Microfluidics a Potent Route to Sample Delivery for Non-intrusive Sensors
01 Jan 2016-pp 15-34
TL;DR: Overall, the chapter seeks to rebalance the traditional emphasis on biosensor design by highlighting the importance of controlled sample presentation as a potential route to low maintenance biosensors with improved response characteristics.
Abstract: Biosensors offer wide opportunities for threat agent analysis, but practical analytical systems require these sensors to be integrated with pre- and post analytical steps to enable simplified, seamless operation. Perhaps the most important of these steps relates to sample handling and presentation. Advances in microfluidics now offer a realistic means for simplified, practical handling with the facility for compressing existing analytical platforms in biosensing. Small volume handling can not only allow for miniaturisation, but flow at this scale enables a different type of flow profile and the a facility for direct liquid-liquid exchange. Basic flow principles in microflow are presented followed by a description of aqueous/organic flows and how they cab be used both for solute partitioning and in situ membrane formation. The potential value of miniaturised separation membranes is described, including for sample cleanup, handling and biosensor protection. Finally, examples of sensor integration into microfluidic structures are given as pointer towards future developments. Overall, the chapter seeks to rebalance the traditional emphasis on biosensor design by highlighting the importance of controlled sample presentation as a potential route to low maintenance biosensors with improved response characteristics.
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17 Feb 2006
TL;DR: In this paper, the authors demonstrate how the length and spacing of electrodes within a microchannel, and thus thickness of the diffusion layer, affects the performance of a microfluidic biofuel cell.
Abstract: Microfluidic biofuel cells exploit the lack of convective mixing at low Reynolds number to eliminate the need for a physical membrane to separate fuel from oxidant. This paper demonstrates how the length and spacing of electrodes within a microchannel, and thus thickness of the diffusion layer, affects the performance of a microfluidic biofuel cell. It was found that splitting a single electrode into two (or more) smaller electrodes and separating them by a distance equal to three times their length prevents the continuous increase in thickness of a diffusion layer. This change results in a 25% increase in maximum power density compared to a single electrode device with identical electroactive area. Furthermore, we found that the maximum current density of a microfluidic biofuel cell operated with different electrode configurations (i.e., length of cathode) closely matches that predicted by theory.
3 citations
01 Jan 2019
TL;DR: In this paper, el desarrollo de biosensores nanoplasmonicos integrados in plataformas Lab-on-a-Chip (LOC) for the detection of different analitos in tiempos real.
Abstract: La creciente demanda de plataformas de analisis que sean fiables y, al mismo tiempo, faciles de usar y compactas, que requieran un bajo consumo de muestras y proporcionen una alta sensibilidad y una respuesta en tiempo real, ha proporcionado una considerable innovacion en el diseno de los biosensores. Entre todos ellos, aquellos basados en fenomenos de resonancia de plasmon superficial (SPR) han sido objeto de un gran interes cientifico en las ultimas decadas porque aportan una alta sensibilidad y simplicidad en los esquemas de deteccion. Con el avance en las tecnicas de nanofabricacion, el desarrollo de sensores opticos basados en nanoestructuras plasmonicas ha representado una excelente via para su integracion en dispositivos Lab-on-a-chip con un reducido tamano, con la capacidad de resolver algunos de los retos actuales relacionados con los tiempos de analisis, el volumen de muestra requerido y la viabilidad de detectar varios analitos a la vez de forma multiplexada. Con el proposito de ofrecer herramientas biosensoras simples y de bajo costo, la presente Tesis Doctoral presenta el desarrollo de biosensores nanoplasmonicos integrados en plataformas Lab-on-a-Chip (LOC) para la biodeteccion multiplexada de diferentes analitos en tiempo real. El sensor desarrollado se basa en el empleo de soportes comerciales de discos Blu-Ray como un sustrato que contiene nano-rejillas para general el fenomeno de resonancia de plasmon al recubrirlos con diferentes capas metalicas a escala nanometrica. Los nanobiosensores desarrollados constituyen una alternativa muy prometedora que podrian sustituir a las tecnicas de analisis convencionales, simplificando los procesos y superando los principales retos actuales relacionados con la sensibilidad, el coste y el tiempo requerido para el diagnostico clinico.
2 citations
References
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TL;DR: The microfabrication technologies of the semiconductor industry have made it possible to integrate increasingly complex electronic and mechanical functions, providing us with ever smaller, cheaper and smarter sensors and devices, which has revolutionized ability to precisely control fluid/fluid interfaces for use in fields ranging from materials processing and analytical chemistry to biology and medicine.
Abstract: The microfabrication technologies of the semiconductor industry have made it possible to integrate increasingly complex electronic and mechanical functions, providing us with ever smaller, cheaper and smarter sensors and devices. These technologies have also spawned microfluidics systems for containing and controlling fluid at the micrometre scale, where the increasing importance of viscosity and surface tension profoundly affects fluid behaviour. It is this confluence of available microscale engineering and scale-dependence of fluid behaviour that has revolutionized our ability to precisely control fluid/fluid interfaces for use in fields ranging from materials processing and analytical chemistry to biology and medicine.
