Combined microfluidic-micromagnetic separation of living cells in continuous flow.

This paper describes a miniaturized, integrated, microfluidic device that can pull molecules and living cells bound to magnetic particles from one laminar flow path to another by applying a local magnetic field gradient, and thus selectively remove them from flowing biological fluids without any wash steps. To accomplish this, a microfabricated high-gradient magnetic field concentrator (HGMC) was integrated at one side of a microfluidic channel with two inlets and outlets. When magnetic micro- or nano-particles were introduced into one flow path, they remained limited to that flow stream.

Construction of electrocatalytic electrodes bearing the triphenylamine nucleus covalently bound to carbon. A halogen dance in protonated aminotriphenylamines.

[reaction: see text]. The triarylamine nucleus has been attached to a carbon fiber electrode by diazotization of an aminotriphenylamine followed by electrochemical reduction. The resulting electrodes can electrocatalyze the oxidation of organic substrates.

Optical waveguiding in suspensions of dielectric particles.

An optical waveguide formed by a suspension of dielectric nanoparticles in a microchannel is described. The suspensions, chosen for their guiding and scattering properties, are silica and polystyrene particles that have diameters of 30-900 nm and are dispersed in water with volume fractions up to 10%. Changing the diameter and concentration of the particles causes the suspensions to transition from Rayleigh to Mie scattering and from single to multiple scattering.

Some recent developments in the chemical synthesis of inorganic nanotubes.

Inorganic nanotubes have been a subject of intensive research in the past decade. We recently developed a number of synthetic strategies for generating nanotubes from inorganic materials that do not have a layered structure. It is the intention of this contribution to provide a brief account of these research activities.

A low-threshold, high-efficiency microfluidic waveguide laser.

This communication describes a long (1 cm), laser-pumped, liquid core-liquid cladding (L2) waveguide laser. This device provides a simple, high intensity, tunable light source for microfludic applications. Using a core solution of 2 mM rhodamine 640 perchlorate, optically pumped by a frequency-doubled Nd:YAG laser, we found that the threshold for lasing was as low as 22 muJ (16-ns pulse length) and had a slope efficiency up to 20%.

Arrays and cascades of fluorescent liquid-liquid waveguides: broadband light sources for spectroscopy in microchannels.

This paper describes the fabrication and operation of fluidic broadband light sources for use "on-chip" in integrated microanalytical systems. These light sources consist of liquid-core, liquid-cladding (L2) microchannel waveguides with liquid cores containing fluorescent dyes, excited by incident light from an external halogen bulb. Simultaneous use of multiple fluorophores in a common solution, in a single L2 light source, is not possible, because energy transfer from fluorophores emitting at shorter wavelength to fluorophores emitting at longer wavelength is essentially complete.

Approaching zero: using fractured crystals in metrology for replica molding.

This report presents a simple and convenient method to generate nanoscale fractures (cracks) in smooth, single-crystalline Si substrates. The cracks propagated as approximately straight lines along the {100} crystal planes with controllable length defined by a stabilizing backlayer. Close to its tip, the crack presented a vertical offset of the two planes as step of smoothly decreasing height, ranging from the microscale to the atomic scale.

Dynamic control of liquid-core/liquid-cladding optical waveguides.

This report describes the manipulation of light in waveguides that comprise a liquid core and a liquid cladding (liq/liq waveguide). These waveguides are dynamic: Their structure and function depend on a continuous, laminar flow of the core and cladding liquids. Because they are dynamic, they can be reconfigured and adapted continuously in ways that are not possible with solid-state waveguides.