Microstructure devices for process intensification: Influence of manufacturing tolerances and measurement uncertainties

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.Process intensification by miniaturization is a common task for several fields of technology. Starting from manufacturing of electronic devices, miniaturization with the accompanying opportunities and problems gained also interest in chemistry and chemical process engineering. While the integration of enhanced functions, e.g. integrated sensors and actuators, is still under consideration, miniaturization itself has been realized in all material classes, namely metals, ceramics and polymers. First devices have been manufactured by scaling down macro-scale devices. However, manufacturing tolerances, material properties and design show much larger influence to the process than in macro scale. Many of the devices generated alike the macro ones work properly, but possibly could be optimized to a certain extend by adjusting the design and manufacturing tolerances to the special demands of miniaturization. Thus, some considerations on the design and production of devices for micro process engineering should be made to provide devices which show reproducible and controllable process behavior. This following publication gives some examples

Heat transfer enhancement with gas-to-gas micro heat exchangers

This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.A characterization of gas-to-gas micro heat exchangers has been performed in terms of pressure drop behavior and heat transfer performance. The gas-to-gas micro heat exchangers differ by partition wall material, partition wall thickness and flow arrangement. The pressure drop behavior has been analyzed due to the pressure losses in different sections of the gas-to-gas micro heat exchangers. Increased pressure losses in front of and behind the micro channels have been detected due to modified geometries in the inlet and outlet distribution chambers. The heat transfer performance has been determined in terms of thermal effectiveness. The comparison among different partition wall materials and partition wall thicknesses showed no significant criteria of the influence of thermal conductivity on the thermal effectiveness. An assessment due to an overall heat exchanger effectiveness has been performed to compare the gas-to-gas micro heat exchangers. For this purpose, the overall exergy loss has been calculated by combination of thermal effectiveness and pressure losses. A strong impact of the exergy loss due to pressure drop has been detected which influences the overall exergy loss of the gas-to-gas micro heat exchangers

Experimental design with integrated temperature sensors in MEMS: an example of application for rarefied gases

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.This paper presents a new MEMS experimental device with integrated temperature sensors. Conventional silicon planar techniques for the fabrication of microelectronic sensors have been used to realize a particular layout, which does not limit the material of the microstructures it can be used with. The study of rarefied gases has been chosen as case study for the validation of the local measuring system. In this work the attention will be focused on the description of the sensor functioning principles and on the presentation of the preliminary results obtained during the calibration procedures. The tests showed promising results for a future development of the sensor design.The European Community’s Seventh Framework Program (FP7/2007-20013) under grant agreement no 215504

Experimental investigation on self-similar heat sinks for liquid cooled electronics

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.The high heat transfer coefficients in microchannels are attractive for direct cooling of electronic systems requiring high heat-flux removal. In this work we are presenting the results of a study on self-similar heat sinks for liquid cooled electronics, made from copper, designed for industrial application and for large scale production. The internal structures, where the most part of the active cooling takes place, have been designed in order to achieve high heat transfer coefficients. As it is almost impossible to validate the design and describe the flow characteristics inside the device via analytical solutions, a well known numerical code was employed to have an insight of the thermal-fluid distributions. It is clear from the simulation that even if copper is characterized by a high thermal conductivity, most of the heat is removed in the overflow-structure, on the side of the device adjacent to the source of heat. This paper attempts to critically analyse a comprehensive list of data as well as plots in order to illustrate the significant characteristics of this type of device

Microstructure devices for water evaporation

This paper was presented at the 2nd Micro and Nano Flows Conference (MNF2009), which was held at Brunel University, West London, UK. The conference was organised by Brunel University and supported by the Institution of Mechanical Engineers, IPEM, the Italian Union of Thermofluid dynamics, the Process Intensification Network, HEXAG - the Heat Exchange Action Group and the Institute of Mathematics and its Applications.Evaporation of liquids is of major interest for many topics in process engineering. One of these is chemical process engineering, where evaporation of liquids and generation of superheated steam is mandatory for numerous processes. Generally, this is performed by use of classical pool boiling and evaporation process equipment, providing relatively limited performance, or by other systems like falling-film evaporators. Due to the advantages of microstructure devices especially in chemical process engineering the interest in microstructure evaporators and steam generators have been increased through the last decade. In this publication different microstructure devices used for evaporation and generation of steam will be described. Starting with simple liquid-heated devices, different types of electrically powered devices containing micro channels as well as non-channel microstructures will be shown. While evaporation of liquids in crossflow and counterflow or co-current flow micro channel devices is possible, it is, in many cases, not possible to obtain superheated steam due to certain boundary conditions. Thus, a new design was proposed to obtain complete evaporation and superheating of the generated steam

