title: Patterned Polymer Coatings Increase the Efficiency of Dew Harvesting.
abstract: Micropatterned polymer surfaces, possessing both topographical and chemical characteristics, were prepared on three-dimensional copper tubes and used to capture atmospheric water. The micropatterns mimic the structure on the back of a desert beetle that condenses water from the air in a very dry environment. The patterned coatings were prepared by the dewetting of thin films of poly-4-vinylpyridine (P4VP) on top of polystyrene films (PS) films, upon solvent annealing, and consist of raised hydrophilic bumps on a hydrophobic background. The size and density distribution of the hydrophilic bumps could be tuned widely by adjusting the initial thickness of the P4VP films: the diameter of the produced bumps and their height could be varied by almost 2 orders of magnitude (1-80 μm and 40-9000 nm, respectively), and their distribution density could be varied by 5 orders of magnitude. Under low subcooling conditions (3 °C), the highest rate of water condensation was measured on the largest (80 μm diameter) hydrophilic bumps and was found to be 57% higher than that on flat hydrophobic films. These subcooling conditions are achieved spontaneously in dew formation, by passive radiative cooling of a surface exposed to the night sky. In effect, the pattern would result in a larger number of dewy nights than a flat hydrophobic surface and therefore increases water capture efficiency. Our approach is suited to fabrication on a large scale, to enable the use of the patterned coatings for water collection with no external input of energy.
authors.affiliation: School of Chemistry and ‡School of Chemical and Biomolecular Engineering, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Omar
authors.initials: O
authors.lastname: Al-Khayat
authors.affiliation: School of Chemistry and ‡School of Chemical and Biomolecular Engineering, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Jun Ki
authors.initials: JK
authors.lastname: Hong
authors.affiliation: School of Chemistry and ‡School of Chemical and Biomolecular Engineering, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: David M
authors.initials: DM
authors.lastname: Beck
authors.affiliation: School of Chemistry and ‡School of Chemical and Biomolecular Engineering, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Andrew I
authors.initials: AI
authors.lastname: Minett
authors.affiliation: School of Chemistry and ‡School of Chemical and Biomolecular Engineering, The University of Sydney , Sydney, New South Wales 2006, Australia.
authors.forename: Chiara
authors.identifier: http://orcid.org/0000-0001-6058-0885
authors.initials: C
authors.lastname: Neto
keywords: biomimetic; condenser; dew; polymers; thin films; water harvesting