Microfluidics in Membraneless Fuel Cells

In the 1990s, the idea of developing miniaturized devices that integrate functions other than what normally are carried out at the laboratory level was conceived, and the so-called “lab-on-a-chip” (LOC) devices emerged as one of the most important research areas. LOC devices exhibit advantages related to the use of microfluidic channels such as small sample and reagent consumption, portability, low-power consumption, laminar flow, and higher surface area/volume ratio that enhances both thermal dissipation and electrochemical kinetics. Fuel cells are electrochemical devices that convert chemical energy to electrical energy. These are considered as one of the greener ways to generate electricity because typical fuel cells produce water and heat as the main reaction byproducts. The technical challenges to develop systems at the microscale and the advantages of microfluidics exhibited an important impact on fuel cells for several reasons, mainly related to avoid inherent problems of gaseous-based fuel cells. As a result, the birth of a new type of fuel cells as microfluidic fuel cells (MFCs) took place. The first microfluidic fuel cell was reported in 2002. This MFC was operated with liquid fuel/oxidant and had the advantage of the low laminar flow generated using a “Y” microfluidic channel to separate the anodic and cathodic streams, resulting in an energy conversion device that did not require a physical barrier to separate both streams. This electrochemical system originated a specific type of MFCs categorized as membraneless also called colaminar microfluidic fuel cells. Since that year, numerous works focused on the nature of fuels, oxidants and anodic/cathodic electrocatalysts, and cell designs have been reported. The limiting parameters of this kind of devices toward their use in portable applications are related to their low cell performances, small mass activity, and partial selectivity/durability of electrocatalysts. On the other hand, it has been observed that the cell design has a high effect on the cell performance due to internal cell resistances and the crossover effect. Furthermore, current technology is growing faster than last centuries and new microfabrication technologies are always emerging, allowing the development of smaller and more powerful microfluidic energy devices. In this chapter, the application of microfluidics in membraneless fuel cells is addressed in terms of evolution of cell designs of miniaturized microfluidic fuel cells as a result of new discoveries in microfabrication technology and the use of several fuels and electrocatalysts for specific and selective applications

Estudio in silico de la afinidad de 2-Ciano-3,4- dihidro-1H-pirimidinas sobre canales de potasio dependiente de voltaje-Kᵥ+

Mediante herramientas de modelado molecular se valoró la afinidad de nuevos compuestos azaheterociclicos altamente nitrogenados, con núcleo de 2-ciano-3,4-dihidro-1H-pirimidina, sobre canales de potasio (K+). El número y naturaleza de las interacciones ligando-receptor se determinaron in silico mediante ensayos de docking dirigido y ciego sobre un canal de potasio KcsA (código PDB:1j95). Los resultados preliminares condujeron a identificar una región lipofílica común para los ligandos 1-5 y el ligando de referencia (4-aminopiridina). De manera importante, el valor de la energía libre de Gibbs (ΔG) estimado para los primeros ligandos demuestra que estos poseen una mejor afinidad hacia este sitio activo. Los resultados derivados de este estudio abren nuevas alternativas para la investigación de nuevos agentes farmacológicos con potencial aplicación en el campo de la química medicinal.Using molecular modeling tools, affinity of novel, highly nitrogenous 2-cyano-3,4-dihydro-1H-pyrimidine core-based azaheterocyclic compounds on potassium channels (K+) was explored. Quantity and nature of ligand-receptor interactions were determined in silico by directed and blind docking studies using KcsA potassium channel obtained from Protein Data Bank (code: 1j95). Preliminary results led to identify a lipophilic pocket which exhibit highly affinity toward compounds 1-5 and reference ligand (4-aminopyridine). Importantly, Gibbs free energy value (ΔG) computed for the former ligands shows that they possess the best affinity for such active site. This preliminary results support further studies for development of novel pharmacological agents with potential application in Medicinal chemistry field

The effects of electrode and catalyst selection on microfluidic fuel cell performance

