Silicon-technology based microreactors for high-temperature heterogeneous partial oxidation reactions

In this thesis the results of a study into the feasibility of silicon-technology based microreactors for fast oxidation reactions have been discussed. When designed properly, silicon microreactors are suitable for studying heterogeneous gas phase reactions, such as reaction kinetics of direct catalytic partial oxidation of methane into synthesis gas. This thesis focused on the design and realization of silicon-technology based micro flow reactors that are to be used for research on high-temperature heterogeneous gas phase reactions

Silicon-based microreactors as research tools in chemistry

In this contribution suitability of silicon-technology based microreactors for performing research on reactions where temperature control is essential is discussed. The versatility of silicon micromachining technology is elucidated by describing the fabrication and performance of two types of microreactors for studying Rh-catalyzed gas phase reactions. Depending on the design of the microreactor, working temperatures up to 800 degrees C can be obtaine

Performance of Spectrophotometric and Fluorometric DNA Quantification Methods

Accurate DNA quantification is a highly important method within molecular biology. Methods widely used to quantify DNA are UV spectrometry and fluorometry. In this research, seven different DNA samples and one blank (MilliQ ultrapure water) were quantified by three analysts using one spectrophotometric (i.e., a NanoDrop instrument) and three fluorometric (i.e., the AccuGreen High Sensitivity kit, the AccuClear Ultra High Sensitivity kit, and the Qubit dsDNA HS Assay kit) methods. An analysis of variance (ANOVA) scheme was used to determine the influence of the analyst, the method, and the combination of analyst and method, on DNA quantification. For most samples, the measured DNA concentration was close to or slightly above the concentration of 10 ng/μL as specified by the supplier. Results obtained by the three analysts were equal. However, it was found that, compared to the fluorometric kits, the used spectrophotometric instrument in the case of fish DNA samples tends to overestimate the DNA concentration. Therefore, if sufficient sample volume is available, a combination of a spectrophotometric and a fluorometric method is recommended for obtaining data on the purity and the dsDNA concentration of a sample

Local deposition and patterning of catalytic thin films in microsystems

The local deposition of catalysts is desired in a wide range of catalytic microsystems (microreactors and sensors). In this study, we investigate technologies enabling deposition and patterning of catalyst thin films in a manner compatible with standard micromachining processes. We evaluate and compare deposition techniques based on a combination of a self-assembly, soft-lithography and conventional micromachining. Platinum (Pt) and palladium (Pd) were used as model catalysts, both as a sputtered thin film and as nanoparticles supported on γ-alumina. The thin films were characterized and tested in terms of their catalytic activity based on CO chemisorption measurements, stability and reproducibilit

Synthesis and Characterization of Boron Thin Films Using Chemical and Physical Vapor Depositions

Boron as thin film material is of relevance for use in modern micro- and nano-fabrication technology. In this research boron thin films are realized by a number of physical and chemical deposition methods, including magnetron sputtering, electron-beam evaporation, plasma enhanced chemical vapor deposition (CVD), thermal/non-plasma CVD, remote plasma CVD and atmospheric pressure CVD. Various physical, mechanical and chemical characteristics of these boron thin films are investigated, i.e., deposition rate, uniformity, roughness, stress, composition, defectivity and chemical resistance. Boron films realized by plasma enhanced chemical vapor deposition (PECVD) are found to be inert for conventional wet chemical etchants and have the lowest amount of defects, which makes this the best candidate to be integrated into the micro-fabrication processes. By varying the deposition parameters in the PECVD process, the influences of plasma power, pressure and precursor inflow on the deposition rate and intrinsic stress are further explored. Utilization of PECVD boron films as hard mask for wet etching is demonstrated by means of patterning followed by selective structuring of the silicon substrate, which shows that PECVD boron thin films can be successfully applied for micro-fabrication

Evidence of wettability variation on carbon nanofiber layers grown on oxidized silicon substrates

This paper describes how layers of carbon nanofibers (CNFs) with a controllable wettability can be synthesized by means of thermal catalytic chemical vapor deposition on nickel-based thin films on oxidized silicon supports. In order to achieve well-adhesive CNF-layers with a uniform surface coverage and tunable wettability without the necessity of post-synthesis treatments, a series of synthesis parameters is investigated: the pretreatment atmosphere (hydrogen or oxygen; 2 h, 500 °C), the use of ethylene (C2H4) or an ethylene/hydrogen (C2H4/H2) mixture as hydrocarbon source, and the growth time (in the range 5–60 min). Fast and uniform CNF-growth is found on reduced Ni-based thin films using C2H4/H2 at a synthesis temperature of 635 °C. The CNF-layers on Ni are superhydrophobic or highly hydrophobic for all growth times, but their adhesion to the support is poor for growth times >30 min. In contrast, the adhesion of CNF-layers on Ni/Ta is excellent. Moreover, the wettability of these as-synthesized CNF-layers can be controlled by variation of the growth time: from superhydrophobic (⩽10 min) to hydrophilic (⩾50 min). CNF-layers with such tunable wettability can be easily integrated in flow channels of silicon-based microfluidic systems, thereby offering numerous applications

An all-glass microfluidic network with integrated amorphous silicon photosensors for on-chip monitoring of enzymatic biochemical assay

A lab-on-chip system, integrating an all-glass microfluidics and on-chip optical detection, was developed and tested. The microfluidic network is etched in a glass substrate, which is then sealed with a glass cover by direct bonding. Thin film amorphous silicon photosensors have been fabricated on the sealed microfluidic substrate preventing the contamination of the micro-channels. The microfluidic network is then made accessible by opening inlets and outlets just prior to the use, ensuring the sterility of the device. The entire fabrication process relies on conventional photolithographic microfabrication techniques and is suitable for low-cost mass production of the device. The lab-on-chip system has been tested by implementing a chemiluminescent biochemical reaction. The inner channel walls of the microfluidic network are chemically functionalized with a layer of polymer brushes and horseradish peroxidase is immobilized into the coated channel. The results demonstrate the successful on-chip detection of hydrogen peroxide down to 18 mu M by using luminol and 4-iodophenol as enhancer agent

Understanding blood oxygenation in a microfluidic meander double side membrane contactor

Lung disease is one of the most important causes of high morbidity in preterm infants. In this work, we study a simple and easy to fabricate microfluidic device that demonstrates a great potential for blood oxygenation. A meander type architecture with double side vertical membrane arrangement has been selected as reference model to investigate the oxygenation process. The design criteria for the fabricated devices has been to maximize the oxygen saturation level while ensuring the physiological blood flow in order to avoid thrombus formation and channel blockage during operation. A mathematical model for the oxygen transfer has been developed and validated by the experimental study. The obtained results demonstrate that blood was successfully oxygenated up to approximately 98% of O-2 saturation and that the oxygen transfer rate at 1 mL/min blood flow rate was approximately 92 mL/minm(2). Finally, a sensitivity analysis of the key parameters, i.e. size of the channel, oxygen concentration in the gas phase and oxygen permeation properties of the membrane, is carried out to discuss the performance limits and to settle the guidelines for future developments.The authors would like to acknowledge the financial support from the Government of Aragón and the Education, Audiovisual and Culture Executive Agency (EU-EACEA) within the EUDIME - 'Erasmus Mundus Doctorate in Membrane Engineering' program (FPA 2011-0014, SGA 2012-1719, http://eudime.unical.it). CIBER-BBN is an initiative funded by the VI National R&D&i Plan 2008-2011 financed by the Instituto de Salud Carlos III with the assistance of the European Regional Development Fund. Authors acknowledge the LMA-INA for offering access to their instruments and expertise