Javier Vázquez

Multi-purpose optoelectronic instrument for monitoring the alcoholic fermentation of wine

The ordinary procedure to monitor the progress of wine fermentation relies on manual measurements of its density (related to sugar and ethanol content) as must gradually turns into wine. Such measurements are performed on samples extracted and analyzed at least once a day for more than fifteen days, which makes the process awkward and time-consuming for enologists. In order to contribute to the automatic supervision of the fermentation process, an instrument has been designed to simultaneously record a number of essential properties related to the wine fermentation, like refractive index n and optical densities at three wavelengths necessary to determine the chromatic characteristics of red wine, which are all liable to be recorded in real time by optical means. Additionally, we demonstrate that the variations of the refractive index during the fermentation of white must samples constitute a way to assess the status of the process as useful as the density variations traditionally recorded, which are not easily measurable on-line by optical techniques.

Microsystem for Real Time High Resolution Measurement of Cell Forces

A variety of methods are available for monitoring of cell forces. In this paper, a novel approach using an in-plane deformable microsystem is utilized in which displacements induced by cultured cells are measured via optical profilometry. The high resolution obtainable from profilometry gives an order of magnitude improvement in measurement resolution compared to conventional optical techniques and demonstrates a spatial measurement resolution of 12 nm (126 nN). The work focuses on both fixed and living fibroblasts and epithelial cells with estimates of forces exerted significantly higher using living cells compared to fixed cells. The methodology was developed to give no restriction to the cell environment, thereby allowing the potential for a broad range of experiments in the field.

Coupling factor of a weak inductive coupling in a 2-kW power transfer system with a 125-mm air gap for electric vehicle chargers

This paper describes two methods intended to obtain the coupling factor k of an inductive coupling stage constructed to transfer power to a load in a 2-kW experimental prototype designed for wireless battery charging of electric vehicles. The air gap between the primary and the secondary windings of the inductive coupling is set to 125 mm. The first approach, purely analytical, relies on Neumanns formula to calculate the mutual inductance of two coaxial rectangles and leads to a first estimate of the coupling factor. The second approach is more accurate and combines experimental data measured for three different resistance loads with simulations provided by a PSpice circuit model of the laboratory prototype. The coupling factor obtained with this empirical method is 0.235, in good agreement with the low coupling factors expected for a weak inductive coupling. The developed simulation model, that proved suitable to figure out the coupling factor for the air gap under study, can be applied to any air gap of practical interest in electric vehicle chargers.

A microsystem for high resolution measurement of cell forces

A variety of methods are available for monitoring of cell forces. Here we report on a novel approach utilising optical profilometry within a liquid to measure in-plane displacements induced by cells as they are cultured in a microsystem. The high resolution obtainable from profilometry gives an order of magnitude improvement in measurement resolution compared to conventional optical techniques, a repeatability of 4nm being achieved in this work. The methodology is developed to give no restriction to the cell environment, thereby allowing the potential for a broad range of experiments in the field.

Simulation and characterization of interdigitated microsensor electrodes for DNA detection

Interdigital (IDT) microsensors are one of the most commonly used periodic microelectrode devices in a wide range of fields such as microelectromechanical systems (MEMS), telecommunications, chemical sensing, etc. IDT biochemical sensors targeted towards the direct detection of immobilized ssDNA (single strand nucleic acid sequences) and the subsequent hybridization with the complementary strand are currently an area of significant research interest. The most common outputs of measurement are changes in resistance and capacitance between electrodes as a result of changes in the conductivity or dielectric constant of a thin layer of material or solution coating the IDT device, which contains the oligomeric DNA of interest. DNA may be immobilized on both the electrode surfaces and the interdigital spaces or only on the latter, depending on the method used for the chemical modification of the sensor surface. In this work, various IDT designs are explored from the point of view of sensitivity to the changes in impedance associated with modifications in the conductivity of the material near the electrodes. The designs are studied by an electroquasistatics, finite element method-based 3D model to simulate the variation of IDT sensor impedance. A range of device geometries are considered, with particular attention paid to the width of the fingers relative to the period, or metallization ratio. Our results show that low metallization ratios lead to better impedance sensitivity. The simulation models have also been checked experimentally with commercially available IDTs, where a good agreement has been obtained between calculated and measured impedance.

Contribution of concentrator photovoltaic installations to grid stability and power quality

Large-scale integration of Photovoltaic (PV) generation systems, including Concentrator Photovoltaic (CPV) technologies, will require the contribution and support of these technologies to the management and stability of the grid. New regulations and grid codes for PV installations in countries such as Spain have recently included dynamic voltage control support during faults. The PV installation must stay connected to the grid during voltage dips and inject reactive power in order to enhance the stability of the system. The existing PV inverter technologies based on the Voltage-Source Converter (VSC) are in general well suited to provide advanced grid-support characteristics. Nevertheless, new advanced control schemes and monitoring techniques will be necessary to meet the most demanding requirements.