A fuel cell can be best defined as an electrochemical converter of fuel and oxidant of chemical energy to electrical energy. The important components of micro fuel cells are the electrodes and catalysts because the kinetics and rates of the electrochemical reactions depend on their materials. All fuel cells consist of two electrodes: the anode, where fuel oxidation takes place, and the cathode, which is used to reduce the oxidants. The present review article highlights the use of a range of electrodes made up of different materials, a variety of catalysts that have been used in previous studies, and their fabrication materials and approaches. In this article, electrodes and catalysts are classified into two types based on the design approach applied to produce the micro fuel cell: micro fuel cell design and conventional assembly design. Most previous studies on fuel cells have demonstrated that the construction and position of the electrodes play crucial roles in improving the performance of micro fuel cells

BioVeL : a virtual laboratory for data analysis and modelling in biodiversity science and ecology

Background: Making forecasts about biodiversity and giving support to policy relies increasingly on large collections of data held electronically, and on substantial computational capability and capacity to analyse, model, simulate and predict using such data. However, the physically distributed nature of data resources and of expertise in advanced analytical tools creates many challenges for the modern scientist. Across the wider biological sciences, presenting such capabilities on the Internet (as "Web services") and using scientific workflow systems to compose them for particular tasks is a practical way to carry out robust "in silico" science. However, use of this approach in biodiversity science and ecology has thus far been quite limited. Results: BioVeL is a virtual laboratory for data analysis and modelling in biodiversity science and ecology, freely accessible via the Internet. BioVeL includes functions for accessing and analysing data through curated Web services; for performing complex in silico analysis through exposure of R programs, workflows, and batch processing functions; for on- line collaboration through sharing of workflows and workflow runs; for experiment documentation through reproducibility and repeatability; and for computational support via seamless connections to supporting computing infrastructures. We developed and improved more than 60 Web services with significant potential in many different kinds of data analysis and modelling tasks. We composed reusable workflows using these Web services, also incorporating R programs. Deploying these tools into an easy-to-use and accessible 'virtual laboratory', free via the Internet, we applied the workflows in several diverse case studies. We opened the virtual laboratory for public use and through a programme of external engagement we actively encouraged scientists and third party application and tool developers to try out the services and contribute to the activity. Conclusions: Our work shows we can deliver an operational, scalable and flexible Internet-based virtual laboratory to meet new demands for data processing and analysis in biodiversity science and ecology. In particular, we have successfully integrated existing and popular tools and practices from different scientific disciplines to be used in biodiversity and ecological research.Peer reviewe

Glassy Carbon Electrode-Supported Au Nanoparticles for the Glucose Electrooxidation: On the Role of Crystallographic Orientation

Glucose electrooxidation in alkaline solution was examined using glassy carbon electrodes modified with Au nanoparticles. Au nanoparticles were prepared following the two-phase protocol and characterized by transmission electron microscopy (TEM), UV-Vis spectroscopy, X-ray diffraction spectroscopy (XRD), and cyclic voltammetry (CV). It was found that, under the study conditions, it is possible to obtain nanoparticles between 1 and 5 nm; also it was found that the crystallographic orientation is strongly influenced by the ratio metal/thiol and to a lesser extent by the synthesis temperature. The voltammetric response for the electrocatalytic oxidation of glucose at carbon Au nanoparticle-modified electrode shows an increasing activity with nanoparticles size. Electroactivity and possibly selectivity are found to be nanoparticles' crystallographic orientation dependent. Classical electrochemical analysis shows that glucose electrooxidation is a diffusion-controlled process followed by a homogenous reaction

Morphological Effect of Pd Catalyst on Ethanol Electro-Oxidation Reaction

In the present study, three different structures with preferentially exposed crystal faces were supported on commercial carbon black by the polyol method (nanoparticles (NP/C), nanobars (NB/C) and nanorods (NR/C)). The electrocatalysts were characterized by XRD, TEM, TGA and cyclic voltammetry at three different ethanol concentrations. Considerable differences were found in terms of catalytic electroactivity. At all ethanol concentrations, the trend observed for the ethanol oxidation peak potential was preserved as follows: NB/C < NP/C< NR/C < commercial Pd/C. This result indicates that, from a thermodynamics point of view, the NB/C catalyst enclosed by Pd(100) facets presented the highest activity with respect to ethanol electro-oxidation among all of the catalysts studied