Fluidics

Fluidics

chaired by Jacco Snoeijer & Mathieu Odijk

 

11.45-12.00

Surface flows inside catalytic dead-end pores

Aura Visan (SFI)

12.05-12.20

Free flow depletion zone isotachophoresis (FFdz-ITP)

Vasilis Papadimitriou (BIOS)

12.25-12.40

Mesoscopic modelling of ink imbibition in paper

Thejas Hulikal Chakrapani (MSM)

12.45-13.00

Self-propelled drops motion on a cryogenic bath

Anaïs Gauthier (PoF)

Abstracts

Surface flows inside catalytic dead-end pores, Aura Visan (SFI)

Quite inconceivable until now, convective transport is possible inside catalytic dead-end pores. The surface flow which originates in the osmotic pressure gradient and diffusion potential in case of charged species, replenishes the catalytic pores with fresh solution, having a consequential impact on the conversion. This additional mass transport does not require any external input. It spontaneously arises when the configuration of the catalyst facilitates the development of significant gradients with respect to the bulk solution. Knowing how to quantify this transport mechanism, we can purposely design the catalytic matrix in order to intensify the flow. These findings challenge the generally accepted narrative on mass transport inside porous catalysts and propose a new direction for material fabrication and reactor design.

Free flow depletion zone isotachophoresis (FFdz-ITP), Vasilis Papadimitriou (BIOS)

Lab-on-chip systems provide an appealing platform for electrophoretic separations due to the high controllability of fluid flow and electric fields on the micrometer scale. The inherent disadvantage of miniaturized separation techniques, their low sample throughput, is addressed by two special classes of techniques, ones that combine separation and focusing and ones that use the free-flow format. In this talk we will introduce Free-Flow depletion zone Isotachophoresis (FFdz-ITP), a free-flow separation and focusing technique that does not require any sample or special electrolyte preparation; and allows high throughput extraction of separated and concentrated analytes directly out of blood plasma.

Mesoscopic modelling of ink imbibition in paper, Thejas Hulikal Chakrapani (MSM)

Jettable ink is a mixture of water, co-solvent (glycerol), surfactants and pigment particles for color. The typical size of these pigment particles lie between 20-200 nm. On the other hand, office paper consists of dried hollow natural fibers of ~2mm length, compressed into a 100 micrometer layer with a complex network of pores which are tens of nanometers in size. In addition, paper coatings are granular in nature and contain pores of width between 10-400 nm. Hence, ink-imbibition into paper is a highly complex process which encompasses the complexity of the fluid, complex geometry of paper, and the multiscale nature of the problem. 

We have recently started on this topic, using particle-based mesoscopic simulations. The first topic to be presented is the surface-tension-driven flow of various fluids into cylindrical pores, to assess the impact of the fluid on the expected Lucas-Washburn imbibition rate. Next, results will be presented on the surface-tension-driven flow of a simple fluid into a variety of idealized arrays of (hollow) cylinders, representing our first step to a model for paper.

Self-propelled drops motion on a cryogenic bath, Anaïs Gauthier (PoF)

An inverse Leidenfrost state can happen when ambient temperature drops are deposited on a liquid nitrogen bath: evaporation of the pool is fast enough to generate a vapor film that maintains drops in levitation. We consider here the dynamics of such levitating drops. We show first that the motion of an isolated suspended drop is not random: it is observed to self-propel, and it keeps gliding across the bath in straight lines for minutes. We explain the origin of self-propulsion, that lies in very small deformations of the bath. Then, we study the situation of two gliding drops approaching each other. Each drop deforms the surface of the bath around it at the millimeter-scale, and interaction between the two menisci generates mutual attraction, in a way that shares similarities with gravitational attraction between planets. However, the fundamental change in the nature of the attractive potential makes drop trajectories very different from the classical Keplerian orbits, which we discuss.