Condensation in Nanoporous Packed Beds.

In materials with tiny, nanometer-scale pores, liquid condensation is shifted from the bulk saturation pressure observed at larger scales. This effect is called capillary condensation and can block pores, which has major consequences in hydrocarbon production, as well as in fuel cells, catalysis, and powder adhesion. In this study, high pressure nanofluidic condensation studies are performed using propane and carbon dioxide in a colloidal crystal packed bed.

Hydrodynamic force between a sphere and a soft, elastic surface.

The hydrodynamic drainage force between a spherical silica particle and a soft, elastic polydimethylsiloxane surface was measured using the colloidal probe technique. The experimental force curves were compared to finite element simulations and an analytical model. The hydrodynamic repulsion decreased when the particle approached the soft surface as compared to a hard substrate.

Superamphiphobic particles: how small can we go?

Water and oil repellent coatings--so-called superamphiphobic coatings--greatly reduce the interaction between a liquid and a solid. So far, only flat or weakly curved superhydrophobic and superamphiphobic surfaces have been designed. This raises the question of whether highly curved structures or microspheres are feasible.

Adhesion of particles with sharp edges to air-liquid interfaces.

In order to study the effect of sharp edges on solid particle adhesion to air-liquid interfaces, spherical colloidal probes were modified with a circumferential cut by focused ion beam milling. The interaction of the modified particles with water drops and bubbles was studied using the colloidal probe technique. When the modified particles were brought into contact with air-liquid interfaces, the contact line was pinned at the edge of the cut.

Detachment force of particles from air-liquid interfaces of films and bubbles.

The detachment force required to pull a microparticle from an air-liquid interface is measured using atomic force microscopy (AFM) and the colloidal probe technique. Water, solutions of sodium dodecyl sulfate (SDS), and silicone oils are tested in order to study the effects of surface tension and viscosity. Two different liquid geometries are considered: the air-liquid interface of a bubble and a liquid film on a solid substrate.

Interaction of a microsphere with a solid-supported liquid film.

The interaction between particles with thin liquid films on solid surfaces was studied by sintering polystyrene microspheres of 4 to 5 microm diameter to the end of atomic force microscope cantilevers. Films of three silicone oils (viscosity 4.6, 9.