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dc.contributor.authorArunachalam, Sankara
dc.contributor.authorDomingues, Eddy M
dc.contributor.authorDas, Ratul
dc.contributor.authorNauruzbayeva, Jamilya
dc.contributor.authorButtner, Ulrich
dc.contributor.authorSyed, Ahad
dc.contributor.authorMishra, Himanshu
dc.identifier.citationArunachalam, S., Domingues, E. M., Das, R., Nauruzbayeva, J., Buttner, U., Syed, A., & Mishra, H. (2020). Rendering SiO2/Si Surfaces Omniphobic by Carving Gas-Entrapping Microtextures Comprising Reentrant and Doubly Reentrant Cavities or Pillars. Journal of Visualized Experiments, (156). doi:10.3791/60403
dc.description.abstractWe present microfabrication protocols for rendering intrinsically wetting materials repellent to liquids (omniphobic) by creating gas-entrapping microtextures (GEMs) on them comprising cavities and pillars with reentrant and doubly reentrant features. Specifically, we use SiO2/Si as the model system and share protocols for two-dimensional (2D) designing, photolithography, isotropic/anisotropic etching techniques, thermal oxide growth, piranha cleaning, and storage towards achieving those microtextures. Even though the conventional wisdom indicates that roughening intrinsically wetting surfaces (θo < 90°) renders them even more wetting (θr < θo < 90°), GEMs demonstrate liquid repellence despite the intrinsic wettability of the substrate. For instance, despite the intrinsic wettability of silica θo ≈ 40° for the water/air system, and θo ≈ 20° for the hexadecane/air system, GEMs comprising cavities entrap air robustly on immersion in those liquids, and the apparent contact angles for the droplets are θr > 90°. The reentrant and doubly reentrant features in the GEMs stabilize the intruding liquid meniscus thereby trapping the liquid-solid-vapor system in metastable air-filled states (Cassie states) and delaying wetting transitions to the thermodynamically-stable fully-filled state (Wenzel state) by, for instance, hours to months. Similarly, SiO2/Si surfaces with arrays of reentrant and doubly reentrant micropillars demonstrate extremely high contact angles (θr ≈ 150°-160°) and low contact angle hysteresis for the probe liquids, thus characterized as superomniphobic. However, on immersion in the same liquids, those surfaces dramatically lose their superomniphobicity and get fully-filled within <1 s. To address this challenge, we present protocols for hybrid designs that comprise arrays of doubly reentrant pillars surrounded by walls with doubly reentrant profiles. Indeed, hybrid microtextures entrap air on immersion in the probe liquids. To summarize, the protocols described here should enable the investigation of GEMs in the context of achieving omniphobicity without chemical coatings, such as perfluorocarbons, which might unlock the scope of inexpensive common materials for applications as omniphobic materials. Silica microtextures could also serve as templates for soft materials.
dc.description.sponsorshipHM acknowledges funding from King Abdullah University of Science and Technology (KAUST).
dc.publisherMyJove Corporation
dc.rightsArchived with thanks to Journal of visualized experiments : JoVE
dc.rights.uriCC BY-NC-ND 3.0
dc.titleRendering SiO2/Si Surfaces Omniphobic by Carving Gas-Entrapping Microtextures Comprising Reentrant and Doubly Reentrant Cavities or Pillars.
dc.contributor.departmentWater Desalination and Reuse Research Center (WDRC)
dc.contributor.departmentEnvironmental Science and Engineering Program
dc.contributor.departmentCore Labs, King Abdullah University of Science and Technology (KAUST).
dc.contributor.departmentBiological and Environmental Sciences and Engineering (BESE) Division
dc.identifier.journalJournal of visualized experiments : JoVE
kaust.personArunachalam, Sankara
kaust.personDomingues, Eddy M
kaust.personDas, Ratul
kaust.personNauruzbayeva, Jamilya
kaust.personButtner, Ulrich
kaust.personSyed, Ahad
kaust.personMishra, Himanshu

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