Biomimetic Creation of Hierarchical Surface Structures by Combining Colloidal Self-Assembly and Au Sputter Deposition

Abstract

Surfaces of hexagonally packed silica spheres have been functionalized with silanes containing different hydrocarbon or fluorocarbon chains. The resulting chemical and physical structures were studied to establish the effect of surface hydrophobicity on the measured contact angles on the rough surfaces. The results were used to assess the effects of surface modifications on the parameters in the Cassie equation. To achieve superhydrophobicity via a biomimetic approach, we created two-scale structures by first forming hexagonally packed SiO2 spheres, followed by Au deposition on the spheres and heat treatment to form Au nanoparticles on sphere surfaces. Contact angles over 160 degrees were achieved. This work provides improved understanding of the effect of the surface roughness and solid surface fraction on superhydrophobicity.

Multiscale patterning of nanocomposite polyelectrolyte/nanoparticle films using inkjet printing and AFM scratching

“…By comparing the static contact angle of a 2 μL droplet of a NaCl solution of polydiallyldimethylammonium chloride (polyDDA) on a hydrophilic glass microscope slide ( figure 1(a)) and on a TFPS terminated, hydrophobic glass slide ( figure 1(b)), it was observed, as expected, that polyDDA exhibited a higher contact angle (∼80°) on the hydrophobised surfaces compared to an untreated glass surface (<5°). The marked increase in contact angle for the CF 3 functionalised surface agreed with previous literature [16].…”

Fabrication of Surfaces with Bimodal Roughness Through Polyelectrolyte/Colloid Assembly

“…This is exemplified by the Lotus effect, in which a dual size roughness seems to be important (Barthlott & Neinhuis, 1997;Patankar, 2004). Raspberry-like surface morphologies were created in different ways : styrene polymerization (Perro et al, 2006;Reculusa et al, 2002) or gold sputtering (Xiu et al, 2006) on silica particles , controlled aggregation of different surface-functionalized silica particles (Ming et al, 2005) or direct electrochemical synthesis of gold microaggregates (Li Z. et al, 2007) and immobilization on a specific substrate. In this paper, we prepare surfaces covered with a homogeneous monolayer of colloidal particles, using adhesion of negatively charged polystyrene latex beads on a polycationprecoated glass substrate.…”

“…In another study, silica particles having different sizes and bearing functional groups were firstly synthesized independently and then mixed to react together. The obtained aggregates were then grafted on a specific substrate to obtain a dual-size roughness surface (Xiu et al, 2006). In another approach, a layer of silica particles in hexagonal close packing was created on a substrate, and gold nanoparticles were formed on the top of the silica spheres by sputtering (Ming et al, 2005).…”

Recent research progress in wettability of colloidal crystals

“…The superhydrophobic surface is also obtained through roughening the latex surface by depositing the nanometer metal particles upon latex spheres. For example, Au [31] or Ag [32] nanoparticles were deposited upon the SiO 2 latex spheres, and the hexagonally packed structure of composite SiO 2 produced superhydrophobic films.…”