Channel, cross-section glass

The flow velocity is linearly dependent on the electric field strength applied (veo= peo , where peo denotes the electro osmotic mobility). In glass or fused silica, linear flow velocities of 100 pm/s to 1 mm/s can be achieved with field strengths in the order of several 100 V/cm. For a typical channel cross section of 10 5 cm2 (50 x 20 pm) this results in corresponding volume flowrates in the order of 100 pl/s to 1 nl/s. 

Because wet chemical etch on glass results in an isotropic etch, the resulting channel cross section is trapezoidal or semicircular [112,136,137]. In order to form a circular channel, two glass plates were first etched with a mirror image pattern of semicircular cross section channels. Then the two plates were aligned and thermally bonded to form a circular channel [113,114,456,802,813]. 

As mentioned earlier, the melting mechanism in screw extruders was first formulated by Tadmor (29) on the basis of the previously described visual observations pioneered by Bruce Maddock. The channel cross section and that of the solid bed are assumed to be rectangular, as in Fig. 9.26. The prediction of the solid bed width profile (SBP), that is the width of the solid bed X as a function of down-channel distance z, is the primary objective of the model, which can be experimentally verified by direct observation via the cooling experiment of the kind shown in Figs. 9.20-9.25. As shown by Zhu and Chen (40), the solid bed can also be measured dynamically during operation by equipping the extruder with a glass barrel. 

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... 

FIGURE 5.16 Template scheme (top view) for solid phase sample application (SPSA) and process of performance (cross section of steps a to e) 1 — base of the device, 2 — glass plate, 3 — adsorbent layer, 4 — sample, 5 — top of the device, 6 — plunger to compress. Step a Template placed onto the preparative plate Step b Marking by means of a thin needle Step c Scraped out channel on the preparative plate Step d Filling in of the prepared mixture of sample and deactivated adsorbent Step e Compression by means of a plunger. (From Botz, L., Nyiredy, Sz., and Sticher, O., J. Planar Chromatogr, 3, 10-14, 1990. With permission.)... 

Commonly used material classes are the III-V compounds (especially when dynamic or active functions are needed), LiNbCh (because of its electro-optical properties), the indiffused glasses, the SiON-materials, the polymers and materials obtained from sol-gel technology. Last three will be treated in other chapters of this book. As an example we show the cross section of a simple channel structure based on SiON technology in Figure 6. 

Figure 4.2 A schematic diagram of an integrated polymer monolith NCE with ESI-MS detection, (a) 1, separation channel 2, double-T injector 3, ESI source 4, eluent reservoir 5, sample inlet reservoir 6, sample waste reservoir 7, eluent waste reservoir that houses a porous glass gate 8, side channel for flushing the monolithic channel and 9, ESI emitter, (b) Cross-sectional view of reservoir 7, showing the position of the semipermeable glass gate, (c) Image of on-chip junction between the separation channel and the ESI emitter [25].

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 3.46 Schematic drawing of the cross section of a mixer. A glass plate was etched with channels. It was anodically bonded with a Si wafer consisting of the oscillating diaphragm to which a PZT disk was adhered [327]. Reprinted with permission from Wiley-... 

FIGURE 4.21 Photograph of the glass microchip (5x2 cm) used for sample injection, separation, and interfacing into the MS system. To minimize the diffusion loss of the sample during separation, the connection between the side channels (leading from Q, R, T, U) and the serpentine separation channel (75 pm deep) was etched to 25 pm (one-ninth of the cross section area of the separation channel) [296]. Reprinted with permission from the American Chemical Society. 

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. 

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