A high-speed low-voltage double-switch optical crossconnect using stress-induced bending micromirrors

A high-speed low-voltage double-switch electrostatically actuated optical crossconnect (OXC) is demonstrated using stress-induced bending micromirrors. A curved polysilicon seesaw structure substantially lowers the electrostatic operating voltage of the OXC and provides a double-switch option. Large mirror deflection angles of 13/spl deg/ (mirror elevation of 290 /spl mu/m high) and 5/spl deg/ (cantilever deflection of 90 /spl mu/m high), corresponding to low operating voltages of 25 and 18 V, could be obtained. A submillisecond switching time (<850 /spl mu/s), a low optical insertion loss (0.65 dB), and a small polarization-dependent loss (<0.08 dB) are achieved.     

Microfluidic blood-plasma separation chip using channel size filtration effect

Microsystem Technologies - Blood separation is an essential first step when performing blood tests for clinical diagnosis purposes. Such tests are increasingly performed using microfluidic systems...     

Design optimization of micromixer with square-wave microchannel on compact disk microfluidic platform

This paper presents a passive micromixer on a compact disk (CD) microfluidic platform that performs plasma mixing function. The driving force of CD microfluidic platform including, the centrifugal force due to the system rotation, the Coriolis force as a function of the rotation angular frequency and velocity of liquid. Numerical simulations are performed to investigate the flow characteristics and mixing performance of three CD microfluidic mixers with square-wave, curved and zig-zag microchannels, respectively. Of the three microchannels, the square-wave microchannel is found to yield the best mixing performance, and is therefore selected for design optimization. Four CD microfluidic micromixers incorporating square-wave PDMS microchannels with different widths in the x- and y-directions are fabricated using conventional photolithography techniques. The mixing performance of the four microchannels is investigated both numerically and experimentally. The results show that given an appropriate specification of the microchannel geometry and a CD rotation speed of 2,000 rpm, a mixing efficiency of more than 93 % can be obtained within 5 s.     

Capillary filling speed of ferrofluid in hydrophilic microscope slide nanochannels

The capillary filling speed of ferrofluid in hydrophilic nanofluidic channels is investigated under various temperature and constant magnetic field conditions. Nanochannels with depths ranging from 50 to 150 nm and widths of 30 to 200 μm are fabricated on borosilicate glass substrates using buffered oxide wet etching and glass–glass fusion bonding techniques. The capillary filling speed of the ferrofluid is measured experimentally and compared with the theoretical results predicted by the classical Washburn equation. It is found that the experimental filling speed is significantly slower than the theoretical filling speed due to the erroneous assumption in the Washburn model of a constant contact angle irrespective of the flow rate and the presence of flow obstructions. The experimental results show that the filling speed reduces with a reducing channel depth, an increasing ferrofluid concentration, a lower operating temperature and an increased filling length. However, the filling speed is enhanced in the presence of an external magnetic field.     

Design optimization of capillary-driven micromixer with square-wave microchannel for blood plasma mixing

A numerical and experimental investigation is performed into the flow characteristics and mixing performance of three microfluidic polydimethylsiloxane blood plasma mixing devices incorporating square-wave, curved and zigzag microchannels, respectively. For each device, the plasma is introduced into the microfluidic channel under the effects of capillary action alone. Of the three devices, that with the square-wave microchannel is found to yield the best mixing performance, and is therefore selected for design optimization. Four microfluidic micromixers incorporating square-wave microchannels with different widths in the x- and y-directions are fabricated using conventional photolithography techniques. The mixing performance of the four microchannels is investigated both numerically and experimentally. The results show that given an appropriate specification of the microchannel geometry, a mixing efficiency of approximately 76 % can be obtained within 4 s. The practical feasibility of the micromixer is demonstrated by performing prothrombin time (PT) tests using a total liquid volume of 4.0 μL (2.0 μL of plasma and 2.0 μL of PT reagent). It is shown that the mean time required to complete the entire PT test (including loading, mixing and coagulation) is less than 30 s.

     

Dust Deposition in Electrostatically Enhanced Fibrous Filters

A theoretical model to predict the total bed collection efficiency of a fibrous filter across which a strong electric field is applied is proposed. The fluid flow, as well as the electrostatic fields considered in the model, take into account the geometric configuration of the fibers in the filter. To predict filter efficiencies, dust-particle trajectory calculations are carried out to include inertial, interceptional, and electrostatic effects. Both the theoretical and experimental results demonstrate the dramatic increase in filtration efficiency by applying external electric fields to the filter at low Stokes numbers (St < 0.1). Experimental data were obtained by passing through the filter different pollutants such as latex aerosols (1-μm in diameter), DOP smoke, and two different kinds of solid dust generated by a specially constructed disperser. The influence of gas humidity on the separation process in the filter is also studied. The reported experimental data show good agreement with theoretical predictions, demonstrating that the physics governing the process have been properly incorporated into the model.     

Centrifuge-based micromixer with three-dimensional square-wave microchannel for blood plasma mixing

A numerical and experimental investigation is performed into the flow characteristics and mixing performance of four centrifuge-based compact disk (CD) microfluidic mixers with square-wave microchannels and different numbers and arrangements of inlet channels. Of the four micromixers, the 3 × 1 3D mixer (three inlet channels, one outlet channel, and a two-layer mixing channel) is found to yield the best mixing performance. The superior mixing performance is attributed to the formation of transverse secondary flows and a 3D stirring effect at the corners of the square-wave channel. The experimental results show that given a CD rotation speed of 1000 rpm, a mixing efficiency of more than 91 % can be obtained within 5 s. The practical feasibility of the micromixer is demonstrated by performing prothrombin time (PT) tests. It is shown that the mean time required to complete the entire PT test (including loading, mixing and coagulation) is less than 45 s.