Channel, cross-section silicon

FIGURE 44.13 Schematic of the layout for a separation chip fabricated in standard <110>- oriented silicon with either x-shaped (I) or y-shaped (II) channel outlet, (a) Mask alignment. Reproduced from Nilsson A., et al.. Lab on a Chip, 4, 131-135, 2004. With permission from Royal Society of Chemistry, (b) Channel cross-sections. Reproduced from Nilsson A., et al.. Lab on a Chip, 4, 131-135, 2004. With permission from Royal Society of Chemistry. 

A separation chip, according to the Lund-method, is most easily made by anisotropic etching of a (100>-oriented silicon wafer. The channel mask should be aligned 45° offset to the (110)-cut phase of the wafer. Figure 44.13a, to accomplish the desired rectangular channel cross-section. Figure 44.13b. 

Silicon DRIE is independent of silicon crystal structure, and this enables fabrication of all possible shapes, in contrast to wet chemical anisotropic etching which is limited by silicon crystal planes. In microfluidics this shape freedom has implications for flow profiles, as significantly channel cross sections can be kept... 

Wu and Cheng (2003) measured the friction factor of laminar flow of de-ionized water in smooth silicon micro-channels of trapezoidal cross-section with hydraulic diameters in the range of 25.9 to 291.0 pm. The experimental data were found to be in agreement within 11% with an existing theoretical solution for an incompressible, fully developed, laminar flow in trapezoidal channels under the no-slip boundary condition. It is confirmed that Navier-Stokes equations are still valid for the laminar flow of de-ionized water in smooth micro-channels having hydraulic diameter as small as 25.9 pm. For smooth channels with larger hydraulic diameters of 103.4-103.4-291.0pm, transition from laminar to turbulent flow occurred at Re = 1,500-2,000. 

In the study by Hetsroni et al. (2006b) the test module was made from a squareshaped silicon substrate 15 x 15 mm, 530 pm thick, and utilized a Pyrex cover, 500 pm thick, which served as both an insulator and a transparent cover through which flow in the micro-channels could be observed. The Pyrex cover was anod-ically bonded to the silicon chip, in order to seal the channels. In the silicon substrate parallel micro-channels were etched, the cross-section of each channel was an isosceles triangle. The main parameters that affect the explosive boiling oscillations (EBO) in an individual channel of the heat sink such as hydraulic diameter, mass flux, and heat flux were studied. During EBO the pressure drop oscillations were always accompanied by wall temperature oscillations. The period of these oscillations was very short and the oscillation amplitude increased with an increase in heat input. This type of oscillation was found to occur at low vapor quality. 

Channel carrier a, b Microstructured silicon platelet quartz glass tube Reaction channel a cross-sectional area depth length 0.167 mm 525 pm 20 mm... 

The most common a-Si H TFT structure is the so-called inverted staggered transistor structure [40], in which silicon nitride is used as the gate insulator. A schematic cross section is shown in Figure 74. The structure comprises an a-Si H channel, a gate dielectric (SiN.v), and source, drain, and gate contacts. 

Fig. 9.8 Cross section of a silicon slot waveguide consisting of two 180 nm x 250 nm silicon channels, separated by a 50 nm gap. The solid line represents a line plot of the electric field amplitude of the horizontally polarized TE mode, taken along the horizontal midline of the waveguide...

Figure 2. Flow cell (excluding pump and titration cell). Left Front view. Right Cross section along center line. I. Perspex cover. 2. Outlet tube (back to titration cell). 3. Flow channel. 4. Counter electrode (platinum). 5. Metal plate with cut edge exposed in the channel. 6. Seal of molded silicone rubber. 7. Piston for removal of air fix>m reference electrode compartment. 8. Reference electrode compartment. 9. Capillary holes connecting 8 to 3.10. Inlet tube (from titration cell). II. Reference electrode (Ag/AgCI, sat. KCI). (Reprinted from Ref. 3, with kind permission from Elsevier Science Ltd., Kidlington, Oxford, UK.)...

In Fig. 9, the cathode block (4) of stainless steel includes inlet and outlet channels (6) that are each cormected by 6 boreholes for uniform flow distribution to the cathode surface (details see cross section 7). The anode (2) is a platinum foil of 18 cm active area with the brass cover plate (1) as current feeder. The electrode distance is given by the sealing gasket (3), for example, silicon rubber of 0.2-1 mm [85]. 

Guijt et al. [69] reported four-electrode capacitively coupled conductivity detection in NCE. The glass microchip consisted of a 6 cm etched channel (20 x 70 pm cross-section) with silicon nitride covered walls. Laugere et al. [70] described chip-based, contactless four-electrode conductivity detection in NCE. A 6 cm long, 70 pm wide, and 20 pm deep channel was etched on a glass substrate. Experimental results confirmed the improved characteristics of the four-electrode configuration over the classical two-electrode detection set up. Jiang et al. [71] reported a mini-electrochemical detector in NCE,... 

FIGURE 8.6 The cross section of a weir-type filter (not to scale). The channels in the silicon substrate are anisotropically etched using EPW. This gives the characteristic V-shaped grooves. This profile is critical to preventing surface tension lock. The barrier or weir is etched in a different step from the channels and can be anywhere from 0.1 pm to a few micrometers from the lid. The lid is Pyrex glass and is attached to the substrate by anodic bonding [836]. Reprinted with permission from Elsevier Science. 

The gas mixture used to etch the silicon consists of SF6 and 02 SF6+ ions and oxygen radicals are generated in the plasma. Photoresist is the masking layer employed in DRIE. Aspect ratios up to 50 are possible. The channels can be formed on any pattern and will have a rectangular cross section. A two-sided process or two-stage masking is used if holes are required in combination with cavities. Figure 2.13 shows examples. 

Q cm in 10 M HF at 100 mA cm [94]. The primary pores are highly oriented and channel like, propagating perpendicular to the surface in the [100] direction. The pores are polygonal in cross-section and do not exhibit any obvious anisotropy. The pores are packed closely together with interpore regions of silicon on the order of 100 A and a pore density of 2xl0 °cm. ... 

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