Integrated optical sensors for disposable microfluidics

Optical chemical sensors are established process monitoring tools in industry and research laboratories. Optical chemical sensors basically comprise of luminescent indicator dye based in a host polymer. They are easy to integrate, non-invasive, do not need any reference element and can be read-out contactless from outside. However, to fully exploit the potential in microfluidic or organ-on- chip devices, the sensors have to fulfil several demands including high brightness, capability to be applied as thin film, excellent photo-stability, cheap and accurate read-out systems, ease in use (simple calibration and drift free), simple mass production compatible preparation steps, compatibility with the chip materials, resistance towards γ-sterilisation and no toxicity. We present sensors for oxygen and pH fulfilling these demands. Our sensors can be excited with red-light and emit light in the near infra-red range (\u3c700 nm). This suppresses background fluorescence and scattering from biological material. Sensor layers or spots are deposited with inkjet-based micro-dispensing or air-brush spraying with good adherence on glass or polymeric materials. A modified miniaturized phase-fluorimeter in a foot-print of a memory stick enables the read-out of sensor sizes below 100 micrometers. The sensor enable dynamic cell culturing and monitoring of cell metabolism in a microfluidic environment. We will give examples of oxygen sensors in a organ-on-chip model and pH sensors in cell cultures. Please click Additional Files below to see the full abstract

Towards improved monitoring of offshore carbon storage: A real-world field experiment detecting a controlled sub-seafloor CO2 release

Carbon capture and storage (CCS) is a key technology to reduce carbon dioxide (CO2) emissions from industrial processes in a feasible, substantial, and timely manner. For geological CO2 storage to be safe, reliable, and accepted by society, robust strategies for CO2 leakage detection, quantification and management are crucial. The STEMM-CCS (Strategies for Environmental Monitoring of Marine Carbon Capture and Storage) project aimed to provide techniques and understanding to enable and inform cost-effective monitoring of CCS sites in the marine environment. A controlled CO2 release experiment was carried out in the central North Sea, designed to mimic an unintended emission of CO2 from a subsurface CO2 storage site to the seafloor. A total of 675 kg of CO2 were released into the shallow sediments (∼3 m below seafloor), at flow rates between 6 and 143 kg/d. A combination of novel techniques, adapted versions of existing techniques, and well-proven standard techniques were used to detect, characterise and quantify gaseous and dissolved CO2 in the sediments and the overlying seawater. This paper provides an overview of this ambitious field experiment. We describe the preparatory work prior to the release experiment, the experimental layout and procedures, the methods tested, and summarise the main results and the lessons learnt

Development of a fully integrated falling film microreactor for gas–liquid–solid biotransformation with surface immobilized O2‐dependent enzyme

Although the positive effect that cellulose nanofibers (CNF) can have on paper strength is known, their effect on flocculation during papermaking is not well understood, and most relevant studies have been carried out in presence of only cationic starch. Flocculation is the key to ensuring retention of fibers, fines, and fillers, and furthermore floc properties have a great influence on paper quality. The aim of this research is to study the interactions between CNF and flocculants by assessing the effect of two types of CNF, from eucalyptus and corn, on the flocculation process induced by three different retention systems [adual system, polyvinylamine (PVA), and cationic starch as reference]. The results showed that CNF interacted with the flocculants in different ways, affecting flocculation efficiency and floc properties. In general, addition of CNF increased floc stability and minimized overdosing effects. Moreover, presence of CNF increased floc size for given PVA dose; therefore, CNF addition could contribute to improve the wet end in the paper machine if combined with the optimal flocculant and dose.Depto. de Ingeniería Química y de MaterialesFac. de Ciencias QuímicasTRUEpu

Wide-range optical pH imaging of cementitious materials exposed to chemically corrosive environments

The pH of concrete-based material is a key parameter for the assessment of its stability and durability, since a change in pH is usually associated with major types of chemical degradation such as carbonation, leaching and acid attacks. Conventional surface pH measurements with potentiometric flat surface electrodes have low spatial resolution, whereas optical pH visualization with indicator dyes (phenolphthalein) only indicates the areas with higher or lower pH than the pKa of the indicator. In this regard, it is key to develop wide-range imaging systems, enabling accurate and spatially resolved determination of pH variability for an advanced knowledge of degradation mechanisms. This contribution presents the enhancements made for a high-resolution optical pH imaging system based on fluorescent aza-BODIPY indicator dyes. The measurement range was increased to 6 pH units (pH 6.5 to pH 12.5) by a combination of two indicator dyes. Moreover, background scattering effects were sufficiently eliminated. With the improved sensor foils steep pH gradients (up to 3 pH units within 2 mm) were successfully recorded in various concrete specimens using a macro lens reaching a resolution of down to 35 µm per pixel