Single-Molecule Fluorescence Observed with Mercury Lamp Illumination

We demonstrate that it is possible to observe single fluorescent molecules using a standard fluorescence microscope with mercury lamp excitation and an inexpensive cooled charge-coupled device (CCD) camera. With this equipment, we have been able to observe single molecules of tetramethyl-rhodamine, rhodamine 6G, fluorescein isothiocyanate and green fluorescent protein. Immobilized molecules were observed both in air and in aqueous solution

Single-Molecule Fluorescence Observed with Mercury Lamp Illumination

We demonstrate that it is possible to observe single fluorescent molecules using a standard fluorescence microscope with mercury lamp excitation and an inexpensive cooled charge-coupled device (CCD) camera. With this equipment, we have been able to observe single molecules of tetramethyl-rhodamine, rhodamine 6G, fluorescein isothiocyanate and green fluorescent protein. Immobilized molecules were observed both in air and in aqueous solution

Where Nanophotonics and Microfluidics Meet

A new generation of photonic devices has recently emerged that relies on using geometries of sub-wavelength microstructures within a high refractive index contrast materials system. These geometries are used to confine and manipulate light within very small volumes. High optical field densities can be obtained within such structures, and these in turn can amplify optical nonlinearities. Moreover, many of these structures, as for example photonic crystals and slotted waveguides, can be engineered for the efficient localization of light within the low-index regions of high index contrast microstructures. When such structures are back-filled nonlinear polymers or liquids, devices can be tuned and novel phenomena can be observed. In particular, such devices are very interesting when constructed from silicon on insulator (SOI) material in which the optical waveguide also serves as a transparent electrical contact. Here we show examples of the design, fabrication and testing of optical microstructures in which the electro-optic (χ2) and photorefractive (χ3) nonlinearities are used for electro-optic tuning, frequency mixing, optical rectification, and high-speed switching of light

Where Nanophotonics and Microfluidics Meet

A new generation of photonic devices has recently emerged that relies on using geometries of sub-wavelength microstructures within a high refractive index contrast materials system. These geometries are used to confine and manipulate light within very small volumes. High optical field densities can be obtained within such structures, and these in turn can amplify optical nonlinearities. Moreover, many of these structures, as for example photonic crystals and slotted waveguides, can be engineered for the efficient localization of light within the low-index regions of high index contrast microstructures. When such structures are back-filled nonlinear polymers or liquids, devices can be tuned and novel phenomena can be observed. In particular, such devices are very interesting when constructed from silicon on insulator (SOI) material in which the optical waveguide also serves as a transparent electrical contact. Here we show examples of the design, fabrication and testing of optical microstructures in which the electro-optic (χ2) and photorefractive (χ3) nonlinearities are used for electro-optic tuning, frequency mixing, optical rectification, and high-speed switching of light

Acute Drug Treatment in the Early C. elegans Embryo

Genetic and genome-wide RNAi approaches available in C. elegans, combined with tools for visualizing subcellular events with high-resolution, have led to increasing adoption of the early C. elegans embryo as a model for mechanistic and functional genomic analysis of cellular processes. However, a limitation of this system has been the impermeability of the embryo eggshell, which has prevented the routine use of small molecule inhibitors. Here, we present a method to permeabilize and immobilize embryos for acute inhibitor treatment in conjunction with live imaging. To identify a means to permeabilize the eggshell, we used a dye uptake assay to screen a set of 310 candidate genes defined by a combination of bioinformatic criteria. This screen identified 20 genes whose inhibition resulted in >75% eggshell permeability, and 3 that permeabilized embryos with minimal deleterious effects on embryo production and early embryonic development. To mount permeabilized embryos for acute drug addition in conjunction with live imaging, we combined optimized inhibition of one of these genes with the use of a microfabricated chamber that we designed. We demonstrate that these two developments enable the temporally controlled introduction of inhibitors for mechanistic studies. This method should also open new avenues of investigation by allowing profiling and specificity-testing of inhibitors through comparison with genome-wide phenotypic datasets

Synergism between particle-based multiplexing and microfluidics technologies may bring diagnostics closer to the patient

In the field of medical diagnostics there is a growing need for inexpensive, accurate, and quick high-throughput assays. On the one hand, recent progress in microfluidics technologies is expected to strongly support the development of miniaturized analytical devices, which will speed up (bio)analytical assays. On the other hand, a higher throughput can be obtained by the simultaneous screening of one sample for multiple targets (multiplexing) by means of encoded particle-based assays. Multiplexing at the macro level is now common in research labs and is expected to become part of clinical diagnostics. This review aims to debate on the “added value” we can expect from (bio)analysis with particles in microfluidic devices. Technologies to (a) decode, (b) analyze, and (c) manipulate the particles are described. Special emphasis is placed on the challenges of integrating currently existing detection platforms for encoded microparticles into microdevices and on promising microtechnologies that could be used to down-scale the detection units in order to obtain compact miniaturized particle-based multiplexing platforms

Microfluidic vias enable nested bioarrays and autoregulatory devices in Newtonian fluids

We report on a fundamental technological advance for multilayer polydimethylsiloxane (PDMS) microfluidics. Vertical passages (vias), connecting channels located in different layers, are fabricated monolithically, in parallel, by simple and easy means. The resulting 3D connectivity greatly expands the potential complexity of microfluidic architecture. We apply the vias to printing nested bioarrays and building autoregulatory devices. A current source is demonstrated, while a diode and a rectifier are derived; all are building blocks for analog circuitry in Newtonian fluids. We also describe microfluidic septa and their applications. Vias lay the foundation for a new generation of microfluidic devices