cause different levels of hydrophobicity in shallow soil layers based on fire severity, vegetation, and chemical structure of the soil. Natural and chemically induced regular and hydrophobic sands are characterized by grain size distribution, water retention curve, water contact angle and electron microscopic imaging, including the relationship between water entry value and the drop contact angle in hydrophobic soil. Comparative knowledge of natural and chemically induced hydrophobic soil properties will help future research to better predict soil behavior and improve insights into post-wildfire soil erosion and mudflow mechanisms. This note contributes to a database of wildfire-induced hydrophobic soil with detailed properties and assesses the applicability of laboratory made hydrophobic soils for studying mudflows by comparison to the natural water repellent soil collected from the burned site.
{"title":"Assessment of Physical Properties of Water Repellent Soils","authors":"M. Movasat, I. Tomac","doi":"10.1061/(ASCE)GT.1943-5606.0002604","DOIUrl":"https://doi.org/10.1061/(ASCE)GT.1943-5606.0002604","url":null,"abstract":"This note presents a comprehensive characterization of physical and mechanical properties of water repellent (hydrophobic) soil collected from Cleveland National Forest in California immediately after the Holy Fire, 2018, and delineates comparisons with chemically induced hydrophobic sand in the laboratory. Hydrophobicity is a particle surface characteristic that governs different levels of attraction between water molecules and solid particles. Wildfires can cause different levels of hydrophobicity in shallow soil layers based on fire severity, vegetation, and chemical structure of the soil. Natural and chemically induced regular and hydrophobic sands are characterized by grain size distribution, water retention curve, water contact angle and electron microscopic imaging, including the relationship between water entry value and the drop contact angle in hydrophobic soil. Comparative knowledge of natural and chemically induced hydrophobic soil properties will help future research to better predict soil behavior and improve insights into post-wildfire soil erosion and mudflow mechanisms. This note contributes to a database of wildfire-induced hydrophobic soil with detailed properties and assesses the applicability of laboratory made hydrophobic soils for studying mudflows by comparison to the natural water repellent soil collected from the burned site.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81544898","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ising machines based on analog systems have the potential of acceleration in solving ubiquitous combinatorial optimization problems. Although some artificial spins to support large-scale Ising machine is reported, e.g. superconducting qubits in quantum annealers and short optical pulses in coherent Ising machines, the spin coherence is fragile due to the ultra-low equivalent temperature or optical phase sensitivity. In this paper, we propose to use short microwave pulses generated from an optoelectronic parametric oscillator as the spins to implement the Ising machine with large scale and also high coherence under room temperature. The proposed machine supports 10,000 spins, and the high coherence leads to accurate computation. Moreover, the Ising machine is highly compatible with high-speed electronic devices for programmability, paving a low-cost, accurate, and easy-to-implement way toward to solve real-world optimization problems.
{"title":"Microwave Photonic Ising Machine","authors":"Qizhuang Cen, Tengfei Hao, Hao Ding, Shanhong Guan, Zhiqiang Qin, Kun Xu, Yitang Dai, Ming Li","doi":"10.21203/rs.3.rs-79539/v1","DOIUrl":"https://doi.org/10.21203/rs.3.rs-79539/v1","url":null,"abstract":"\u0000 Ising machines based on analog systems have the potential of acceleration in solving ubiquitous combinatorial optimization problems. Although some artificial spins to support large-scale Ising machine is reported, e.g. superconducting qubits in quantum annealers and short optical pulses in coherent Ising machines, the spin coherence is fragile due to the ultra-low equivalent temperature or optical phase sensitivity. In this paper, we propose to use short microwave pulses generated from an optoelectronic parametric oscillator as the spins to implement the Ising machine with large scale and also high coherence under room temperature. The proposed machine supports 10,000 spins, and the high coherence leads to accurate computation. Moreover, the Ising machine is highly compatible with high-speed electronic devices for programmability, paving a low-cost, accurate, and easy-to-implement way toward to solve real-world optimization problems.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":"79 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89015494","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We use micro-focussed Brillouin light scattering spectroscopy ($mu$BLS) to investigate surface acoustic waves (SAWs) in a GaN layer on a Si substrate at GHz frequencies. Furthermore, we discuss the concept of $mu$BLS for SAWs and show that the crucial parameters of SAW excitation and propagation can be measured. We investigate a broad range of excitation parameters and observe that Rayleigh and Sezawa waves are excited simultaneously at the same frequency. Spatially resolved measurements of these co-propagating waves show a periodic pattern, which proves their coherent interference. From the periodicity of the spatial phonon patterns, the wavevector difference between the two waves has been identified and compared to the dispersion relation. This concept of co-propagating phonons might be used to produce acoustic or magneto-elastic fields with a time-independent spatial variation similar to the situations realized using counter-propagating waves. However, co-propagating SAW have a well defined direction of the wave vector and thus, posses a finite phonon angular momentum which offers new opportunities, e.g. for angular momentum conversion experiments.