Residence time distribution of gas flows in microreactors: Measurement and model comparison

This paper was presented at the 3rd Micro and Nano Flows Conference (MNF2011), which was held at the Makedonia Palace Hotel, Thessaloniki in Greece. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, Aristotle University of Thessaloniki, University of Thessaly, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute.The optimization of microreactor designs for applications in chemical process engineering usually requires knowledge of the residence time distribution (RTD). The applicability of established models to microstructured reactors is currently under debate (Bošković et al. 2008, Günther et al. 2004, Stief et al. 2008). This work provides new experimental data on the residence time distributions of gas flows through different types of microstructured reactors and analyses the data with established RTD models. By this, the dispersion model was found to describe the RTD behavior of gas flow for a majority of the microstructured devices tested. The model could therefore be used to predict the RTD of those reactors.German Federal Ministry of Economics and Technology (IGF Project 15495

The white matter is a pro-differentiative niche for glioblastoma

Glioblastomas are hierarchically organised tumours driven by glioma stem cells that retain partial differentiation potential. Glioma stem cells are maintained in specialised microenvironments, but whether, or how, they undergo lineage progression outside of these niches remains unclear. Here we identify the white matter as a differentiative niche for glioblastomas with oligodendrocyte lineage competency. Tumour cells in contact with white matter acquire pre-oligodendrocyte fate, resulting in decreased proliferation and invasion. Differentiation is a response to white matter injury, which is caused by tumour infiltration itself in a tumoursuppressive feedback loop. Mechanistically, tumour cell differentiation is driven by selective white matter upregulation of SOX10, a master regulator of normal oligodendrogenesis. SOX10 overexpression or treatment with myelination-promoting agents that upregulate endogenous SOX10, mimic this response, leading to niche-independent pre-oligodendrocyte differentiation and tumour suppression in vivo. Thus, glioblastoma recapitulates an injury response and exploiting this latent programme may offer treatment opportunities for a subset of patients

Nanohybrids of Silver Particles Immobilized on Silicate Platelet for Infected Wound Healing

Silver nanoparticles supported on nanoscale silicate platelets (AgNP/NSP) possess interesting properties, including a large surface area and high biocide effectiveness. The nanohybrid of AgNP/NSP at a weight ratio 7/93 contains 5-nm Ag particles supported on the surface of platelets with dimensions of approximately 80×80×1 nm3. The nanohybrid expresses a trend of lower cytotoxicity at the concentration of 8.75 ppm Ag and low genotoxicity. Compared with conventional silver ions and the organically dispersed AgNPs, the nanohybrid promotes wound healing. We investigated overall wound healing by using acute burn and excision wound healing models. Tests on both infected wound models of mice were compared among the AgNP/NSP, polymer-dispersed AgNPs, the commercially available Aquacel, and silver sulfadiazine. The AgNP/NSP nanohybrid was superior for wound appearance, but had similar wound healing rates, vascular endothelial growth factor (VEGF)-A levels and transforming growth factor (TGF)-β1 expressions to Aquacel and silver sulfadiazine

The driver landscape of sporadic chordoma

Chordoma is a malignant, often incurable bone tumour showing notochordal differentiation. Here, we defined the somatic driver landscape of 104 cases of sporadic chordoma. We reveal somatic duplications of the notochordal transcription factor brachyury (T) in up to 27% of cases. These variants recapitulate the rearrangement architecture of the pathogenic germline duplications of T that underlie familial chordoma. In addition, we find potentially clinically actionable PI3K signalling mutations in 16% of cases. Intriguingly, one of the most frequently altered genes, mutated exclusively by inactivating mutation, was LYST (10%), which may represent a novel cancer gene in chordoma