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Stratification in Drying Films Containing Bidisperse Mixtures of Nanoparticles

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dc.contributor.authorTang, Yanfeien
dc.contributor.authorGrest, Gary S.en
dc.contributor.authorCheng, Shengfengen
dc.contributor.departmentPhysicsen
dc.date.accessioned2019-02-04T14:18:25Zen
dc.date.available2019-02-04T14:18:25Zen
dc.date.issued2018-06-19en
dc.date.updated2019-02-04T14:18:24Zen
dc.description.abstractLarge scale molecular dynamics simulations for bidisperse nanoparticle suspensions with an explicit solvent are used to investigate the effects of evaporation rates and volume fractions on the nanoparticle distribution during drying. Our results show that "small-on-top" stratification can occur when Pe sϕ s ≳ c with c ∼ 1, where Pe s is the Péclet number and ϕ s is the volume fraction of the smaller particles. This threshold of Pe sϕ s for "small-on-top" is larger by a factor of ∼α2 than the prediction of the model treating solvent as an implicit viscous background, where α is the size ratio between the large and small particles. Our simulations further show that when the evaporation rate of the solvent is reduced, the "small-on-top" stratification can be enhanced, which is not predicted by existing theories. This unexpected behavior is explained with thermophoresis associated with a positive gradient of solvent density caused by evaporative cooling at the liquid/vapor interface. For ultrafast evaporation the gradient is large and drives the nanoparticles toward the liquid/vapor interface. This phoretic effect is stronger for larger nanoparticles, and consequently the "small-on-top" stratification becomes more distinct when the evaporation rate is slower (but not too slow such that a uniform distribution of nanoparticles in the drying film is produced), as thermophoresis that favors larger particles on the top is mitigated. A similar effect can lead to "large-on-top" stratification for Pe sϕ s above the threshold when Pe s is large but ϕ s is small. Our results reveal the importance of including the solvent explicitly when modeling evaporation-induced particle separation and organization and point to the important role of density gradients brought about by ultrafast evaporation.en
dc.description.versionPublished versionen
dc.format.extentPages 7161-7170en
dc.format.extent10 page(s)en
dc.format.mediumPrint-Electronicen
dc.identifier.doihttps://doi.org/10.1021/acs.langmuir.8b01334en
dc.identifier.eissn1520-5827en
dc.identifier.issn0743-7463en
dc.identifier.issue24en
dc.identifier.orcidCheng, Shengfeng [0000-0002-6066-2968]en
dc.identifier.pmid29792029en
dc.identifier.urihttp://hdl.handle.net/10919/87424en
dc.identifier.volume34en
dc.languageEnglishen
dc.publisherAmerican Chemical Societyen
dc.relation.urihttp://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000436022900021&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=930d57c9ac61a043676db62af60056c1en
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectScience & Technologyen
dc.subjectPhysical Sciencesen
dc.subjectTechnologyen
dc.subjectChemistry, Multidisciplinaryen
dc.subjectChemistry, Physicalen
dc.subjectMaterials Science, Multidisciplinaryen
dc.subjectChemistryen
dc.subjectMaterials Scienceen
dc.subjectSOLVENT EVAPORATIONen
dc.subjectCOLLOIDAL DISPERSIONSen
dc.subjectPOLYMER-FILMSen
dc.subjectAUTOSTRATIFICATIONen
dc.subjectPARTICLESen
dc.subjectDYNAMICSen
dc.subjectCOATINGSen
dc.subjectDRIVENen
dc.subjectMD Multidisciplinaryen
dc.subjectChemical Physicsen
dc.titleStratification in Drying Films Containing Bidisperse Mixtures of Nanoparticlesen
dc.title.serialLANGMUIRen
dc.typeArticle - Refereeden
dc.type.otherArticleen
dc.type.otherJournalen
pubs.organisational-group/Virginia Tech/Scienceen
pubs.organisational-group/Virginia Techen
pubs.organisational-group/Virginia Tech/All T&R Facultyen
pubs.organisational-group/Virginia Tech/Science/Physicsen
pubs.organisational-group/Virginia Tech/Science/COS T&R Facultyen

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