Time-Dependent Wetting Behavior of PDMS Surfaces with Bio-Inspired, Hierarchical Structures

Handle URI:
http://hdl.handle.net/10754/592756
Title:
Time-Dependent Wetting Behavior of PDMS Surfaces with Bio-Inspired, Hierarchical Structures
Authors:
Mishra, Himanshu ( 0000-0001-8759-7812 ) ; Schrader, Alex M.; Lee, Dong Woog; Gallo, Adair; Chen, Szu-Ying; Kaufman, Yair; Das, Saurabh; Israelachvili, Jacob N.
Abstract:
Wetting of rough surfaces involves time-dependent effects, such as surface deformations, non-uniform filling of surface pores within or outside the contact area, and surface chemistries, but the detailed impact of these phenomena on wetting is not entirely clear. Understanding these effects is crucial for designing coatings for a wide range of applications, such as membrane-based oil-water separation and desalination, waterproof linings/windows for automobiles, aircrafts, and naval vessels, and antibiofouling. Herein, we report on time-dependent contact angles of water droplets on a rough polydimethylsiloxane (PDMS) surface that cannot be completely described by the conventional Cassie-Baxter or Wenzel models or the recently proposed Cassie-impregnated model. Shells of sand dollars (Dendraster excentricus) were used as lithography-free, robust templates to produce rough PDMS surfaces with hierarchical, periodic features ranging from 10-7-10-4 m. Under saturated vapor conditions, we found that in the short-term (<1 min), the contact angle of a sessile water droplet on the templated PDMS, θSDT = 140° ± 3°, was accurately described by the Cassie-Baxter model (predicted θSDT = 137°); however, after 90 min, θSDT fell to 110°. Fluorescent confocal microscopy confirmed that the initial reduction in θSDT to 110° (the Wenzel limit) was primarily a Cassie-Baxter to Wenzel transition during which pores within the contact area filled gradually, and more rapidly for ethanol-water mixtures. After 90 min, the contact line of the water droplet became pinned, perhaps caused by viscoelastic deformation of the PDMS around the contact line, and a significant volume of water began to flow from the droplet to pores outside the contact region, causing θSDT to decrease to 65° over 48 h on the rough surface. The system we present here to explore the concept of contact angle time dependence (dynamics) and modeling of natural surfaces provides insights into the design and development of long- and short-lived coatings.
KAUST Department:
Water Desalination and Reuse Research Center (WDRC); Biological and Environmental Sciences and Engineering (BESE) Division
Citation:
Time-Dependent Wetting Behavior of PDMS Surfaces with Bio-Inspired, Hierarchical Structures 2015 ACS Applied Materials & Interfaces
Publisher:
American Chemical Society (ACS)
Journal:
ACS Applied Materials & Interfaces
Issue Date:
28-Dec-2015
DOI:
10.1021/acsami.5b10721
Type:
Article
ISSN:
1944-8244; 1944-8252
Additional Links:
http://pubs.acs.org/doi/10.1021/acsami.5b10721
Appears in Collections:
Articles; Water Desalination and Reuse Research Center (WDRC); Biological and Environmental Sciences and Engineering (BESE) Division

Full metadata record

DC FieldValue Language
dc.contributor.authorMishra, Himanshuen
dc.contributor.authorSchrader, Alex M.en
dc.contributor.authorLee, Dong Woogen
dc.contributor.authorGallo, Adairen
dc.contributor.authorChen, Szu-Yingen
dc.contributor.authorKaufman, Yairen
dc.contributor.authorDas, Saurabhen
dc.contributor.authorIsraelachvili, Jacob N.en
dc.date.accessioned2016-01-04T06:08:56Zen
dc.date.available2016-01-04T06:08:56Zen
dc.date.issued2015-12-28en
dc.identifier.citationTime-Dependent Wetting Behavior of PDMS Surfaces with Bio-Inspired, Hierarchical Structures 2015 ACS Applied Materials & Interfacesen
dc.identifier.issn1944-8244en
dc.identifier.issn1944-8252en
dc.identifier.doi10.1021/acsami.5b10721en
dc.identifier.urihttp://hdl.handle.net/10754/592756en
dc.description.abstractWetting of rough surfaces involves time-dependent effects, such as surface deformations, non-uniform filling of surface pores within or outside the contact area, and surface chemistries, but the detailed impact of these phenomena on wetting is not entirely clear. Understanding these effects is crucial for designing coatings for a wide range of applications, such as membrane-based oil-water separation and desalination, waterproof linings/windows for automobiles, aircrafts, and naval vessels, and antibiofouling. Herein, we report on time-dependent contact angles of water droplets on a rough polydimethylsiloxane (PDMS) surface that cannot be completely described by the conventional Cassie-Baxter or Wenzel models or the recently proposed Cassie-impregnated model. Shells of sand dollars (Dendraster excentricus) were used as lithography-free, robust templates to produce rough PDMS surfaces with hierarchical, periodic features ranging from 10-7-10-4 m. Under saturated vapor conditions, we found that in the short-term (<1 min), the contact angle of a sessile water droplet on the templated PDMS, θSDT = 140° ± 3°, was accurately described by the Cassie-Baxter model (predicted θSDT = 137°); however, after 90 min, θSDT fell to 110°. Fluorescent confocal microscopy confirmed that the initial reduction in θSDT to 110° (the Wenzel limit) was primarily a Cassie-Baxter to Wenzel transition during which pores within the contact area filled gradually, and more rapidly for ethanol-water mixtures. After 90 min, the contact line of the water droplet became pinned, perhaps caused by viscoelastic deformation of the PDMS around the contact line, and a significant volume of water began to flow from the droplet to pores outside the contact region, causing θSDT to decrease to 65° over 48 h on the rough surface. The system we present here to explore the concept of contact angle time dependence (dynamics) and modeling of natural surfaces provides insights into the design and development of long- and short-lived coatings.en
dc.language.isoenen
dc.publisherAmerican Chemical Society (ACS)en
dc.relation.urlhttp://pubs.acs.org/doi/10.1021/acsami.5b10721en
dc.rightsThis document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Materials & Interfaces, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://pubs.acs.org/doi/10.1021/acsami.5b10721.en
dc.titleTime-Dependent Wetting Behavior of PDMS Surfaces with Bio-Inspired, Hierarchical Structuresen
dc.typeArticleen
dc.contributor.departmentWater Desalination and Reuse Research Center (WDRC)en
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Divisionen
dc.identifier.journalACS Applied Materials & Interfacesen
dc.eprint.versionPost-printen
dc.contributor.institutionCalifornia NanoSystems Institute, University of California, Santa Barbara, Santa Barbara, CA 93106, USAen
dc.contributor.institutionDepartment of Chemical Engineering, University of California, Santa Barbara, Santa Barbara, CA 93106, USAen
dc.contributor.institutionCAPES Foundation, Ministry of Education of Brazil, Brasilia–DF, 70.040-020, Brazilen
dc.contributor.institutionMaterials Department, University of California Santa Barbara, Santa Barbara, CA 93106, USAen
dc.contributor.affiliationKing Abdullah University of Science and Technology (KAUST)en
kaust.authorMishra, Himanshuen
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