title: Evaporative gold nanorod assembly on chemically stripe-patterned gradient surfaces.
abstract: Experimentally we explore the potential of using pre-defined motion of a receding contact line to control the deposition of nanoparticles from suspension. Stripe-patterned wettability gradients are employed, which consist of alternating hydrophilic and hydrophobic stripes with increasing macroscopic surface energy. Nanoparticle suspensions containing nanorods and nanospheres are deposited onto these substrates and left to dry. After moving over the pattern and evaporation of the solvent, characteristic nanoparticle deposits are found. The liquid dynamics has a pronounced effect on the spatial distribution. Nanoparticles do not deposit on the hydrophobic regions; there is high preference to deposit on the wetting stripes. Moreover, the fact that distributed nanoparticle islands are formed suggests that the receding of the contact line occurs in a stick-slip like fashion. Furthermore, the formation of liquid bridges covering multiple stripes during motion of the droplet over the patterns is modeled. We discuss their origin and show that the residue after drying, containing both nanoparticles and the stabilizing surfactant, also resembles such dynamics. Finally, zooming into individual islands reveals that highly selective phase separation occurs based on size and shape of the nanoparticles.
authors.affiliation: Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands.
authors.forename: Imtiaz
authors.initials: I
authors.lastname: Ahmad
authors.affiliation: Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands.
authors.forename: H Patrick
authors.initials: HP
authors.lastname: Jansen
authors.affiliation: Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands.
authors.forename: Jeroen
authors.initials: J
authors.lastname: van Swigchem
authors.affiliation: Institute of Physics, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben, Austria; Christian Doppler Laboratory for Surface Chemical and Physical Fundamentals of Paper Strength, Graz University of Technology, 8010 Graz, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Ganser
authors.affiliation: Institute of Physics, Montanuniversitaet Leoben, Franz-Josef-Strasse 18, A-8700 Leoben, Austria.
authors.forename: Christian
authors.initials: C
authors.lastname: Teichert
authors.affiliation: Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands.
authors.forename: Harold J W
authors.initials: HJ
authors.lastname: Zandvliet
authors.affiliation: Physics of Interfaces and Nanomaterials, MESA+ Institute for Nanotechnology, University of Twente, PO Box 217, 7500AE Enschede, The Netherlands. Electronic address: e.s.kooij@utwente.nl.
authors.forename: E Stefan
authors.initials: ES
authors.lastname: Kooij
keywords: Directional wetting; Evaporative assembly; Gold nanorods