Time multiplexing

One way to fabricate such a reactor is by deep reactive ion etching (DRIE) with a time-multiplexed inductively coupled plasma etcher (most details on fabrication are given in [77]) [7, 77, 78]. Regions of major importance such as the retainers are etched through to avoid differences in stmctural depth which may cause uneven flow. To generate various channel depths in one design, both front-side and back-... 

The structures were etched using a time-multiplexed inductively coupled plasma etch (Figure 3.21). On the back side of such a stmctured silicon wafer holes were... 

Microfabrication involves multiple photolithographic and etch steps, a silicon fusion bond and an anodic bond (see especially [12] for a detailed description, but also [11]). A time-multiplexed inductively coupled plasma etch process was used for making the micro channels. The microstructured plate is covered with a Pyrex wafer by anodic bonding. 

The current generators and modifiers write into the current half while the previous lick s results are available to current processing. Because the output of the sum memory may feed as many as three inputs, it must be time multiplexed over a single tick, which leads to a short time available to the memory. 

Yoshitomi KJ, Jinneman KC, Weagant SD (2006) Detection of Shiga toxin genes stxl, stx2, and the +93 uidA mutation of E. coli 0157 H7/H-using SYBR Green I in a real-time multiplex PCR. Mol Cell Probes 20 31-41... 

For the deposition of mixed films or of complex alloys from two or more evaporation sources, it is necessary to control the evaporation rate of each material independently with sufficient accuracy. A single quadrupole mass spectrometer can measure the evaporation rates of the different materials in a time-multiplex process. 

The time-multiplexed mode results in a decrease in the signal-to-noise ratio, as only a fraction of the total time is available for the measurement at a particular wavelength. Shot noise will therefore increase. 

FIGURE 33.1 Time-multiplexed MEKC/CZE peptide separation chip schematic (From RockUn, R. D. et al.. Anal. Chem., 2000, 72, 5244-5249.) and (b) pseudo-gel views for chip-based separations of human and bovine hemoglobin. (From Ramsey, J. D. et al.. Anal. Chem., 2003, 75, 3758-3764.)... 

When spatial or time multiplexing is employed as a multidimensional separation strategy with a first dimension based on an electrokinetic separation mode, an inherent difficulty arises from the need for the first dimension separation channel to be intersected by one of more second dimension channels. Regardless of whether the first dimension separation is operated in a transient (e.g., CZE) or steady-state (e.g., lEF) mode, electric field lines extending into the intersecting channels result in dispersion of sample out of the first dimension channel, and ultimately to sample loss as diffusion... 

New development efforts in the area of time-multiplexed multidimensional separations may also provide real-world benefits for proteomic analysis. One of the difficulties with time multiplexing relates to sample loss resulting from the inability to fully sample all separated analyte bands within the first dimension microchannel. When a transient separation is employed in the first dimension, sample loss is inherent in this configuration due to the inability to collect fractions while the second dimension separation is proceeding. The difficulties with sample loss imposed by the serial nature of the second separation dimension could potentially be alleviated through the use of on-chip trap columns to store fractions before injection into the second dimension channel, providing parity between the desired rate of fraction acquisition and the duty cycle of the second dimension separation. Alternately, a combined time- and spatial-multiplexing scheme could be envisioned, wherein multiple second dimension separation channels sequentially sample the first dimension. 

The ability to multiplex reactions is of great importance for reducing the cost per SNP genotype and analysis time. Multiplexing at the PCR level and of the primer extension reaction is currently under investigation. The quality of the enzymatic reactions in a multiplex assay depends on the SNPs that have to be combined. The surrounding DNA sequences have an profound influence on the quality of the PCR reaction. 

In time-multiplexed deep etching (TMDE), the etching and passivation gas monomers are flowed independently one at a time during operation. First, the etch step (normally <12 s) forms a shallow isotropic trench in the silicon substrate. Second, the passivation cycle (normally <10 s) forms a protective film on all the surfaces. In the subsequent etching step, ion bombardment promotes the preferential removal of the film on the horizontal surface and further isotropic etching of silicon, allowing the profile to evolve in a highly anisotropic strucmre (Fig. 5). 

Fabrication of 3D Microfiuidic Structures, Fig. 5 Four process steps for time-multiplexed deep etching (a) isotropic etching of silicon (b) polymer passivation (c) removal of formed polymer film on the horizontal surfaces (d) further isotropic etching of silicon... 

Laermer and SchUp of Robert Bosch GmbH originally invented a fluorine-based chemistry process [5], which maintains verticality (anisotropy), by using the concept of alternate etch and passivation steps, which is also called the time-multiplexed deep etching (TMDE) [6]. 

Ayon A, Braff R, Lin CC, Sawin HH, Schmidt MA (1999) Characterization of a time multiplexed inductively coupled plasma etcher. J Electrochem Soc 146(1 ) 339-349... 

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