Computational investigation of actuation mechanisms of droplets on porous air-permeable substrates.

We study the actuation of droplets on porous substrates by air that permeates through pores. Air pockets are created between the droplets and the substrate which, eventually, incite the droplets to a quasi-moving state. We observe this mechanism computationally and verify it experimentally, using various case studies involving water droplets of different volume that are initially pinned on a porous substrate which has been set to different inclination levels and start to slide down when actuated by permeating air.

Controlled deposition of fullerene derivatives within a graphene template by means of a modified Langmuir-Schaefer method.

The scientific and technological potential of graphene's includes the development of light, open 3D hybrid structures with high surface area, tunable pore size and aromatic functionalities. Towards this aim, we describe a scalable and low-cost bottom-up approach that combines self-assembly and Langmuir-Schaefer deposition for the production of fullerene-intercalated graphene oxide hybrids. This method uses graphene oxide (GO) nanosheets as template for the attachment of two types of fullerene derivatives (bromo-fullerenes, CBr and fullerols, C(OH)) in a bi-dimensional arrangement, allowing a layer-by-layer growth with control at nanoscale.

Droplet Mobility Manipulation on Porous Media Using Backpressure.

Wetting phenomena on hydrophobic surfaces are strongly related to the volume and pressure of gas pockets residing at the solid-liquid interface. In this study, we explore the underlying mechanisms of droplet actuation and mobility manipulation when backpressure is applied through a porous medium under a sessile pinned droplet. Reversible transitions between the initially sticky state and the slippery states are thus incited by modulating the backpressure.

Plasma directed assembly and organization: bottom-up nanopatterning using top-down technology.

Fabrication of periodic nanodot or nanocolumn arrays on surfaces is performed by top-down lithographic procedures or bottom-up self-assembly methods, which both make use of plasma etching to transfer the periodic pattern. Could plasma etching alone act as an assembly--organization method to create the pattern and then transfer it to the substrate? We present data that support this idea and propose a mechanism of periodicity formation where etching and simultaneous deposition take place.

Mechanisms of oxygen plasma nanotexturing of organic polymer surfaces: from stable super hydrophilic to super hydrophobic surfaces.

Plasma processing is used to fabricate super hydrophilic or super hydrophobic polymeric surfaces by means of O2 plasma etching of two organic polymers, namely, poly(methyl methacrylate) (PMMA) and poly(ether ether ketone) (PEEK); a C4F8 plasma deposition follows O2 plasma etching, if surface hydrophobization is desired. We demonstrate high aspect ratio pillars with height ranging from 16 nm to several micrometers depending on the processing time, and contact angle (CA) close to 0 degrees after O2-plasma treatment or CA of 153 degrees (with CA hysteresis lower than 5 degrees) after fluorocarbon deposition. Super hydrophobic surfaces are robust and stable in time; in addition, aging of super hydrophilic surfaces is significantly retarded because of the beneficial effect of the nanotextured topography.