{"title":"Interference of co-propagating Rayleigh and Sezawa waves observed with micro-focused Brillouin light scattering spectroscopy","authors":"M. Geilen, F. Kohl, A. Nicoloiu, A. Müller, B. Hillebrands, P. Pirro","doi":"10.1063/5.0029308","DOIUrl":"https://doi.org/10.1063/5.0029308","url":null,"abstract":"We use micro-focussed Brillouin light scattering spectroscopy ($mu$BLS) to investigate surface acoustic waves (SAWs) in a GaN layer on a Si substrate at GHz frequencies. Furthermore, we discuss the concept of $mu$BLS for SAWs and show that the crucial parameters of SAW excitation and propagation can be measured. We investigate a broad range of excitation parameters and observe that Rayleigh and Sezawa waves are excited simultaneously at the same frequency. Spatially resolved measurements of these co-propagating waves show a periodic pattern, which proves their coherent interference. From the periodicity of the spatial phonon patterns, the wavevector difference between the two waves has been identified and compared to the dispersion relation. This concept of co-propagating phonons might be used to produce acoustic or magneto-elastic fields with a time-independent spatial variation similar to the situations realized using counter-propagating waves. However, co-propagating SAW have a well defined direction of the wave vector and thus, posses a finite phonon angular momentum which offers new opportunities, e.g. for angular momentum conversion experiments.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87476910","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
By now it is well-understood that the usage of facemasks provides protection from transmission of viral loads through exhalation and inhalation of respiratory droplets. Therefore, during the current Covid-19 pandemic the usage of face masks is strongly recommended by health officials. Although three-layer masks are generally advised for usage, many commonly available or homemade masks contain only single and double layers. In this study, we show through detailed physics based analyses and high speed imaging that high momentum cough droplets on impingement on single- and double-layer masks can lead to significant partial penetration and more importantly atomization into numerous much smaller daughter droplets, thereby increasing the total population of the aerosol, which can remain suspended for a longer time. The possibility of secondary atomization of high momentum cough droplets due to impingement, hydrodynamic focusing and extrusion through the microscale pores in the fibrous network of the mask has not been explored before. However, this unique mode of aerosol generation poses a finite risk of infection as shown in this work. We also demonstrate that in single layer masks close to 70 % of a given droplet volume is atomized and only 30 % is trapped within the fibers. The entrapped volume is close to 90 % for double layer masks which still allows some atomization into smaller droplets. We however found that a triple-layer surgical mask permits negligible penetration and hence should be effective in preventing disease transmission.
{"title":"Video: ON SECONDARY ATOMIZATION AND BLOCKAGE OF SURROGATE COUGH DROPLETS IN SINGLE AND MULTI-LAYER FACE MASKS","authors":"Shubham Sharma, Roven Pinto, A. Saha, Swetaprovo Chaudhuri, S. Basu","doi":"10.1103/aps.dfd.2020.gfm.v0059","DOIUrl":"https://doi.org/10.1103/aps.dfd.2020.gfm.v0059","url":null,"abstract":"By now it is well-understood that the usage of facemasks provides protection from transmission of viral loads through exhalation and inhalation of respiratory droplets. Therefore, during the current Covid-19 pandemic the usage of face masks is strongly recommended by health officials. Although three-layer masks are generally advised for usage, many commonly available or homemade masks contain only single and double layers. In this study, we show through detailed physics based analyses and high speed imaging that high momentum cough droplets on impingement on single- and double-layer masks can lead to significant partial penetration and more importantly atomization into numerous much smaller daughter droplets, thereby increasing the total population of the aerosol, which can remain suspended for a longer time. The possibility of secondary atomization of high momentum cough droplets due to impingement, hydrodynamic focusing and extrusion through the microscale pores in the fibrous network of the mask has not been explored before. However, this unique mode of aerosol generation poses a finite risk of infection as shown in this work. We also demonstrate that in single layer masks close to 70 % of a given droplet volume is atomized and only 30 % is trapped within the fibers. The entrapped volume is close to 90 % for double layer masks which still allows some atomization into smaller droplets. We however found that a triple-layer surgical mask permits negligible penetration and hence should be effective in preventing disease transmission.","PeriodicalId":8423,"journal":{"name":"arXiv: Applied Physics","volume":"51 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90610709","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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