Mesa+ Meeting

Research Area Sessions

1Advanced materials & devices, chaired by dr.ir. Floris Zwanenburg & dr.ir. Gertjan Koster

2Fluidics & microsystems, chaired by dr.ir. Mathieu Odijk & dr. David Fernandez Rivas

3Photonics & (bio)systems, chaired by dr.ir. Annemarie Huijser & prof.dr. Pepijn Pinkse

4Soft matter & devices, chaired by dr. Saskia Lindhoud & dr. Tibor Kudernac

Fluidics & microsystems (ROOM 6)

Chairs: dr.ir. Mathieu Odijk (BIOS Lab-on-a-chip) & dr. David Fernandez Rivas (Mesoscale Chemical Systems)

INTRODUCTION

PROGRAM

ABSTRACTS

Microfluidic stripline-based NMR flow probe for in-line monitoring of catalytic styrene Hydrogenation
Hainan Zhang MSc. (Mesoscale Chemical Systems)

We present a novel, optimized microfluidic stripline-based flow probe for high sensitivity and resolution Nuclear Magnetic Resonance (NMR) spectroscopy at 600 MHz. The unique characteristics of the probe are that it operates with a very minute amount of sample, of the order of hundreds of nanoliters, under high pressure conditions. As an example of an application of the probe, we have performed styrene hydrogenation experiments over an encapsulated Pd catalyst, in a flow system in which the NMR probe is in line with the catalytic microreactor. The obtained well-defined NMR spectra allow to make accurate calculations of the conversion of the substrate, and in future could become a valuable tool for screening catalysts and catalytic reactions under real processing conditions, or for extracting samples from a larger higher pressure reactor, without the need for pressure release, therewith avoiding shifts in reaction composition that normally may occur by decreasing the pressure.

Control on droplet coalescence and splashing for the generation of extreme UV lithography
Pascal Sleutel MSc. (Physics of Fluids)

Diffusio-phoresis of photocatalytic particles under self-generated concentration gradients
Aura Visan MSc. (Soft Matter, Fluidics and Interfaces)

The generation of flow within the interfacial structure due to concentration gradients was described quantitatively for the first time by Anderson [1] and extended by Ajdari and Bocquet [2] for solvophobic surfaces. The flow is driven by an osmotic pressure gradient which builds up inside the interfacial layer where the interaction potential between the chemical species and solid spans (Fig. 1). Moreover, if the surface is reactive, the diffusio-osmotic flow could be promoted without any external input, through self-generated concentration gradients. If the solid surface is not immobilized, e.g in a colloidal system, the surface flow will propel small particles.

In this project, the migration of photocatalytic particles (TiO₂) under self-generated concentration gradients is studied systematically in a microreactor where an aqueous solution of an organic contaminant is contacted under continuous flow with a particle suspension containing various concentrations of the same contaminant (Fig 2). When UV light is turned on, the photocatalytic particles decompose the contaminant lowering the concentration inside the colloidal stream. The difference in concentration that is generated via the photocatalytic reaction leads to the migration of particles toward the higher concentration site.

The effects of electric fields on dropwise condensation
Davood Baratian MSc. (Physics of Complex Fluids)

Dropwise condensation occurs when vapor condenses on a low surface energy surface, and the substrate is just partially wetted by the condensate. Dropwise condensation has attracted significant attention due to its reported superior heat transfer performance compared to filmwise condensation. Extensive research efforts are focused on how to promote, and enhance dropwise condensation by considering both physical and chemical factors. We have studied electrowetting-actuated condensation on hydrophobic surfaces, aiming for enhancement of heat transfer in dropwise condensation. The idea is to use suitably structured patterns of micro-electrodes that generate a heterogeneous electric field at the interface and thereby promote both the condensation itself and the shedding of condensed drops. Comforting the shedding of droplets on electrowetting-functionalized surfaces allows more condensing surface area for re-nucleation of small droplets, leading to higher condensation rates. Possible applications of this innovative concept include heat pipes for (micro) coolers in electronics as well as in more efficient heat exchangers.