Jérôme Gavillet

Surface Coating with Nanofluids: The Effects on Pool Boiling Heat Transfer

Recent research has confirmed a buildup of a thin layer of nanoparticles on the heated surface during nucleate boiling in nanofluids. Most of these studies report no change of heat transfer and, even worse, the presence of heat transfer deterioration. However, a few others report a heat transfer enhancement. In order to understand these controversial results, experiments were performed to explore the mechanism of surface coating during nucleate boiling in nanofluids. The thickness of the nanoparticle layer was observed to depend on the nanoparticles concentration and the experiment duration. Compared to a clean surface, the wettability of the surfaces with a TiO2 nanoparticle layer has been significantly improved. However, up to 50% of heat transfer coefficient deterioration was observed with TiO2-coated surfaces in water pool boiling. An explanation is proposed that involves the role of adhesion energy on heat transfer.

Flow Boiling of Water on Titanium and Diamond-like carbon coated Surfaces in a Microchannel

Experiments were performed to study the effects of surface wettability on flow boiling of water at atmospheric pressure. The test channel is a single rectangular channel 0.5 mm high, 5 mm wide and 180 mm long. The mass flux was set at 100 and 120 kg/m² s and the base heat flux was varied from 30 to 80 kW/m². Water enters the test channel under subcooled conditions. The sample surfaces are titanium (Ti) and diamond-like carbon (DLC) surfaces having a contact angle of 49° and 63°, respectively. The experimental results show different flow patterns that impact the heat transfer significantly. Compared to the Ti surface, the DLC surface shows a deterioration of 10% in heat transfer.

A new technology platform for fully integrated polymer based micro optical fluidic systems

Abstract This paper describes a new technology platform for polymeric micro optical fluidic systems. The platform consists of active and passive optical and fluidic elements for a surface plasmon resonance (SPR) biosensor for the detection of proteins. The platform includes the integration of polymer light emitting diodes, polymer photodiodes as well as polymer based fluidic valves and pressure generation elements. Surface functionalization for micro optical and micro fluidic parts as well as advanced manufacturing methods are other important parts of the presented technology platform.

Nanostructured polymer thin films : Application to biosensors

Damien Dresse Introduction The possibility to modify and control the surface wettability of different materials has attracted signicant scientic and technological interest. Particularly for biological systems (implantable microdevices in the body or microfluidic systems) the hydrophobic and hydrophilic nature of a surface plays a key role on the mediation of solute (e.g. protein) adsorption and cell adhesion [1,2]. Also, surface roughness may amplify hydrophobicity as observed with superhydrophobicity of self-cleaning surfaces like some plant leaves, e.g., lotus [3]. Such an effect can be desirable for channel flows since it can reduce resistance to the flow [4]. Moreover, the clinical use of so-called non-fouling surfaces requires the ability to effectively interface with the biological milieu in a non-immunogenic and stable manner [5]. So to address this twofold request of surfaces having a tuneable physical behaviour towards a liquid sample as well as a natural compatibility with biomarkers carried within the sample suitable polymer films have been developped by Plasma Enchanced Chemical Vapor Deposition (PECVD). These polymers films also have practical uses in the surface modification of all kinds of materials such as binding of biomaterials, dyeing of textiles, catalyst preparation, printability of polymers, adhesion improvement of composite, wettability improvement of materials etc. [5-9]. PECVD films provide unique advantages due to the ability to control topography and film thickness on the micro and nanoscale, and control surface chemistry in a precise manner through chemical coupling and precursors tayloring. The present article is illustrating this technology through the case of application of SEMOFS. SEMOFS is an European project whose aim is to develop technologies, demonstrators and bioprotocols for the polymer based integrated probe card. It applies a label-free optical detection based on surface plasmon resonance (SPR) [10], where biochemical interactions at the sensor surface are monitored by observing the resonant behaviour of surface waves at a thin metal film. Both active and passive optical components (light source, waveguide, detector) as well as fluidic elements for active liquid transport and immobilised biological material (e.g. antibodies) will be integrated in the card. This new type of biosensor concept will