Waveguide structures for efficient evanescent field coupling to zero mode waveguides

The use of waveguide structures is examined to improve the efficiency of evanescent field coupling into zero-mode waveguides. Model calculations show that waveguide excitation using diffractive structures, increases the magnitude of the evanescent electric field by an order of magnitude compared to far field excitation of the evanescent field. A more efficient excitation of fluorescent markers used in e.g. sequencing instrumentation ultimately enables real-time single molecule detection using laser systems with moderate output power

Micropumps - A literature study

A large number of actuation techniques for driving fluid through microchannels are reviewed systematically in this report. The main emphasis is given on actuation principle, structure and characteristics of the pump. Every technique has certain merits and demerits associated with it. In case of mechanical type micropumps, the moving parts make fabrication processes complex. In non-mechanical types, the fluid transport techniques relying on interfacial phenomena depend upon surface properties of the channel, the bulk force operated techniques depend on fluid properties. The former are difficult to be kept constant and reproducible and the latter limit the range of fluids which can be pumped. The ideal technique should involve no moving parts and at the same time be largely independent of fluid and surface properties

Homogeneity of multilayers produced with a static mixer

A multiflux static mixer can be used to produce multilayered structures. The flow is repeatedly cut, stretched and stacked by mixing elements in the channel of such a device. In the std. design, however, the obtained layer thicknesses are inhomogeneous. The causes for the multiflux static mixer's deviation from ideal behavior are identified by 3D numerical simulations as unequal pressure drops in the sepg. flows. Changes in the arrangement of the elements are proposed and their effects are verified by simulations and expts. A significant improvement of the layer homogeneity is achieved by introducing addnl. elements with sepg. walls at the inlets and at the outlets of the mixing elements

Magnetic bead manipulation in a sub-microliter fluid volume applicable for biosensing

Magnetic actuation principles using superparamagnetic beads suspended in a fluid are studied in this paper. An exptl. setup contg. a submicroliter fluid vol. surrounded by four miniaturized electromagnets was designed and fabricated. On the basis of optical velocity measurements, the induced behavior of single beads and ordered chains was analyzed and compared to a theor. model. This research can be used to develop new techniques for accelerated transportation in lab-on-a-chip bio-assays. [on SciFinder (R)