925 citations
"Microfluidics a Potent Route to Sam..." refers methods in this paper
...Microfluidics has provided a versatile platform for sample extraction and assay as described above, recently reviewed by Atencia and Beebe [40]....
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TL;DR: The reaction of species in solutions flowing laminarly inside capillaries was used as the basis for a broadly applicable method of microfabrication, applicable to the patterning of metals, organic polymers, inorganic crystals, and ceramics on the inner walls of preformed capillary, using both additive and subtractive processes.
Abstract: The reaction of species in solutions flowing laminarly (without turbulent mixing) inside capillaries was used as the basis for a broadly applicable method of microfabrication. In this method, patterning occurs as a result of transport of reactive species to interfaces within the capillary by laminar flow. A wide range of chemistries can be used to generate structures with feature sizes of less than 5 micrometers and with spatial localization to within 5 micrometers. The method is applicable to the patterning of metals, organic polymers, inorganic crystals, and ceramics on the inner walls of preformed capillaries, using both additive and subtractive processes.
797 citations
"Microfluidics a Potent Route to Sam..." refers methods in this paper
...Overall, the interest in in situ membrane formation, including our own, was stimulated by the work on microfluidics by Whiteside’s Group [51, 52]....
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TL;DR: The T-sensor as mentioned in this paper is a recently developed microfluidic chemical measurement device that exploits the low Reynolds number flow conditions in microfabricated channels, allowing measurement of analyte concentrations on a continuous basis.
Abstract: The T-sensor is a recently developed microfluidic chemical measurement device that exploits the low Reynolds number flow conditions in microfabricated channels. The interdiffusion and resulting chemical interaction of components from two or more input fluid streams can be monitored optically, allowing measurement of analyte concentrations on a continuous basis. In a simple form of T-sensor, the concentration of a target analyte is determined by measuring fluorescence intensity in a region where the analyte and a fluorescent indicator have interdiffused. An analytical model has been developed that predicts device behavior from the diffusion coefficients of the analyte, indicator, and analyte-indicator complex and from the kinetics of the complex formation. Diffusion coefficients depend on the local viscosity which, in turn, depends on local concentrations of all analytes. These relationships, as well as reaction equilibria, are often unknown. A rapid method for determining these unknown parameters by interpreting T-sensor experiments through the model is presented.
655 citations
TL;DR: The observed trends in microfluidic immunoASSay applications closely resemble the trends of general immunoassays, where large molecules are detected principally through a sandwich procedure, while competitive assays are used to detect smaller molecules.
523 citations
"Microfluidics a Potent Route to Sam..." refers background in this paper
...Immunosensors have also been under investigation at mininaturised levels, and a substantial range of surface immobilisation chemistries and flow designs are reported [69]....
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TL;DR: A topical survey of the stability, self-assembly behavior and mutual interactions of nanoparticles at fluid interfaces, focusing on sterically stabilized, charged and magnetic nanoparticles.
Abstract: Nanoparticles at fluid interfaces are becoming a central topic in colloid science studies. Unlike in the case of colloids in suspensions, the description of the forces determining the physical behavior of colloids at interfaces still represents an outstanding problem in the modern theory of colloidal interactions. These forces regulate the formation of complex two-dimensional structures, which can be exploited in a number of applications of technological interest; optical devices, catalysis, molecular electronics or emulsions stabilization. From a fundamental viewpoint and typical for colloidal systems, nanoparticles and microparticles at interfaces are ideal experimental and theoretical models for investigating questions of relevance in condensed matter physics, such as the phase behavior of two-dimensional fluids. This review is a topical survey of the stability, self-assembly behavior and mutual interactions of nanoparticles at fluid interfaces. Thermodynamic models offer an intuitive approach to explaining the interfacial stability of nanoparticles in terms of a few material properties, such as the surface and line tensions. A critical discussion of the theoretical basis, accuracy, limitations, and recent predictions of the thermodynamic models is provided. We also review recent work concerned with nanoparticle self-assembly at fluid interfaces. Complex two-dimensional structures varying considerably with the particle nature have been observed in a number of experiments. We discuss the self-assembly behavior in terms of nanoparticle composition, focusing on sterically stabilized, charged and magnetic nanoparticles. The structure of the two-dimensional assemblies is a reflection of complex intercolloidal forces. Unlike the case for bulk colloidal suspensions, which often can be described reasonably well using DLVO (Derjaguin-Landau-Verwey-Overbeek) theory, the description of particles at interfaces requires the consideration of interfacial deformations as well as interfacial thermal fluctuations. We analyze the importance of both deformation and fluctuations, as well as the modification of electrostatic and van der Waals interactions. Finally, we discuss possible future directions in the field of nanoparticles at interfaces.
414 citations
"Microfluidics a Potent Route to Sam..." refers background in this paper
...When red and white cells from blood are brought into contact with a flowing liquid-liquid interface, the red cells tend to diffuse out into the bulk phase whereas the white cells are retained because of their larger size and lower mobility; the energy minimum experienced by the cells is also a factor and is determined by cell surface area, greater for white cells [24, 25]....
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